Coating processes – Direct application of electrical – magnetic – wave – or... – Electromagnetic or particulate radiation utilized
Patent
1999-06-23
2000-11-14
Beck, Shrive
Coating processes
Direct application of electrical, magnetic, wave, or...
Electromagnetic or particulate radiation utilized
427493, 427498, 427512, 427116, C08J 704, B05D 512
Patent
active
061467170
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for impregnating components with polymerizable compositions which are liquid at room temperature or can be liquefied by heating and are curable by combined use of heat and high-energy radiation.
Processes for impregnating components with polymerizable compositions which are curable by means of heat and/or high-energy radiation are known.
DE-A-40 22 235 and DD-A-295 056 propose, after impregnation of the component, to first cure the surfaces using UV radiation and to then cure the interior of the components by application of heat. Although such processes do reduce the vaporization losses, the losses are still relatively high as a result of the high proportions of volatile, nonpolymerizable monomers in the interior of the components. Ways of influencing the non-uniform impregnant distribution in the component are not mentioned in these publications.
EP-A-0 643 467 proposes improving the impregnant distribution in the component by achieving pregelling and fixing of the impregnant and thermal curing during impregnation by means of coil heating. At the same time as the thermal curing on the windings or else after thermal curing on the windings, those places in the components which have not been reached by the heating of the windings are to be cured with high-energy radiation, preferably UV radiation. A disadvantage of this process is that only partial curing is achieved by heating via the windings and full curing is then carried out using radiation. Since all known components have places which are not reached by partial thermal curing and are in a shadowed region during post-curing using radiation, components which have been treated according to EP-A-0 643 467 always have regions in which the impregnant has been only insufficiently cured. This results in undesired emissions from these regions and the impregnant cannot fully satisfactorily fulfill its functions in those places. Another procedure proposed in EP-A-0 643 467 according to which the thermal curing is followed by curing with high-energy radiation seems not to be appropriate industrially since such curing after full thermal curing of the places in the component not reached in the first partial curing step, regardless of whether it is carried out by sufficiently long electric heating of the winding or by other application of heat, brings no discernible advantages. Furthermore, EP-A-0 643 467 provides no teachings regarding the use of the process in the impregnation techniques which are claimed generally. Thus, pregelling by heating of the windings during impregnation is not appropriate because the voids are filled in an undefinable manner. Preheating the windings to lower the viscosity and thus to accelerate the filling is known prior art, eg. in the various dipping and flooding processes in which the components are heated in order to lower the viscosity and thus achieve better and more rapid filling. Heating to the gelation point during impregnation has the opposite effect, namely undefined filling of the voids as a result of gelation.
The procedure of gelation during impregnation is only conceivable when the impregnant properties and all process parameters are absolutely constant, but it always remains very susceptible to problems. Even in the case of small deviations, inner regions of the windings can be screened by pregelled impregnant and thereby remain unfilled. The preheating of the windings proposed in EP-A-0 643 467, for example to 180.degree. C., leads on immersion to undefined gelation on the hot coil and very nonuniform distribution of the impregnant in the component. A lesser degree of preheating does reduce the impregnant temperature in the immediate vicinity of the winding and thereby aids the impregnation process, but as soon as the preheating temperature is increased to the point at which gelation occurs during impregnation this also results in nonuniform distribution of the impregnant.
The polymeric constituents of known impregnation, sealing and coating compositions for electrical components, for exa
REFERENCES:
patent: 3914467 (1975-10-01), Akao et al.
patent: 3937855 (1976-02-01), Gruenwald
patent: 4247578 (1981-01-01), Skinner et al.
patent: 4649640 (1987-03-01), Ito et al.
patent: 4792462 (1988-12-01), Smith et al.
patent: 5780117 (1998-07-01), Swartz et al.
patent: 5932297 (1999-08-01), Tatsuno et al.
patent: 5935661 (1999-08-01), Biller et al.
Hawley, Gessner G., The Condensed Chemical Dictionary, 10th ed., p. 340.
Blum Rainer
Eichhorst Manfred
Hegemann Gunter
Lienert Klaus-Wilhelm
Beck Shrive
Kolb Jennifer
Schenectady International Inc.
LandOfFree
Method of impregnating components does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of impregnating components, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of impregnating components will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2062980