Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1982-07-20
1985-10-22
Bleutge, John C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
427399, 525111, 525121, C08F 800, B05D 500
Patent
active
045489890
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
Fluorocarbon polymer compositions are known for use as sealants and adhesives for articles intended to be subjected to high temperature. It is understood that in aircraft which fly at speeds in excess of the speed of sound, heat generated in such areas as wings (which may include fuel tanks) and bodywork adjacent the engine, is sufficient to produce surface temperatures at metal surfaces of the aircraft in excess of 150.degree. C. Coatings, seals, and adhesive bonds in such aircraft are also likely to be exposed to fuels and oils and atmospheric moisture.
BACKGROUND ART
Certain fluorocarbon polymer compositions have found use for example as sealants in the manufacture and repair of supersonic aircraft. Liquid curable compositions for this application can be formulated which cure to an elastomeric state over a period of a few days at ambient temperatures of about 18.degree. to 20.degree. C. or more quickly at higher temperatures. For example, there are disclosed in UK patent specification No. 1037672 two-part curable fluorocarbon polymer compositions comprising a copolymer of hexafluoropropylene with vinylidene fluoride, magnesium oxide, amines, 1:6 hexane-dithiol and a silane. The dithiol is a significantly malodorous material, but for many years has been regarded as an important ingredient for the curing of the polymer. Presence of a dithiol in the composition has been regarded as essential in order to achieve compositions which have an adequate "work life" when mixed and are capable of curing to an elastomeric state at room temperature, and of adhering satisfactorily to materials used in aircraft construction for example alloys of titanium and chromate treated or epoxy coated aluminium alloys. Curable compositions using fluorocarbon polymer and dithiol have been used for many years, but it is believed that their offensive odour has inhibited more extensive use of the compositions, especially for example where the composition is required to be mixed or applied in a confined working space, or applied to large areas of a workpiece.
Odourless compositions are highly desirable, coupled with the ability to remain usable for a desired length of time after mixing and then become cured to an elastomeric state within an acceptably short time, without application of heat. Not only is it desirable to identify a composition of low odour, and suitable cure characteristics, but also it is necessary to provide a means of achieving good adhesion to metal alloys (for example ones based on titanium or aluminium) which are used in the aircraft construction industry, without promoting unacceptable corrosion of the metal alloys. As far as we are aware, prior to the present invention, no composition has been proposed which satisfied these requirements.
DISCLOSURE OF THE INVENTION
We have now found that an odourless room temperature curable composition having desirable work life and with acceptable non-corrosive properties, may comprise a fluorocarbon copolymer, an organic solvent for the copolymer, a metal oxide, an epoxy resin and selected diamino silane.
The present invention provides in one of its aspects a room temperature curable composition comprising a fluorocarbon copolymer and a metallic oxide, characterised in that the composition is at least substantially free of thiol and comprises a compound having epoxy groups, and as cross-linking agent a diamino silane according to the general formula (i) namely ##STR3## in which
R.sub.1 is an aliphatic hydrocarbon residue having 1 to 10 carbon atoms,
R.sub.2 is an aliphatic hydrocarbon residue having 1 to 10 carbon atoms, and
R.sub.3, R.sub.4 and R.sub.5 are the same or different monovalent aliphatic hydrocarbon residues having 1 to 5 carbon atoms.
A composition according to the invention is preferably shipped and stored as two separate storage stable components (A) and (B) for admixture at the time of use. Preferably the component (B) consists solely of the cross-linking agent, and the components (A) and (B) are mixed in appropriate proportions to yield
REFERENCES:
patent: 4338376 (1982-07-01), Kritzler
patent: 4369279 (1983-01-01), Emerick
Lee and Neville; "Handbook of Epoxy Resins", 15-13 and 22-17.
Allen Christopher M.
Hincklieff Ian R.
Bleutge John C.
Carrillo A. L.
Meegan Owen J.
USM Corporation
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