Vapor deposition of solid oligomers
View Patent ↗A monomer is selected to produce a polymeric film having desirable characteristics for a particular application. The monomer is ppolymerized under controlled conditions to produce a solid oligomer having those characteristics at a molecular weight suitable for evaporation under vacuum at a temperature lower than its thermal decomposition temperature. The process of polymerization to produce the oligomer is carried out under conditions that yield a finite molecular-chain length with no residual reactive groups. The solid oligomer so produced is extruded as a film onto a revolving drum ( 38 ) in the evaporation section ( 40 ) of a vapor deposition chamber, and then cryocondensed on a cold substrate ( 44 ) to form a solid film having the same characteristic selected in the solid oligomer constituting the starting material. As a result of the initial complete reaction to produce the oligomer, the thin-film product does not contain unreacted groups and all attendant disadvantages are avoided.
1. A process for forming a solid thin-film layer of oligomeric material in a vapor deposition unit operating at a predetermined pressure, a predetermined evaporator temperature, and a predetermined condenser temperature, the process comprising the following steps:
(a) polymerizing a monomer to obtain a solid oligomer thereof having a vaporization temperature at said predetermined pressure that does not exceed said predetermined evaporator temperature, and having a decomposition temperature at said predetermined pressure that exceeds said predetermined evaporator temperature;
(b) flash evaporating the solid oligomer in said vapor deposition unit to produce a vapor at said predetermined pressure and evaporator temperature; and
(c) cryocondensing the vapor to produce a solid oligomer in thin-film form in the absence of irradiation during the flash evaporating and cryocondensing steps;
wherein said monomer is a bicycloaliphatic component used to prepare a heat-sealable coating and said oligomer has a molecular weigh not to exceed about 1200.
2. A process for forming a solid thin-film layer of oligomeric material in a vapor deposition unit operating at a predetermined pressure, a predetermined evaporator temperature, and a predetermined condenser temperature, the process comprising the following steps:
(a) polymerizing a monomer to obtain a solid oligomer thereof having a vaporization temperature at said predetermined pressure that does not exceed said predetermined evaporator temperature, and having a decomposition temperature at said predetermined pressure that exceeds said predetermined evaporator temperature;
(b) flash evaporating the solid oligomer in said vapor deposition unit to produce a vapor at said predetermined pressure and evaporator temperature; and
(c) cryocondensing the vapor to produce a solid oligomer in thin-film form in the absence of irradiation during the flash evaporating and cryocondensing steps;
wherein said cryocondensing step is conducted over a continuous substrate passing through the vapor deposition unit.
3. Apparatus for vaporizing a solid oligomeric material in a vapor deposition unit, comprising the following combination of components:
a vapor deposition chamber;
an extruder operable at controlled throughput for delivering a predetermined rate of said oligomeric material at an output of the extruder;
a heater adapted to melt the solid oligomeric material and produce a melted form thereof prior to passage through said output of the extruder; and
a nozzle coupled to said output of the extruder and adapted to release a film of said melted form of the oligomeric material into said vapor deposition chamber;
further comprising a heated rotating drum having a surface adapted to receive said film upon release from the nozzle.
4. The apparatus of claim 3 , wherein said heater is operably coupled to the extruder.
5. The apparatus of claim 3 , wherein said nozzle includes a slit of a predetermined width defining a thickness for said film.
6. The apparatus of claim 5 , wherein said predetermined width is less than about 2 mm.