Aromatic fluoro-polyimide adhesives

#The present invention is concerned with fluoropolyimide adhesives and is a patent of addition to UK patent specification No. 1,373,907.

#UK Pat. No. 1,373,907, the entire disclosure of which is incorporated herein by reference, discloses aromatic polyimide copolymers, or their obvious poly(amic acid) equivalents (as hereinafter defined) which includes the repeating unit ##STR3## wherein X is --(CF.sub.2).sub.n -- or a mixture of --(CF.sub.2).sub.n -- and --CO where n is an integer from two to eight inclusive and R represents divalent aromatic groups having the formulae: ##STR4## wherein Y is a divalent linking atom or group and is advantageously --O--, --S--, --CO--, --SO.sub.2 --, --CONH--, --CH.sub.2 --, or --(CF.sub.2).sub.m -- where m is an integer from two to eight inclusive and about 10 to 50 moles % of said divalent aromatic groups have at least one direct nuclear substituent selected from organocarbonylamino groups, preferably acylamino groups, a carboxylic acid group, and alkoxy-carbonyl groups. When only a single direct nuclear substituent is present it is preferably an acylamino group and when two direct nuclear substituents are present they are a first direct nuclear substituent which is an organocarbonylamino group, preferably acylamino and a second direct nuclear substituent which is a carboxylic acid group or an alkoxycarbonyl group, the said first and second direct nuclear substituents being present in substantially equimolar proportions, and being attached to separate aromatic nuclei.

#Advantageously aromatic polyimide copolymers disclosed in UK patent specification No. 1,373,907 are represented by the formula: ##STR5## wherein n is an integer from two to eight inclusive, Y is a divalent linking atom or group and is advantageously --O--, --S--, --CO--, --SO.sub.2 --, --CONH--, --CH.sub.2 --, or --(CF.sub.2).sub.m -- where m is an integer from two to eight inclusive and the ratio x:y is within the range 19:1 to 7:3 and preferably n = 3, Y is --O-- and the ratio x:y is 17:3.

#The diamines, EDAB(0.6084g, 0.0034 mole), DAA(0.5575g, 0.0034 mole) and DPE(3.1537g, 0.0158 mole) were dissolved in approximately 3/4 of the total of 105gDMAC with stirring at room temperature to yield a clear, colourless solution. DBDA(10.0045g, 0.0225 mole) was added portionwise through a powder funnel with a good nitrogen flow, the solution being protected from atmospheric moisture. Addition of the DBDA caused a slight exothermic reaction, the initially formed yellow colour fading quite rapidly to a straw yellow colour. The remaining solids were washed in with the remaining DMAC. The reaction mixture then contained 12% by weight of solids. Stirring was continued for about 3 hours at the end of which time the inherent viscosity, .eta..sub.inh, measured on a 0.1% by weight solution in DMAC was 1.3 dl/g.

#The poly(amic acid) was stored refrigerated.

#Arsenic thioarsenate (0.2875g, 2% by weight of solids in solution) was thoroughly wetted by DMAC (ca 11 ml) and then added to the vigorously stirred poly(amic acid) solution. Stirring was continued for between 1/2 and 1 hour to ensure thorough dispersal of the arsenic thioarsenate particles.