Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1998-05-27
2000-08-01
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524423, 524425, 524447, 524451, 524496, C08K 300
Patent
active
060968192
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to reflector blanks comprising a synthetic material, on whose surface portions, intended for the reflection of beams, a coating of metal is applied. It is within the scope of prior art (cf. Duroplaste, Kunststoff-Handbuch, Vol. 10, Hanser-Verlag, Second Edition, 1988, pp. 318-319) to produce the blanks, i.e. the nonmetallized reflectors through injection molding or transfer molding of BMC molding compounds. BMC molding compounds are plastic compounds of unsaturated polyester resin dissolved in styrene, curing agents, additives and reinforcement fibers.
However, the obtained blanks have insufficient surface quality. The surfaces have peak-to-valley heights of 0.2 to 0.5 .mu.m. They are therefore improved through additional lacquer/varnish treatment before the metal coating is applied. This permits attaining peak-to-valley heights of <1 .mu.M (cf. DE-C 41 12 144).
Since the lacquer/varnish treatment of the blanks is an undesirable process step, attempts are made, to produce blanks with improved surface quality which can be metallized directly.
It is known for example from EP-A 0 634 605 to produce reflectors with high surface quality by injection molding of an epoxy resin molding compound which comprises as preferred fillers a quartz/kaolin mixture and wollastonite. Apart from the fact that, due to the hard filler materials, these molding compounds lead to increased tool and machine wear our own work showed that such molding compounds show a shrinkage of approximately 0.7 to 1% during the curing. In addition, a surface peak-to-valley height of only 0.1 .mu.m is obtained.
It is therefore the task of the invention to describe a reflector blank in which the application of the metal coating on the synthetic material blank (metallization) can take place without intermediate surface improvement, in which the blank during the curing experiences markedly decreased shrinkage and attains a surface peak-to-valley.
U.S. Pat. No. 5,760,159 teaches one to produce reflector blanks meeting the above listed requirements of polyester molding compounds free of styrene and fibers.
It was found that molding compounds based on thermosetting polymers which are cured by condensation reactions are also suitable for the production of reflector blanks if they are free of fibers and if the filler substances have a mean particle size of less than 50 .mu.m, preferably less than 10 .mu.m. It is therein especially surprising that the compounds, although cured by condensation reaction, have a surface peak-to-valley height of less than 0.1 .mu.m and only a low shrinkage of less than 0.7%, while the epoxy resin molding compounds, known from EP-A 0 634 605 and curing by addition reaction, have greater surface peak-to-valley heights and stronger shrinkage.
The reflector blanks according to the invention are therefore accurate to dimensional measurements, have sufficient strengths and a surface peak-to-valley height of less than 0.1 .mu.m.
The molding compounds used for the production of these reflector blanks comprise one of more duroplastic resin(s), curing by condensation reaction, fillers and additives, as well as potentially curing agents or curing accelerators.
It was found that such molding compounds, after they have been molded and cured, show an extremely low degree of shrinkage of approximately <0.3 to 0.6% and high surface quality with peak-to-valley heights of <0.1 to <0.05 .mu.m if the fraction of fillers is at least 45 wt % and the fillers have a mean grain size of less than 50 .mu.m, preferably of less than 10 .mu.m. These molding compounds are formed in a manner known per se through injection molding or transfer molding processes and cured, and in the process blanks are produced with an average surface peak-to-valley height of less than 0.5 .mu.m, even of less than 0.1 .mu.m. The application of a metal coating on the surface which is intended to be reflective, takes place in a manner known per se such as is also used in reflectorizing processes according to the described prior art, howeve
REFERENCES:
Chemical Abstracts, vol. 99, No. 4, Jul. 25, 1983, Abstract No. 23550, XP002054338.
Chemical Abstracts, vol. 105, No. 8, Aug. 25, 1986, Abstract No. 61763, XP002054339.
Chemical Abstracts, vol. 94, No. 6, Feb. 9, 1981, Abstract No. 31581, XP002054340.
Glagla Roland
Poch-Parramon Jose
Bakelite AG
Cain Edward J.
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