Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1980-09-08
1981-07-28
Cockeram, H. S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
252182, 528 44, 528 45, 560 26, C08G 1880, C08G 1850, C08G 1854
Patent
active
042810892
ABSTRACT:
Polyurethane prepolymers having free isocyanate groups are treated with polyfunctional isocyanate-blocking agents to cause branching prior to or simultaneously with the addition of a curing diol. The composition containing the curing diol is molded in a conventional equipment at a conventional temperature, e.g., 100.degree.-120.degree.C. The resulting shaped article can be demolded in a fraction of the time required in the absence of the blocking agent. The shaped article is then post-cured within a temperature range of about 25.degree.-150.degree. C., during which time the curing diol, if present in sufficient amount, displaces the blocking agent and forms a cured, linear polyurethane. A typical suitable blocking agent is a substantially uncrosslinked phenol/formaldehyde resin. The curable composition can be prepared in one step from the diisocyanate, glycol, and blocking agent; and a composition containing all the components, including the curing diol, can be prepared in one or more steps. If a nonbasic blocking agent is used in the presence of the curing diol, it is recommended to use a tertiary amine catalyst to selectively catalyze the blocking, rather than the curing, reaction. The cured linear polyurethanes have good physical properties, comparable with those of the prior art polyurethane elastomers. Partly crosslinked cured polyurethanes find utility where resistance to organic liquids is important.
REFERENCES:
patent: 3069379 (1962-12-01), Lavin et al.
patent: 3242230 (1966-03-01), Habib
patent: 3345237 (1967-11-01), Shaw
Cockeram H. S.
E. I. Du Pont de Nemours and Company
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