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
1998-11-20
2000-05-09
Yoon, Tae
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...
524 27, 524 35, 524492, 524493, 524588, C08K 320, C08L 8300, C08L 6104, C08L 100
Patent
active
060605480
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a capping cement for electric lamps.
I. PRIOR ART
A capping cement of this kind is disclosed, for example, in European Patent EP 0 261 722. The capping cement described in that document consists of a mixture of natural resins and synthetic resins, fillers and solvents and further additives. Natural resins used are shellac and rosin. Synthetic resins mentioned are silicone resin and phenol-formaldehyde resin. The filler component consists of calcium carbonate, and the solvent is ethanol. In addition, this cement includes hexamethylenetetramine as an additive.
II. SUMMARY OF THE INVENTION
The object of the invention is to provide a capping cement for electric lamps which has a minimal resin content, is inexpensive, and provides the lamp cap with satisfactory resistance to removal by twisting.
This object is achieved in accordance with the invention claimed herein. The low resin content is made possible essentially as a result of the exclusive use of calcite in crystalline form, which has a comparatively low absorbency, as the filler. The use of calcite having a particle size of between 0.1 .mu.m and 700 .mu.m has proven particularly advantageous, the average particle size of the calcite advantageously being about 200 .mu.m and the calcite advantageously possessing an average density of 2.7 g/cm.sup.3. The resin content of the capping cement of the invention is not more than 16 percent by weight. In the preferred embodiments, indeed, it is below 13 percent by weight. The satisfactory resistance of the capping cement, especially a satisfactory resistance to removal by twisting in the case of lamps equipped with screw and bayonet caps, is made possible by using a mixture of natural resins and synthetic resins, the natural resin component amounting to not more than 5 percent by weight and the synthetic resin component not more than 11 percent by weight of the capping cement. A ratio of the natural resin weight proportions to the synthetic resin weight proportions of between 0.1 and 0.5, and with particular advantage between 0.12 and 0.4, has proven advantageous in this context. By virtue of the low resin content and the combination of natural resins, such as shellac and rosin, with synthetic resins, such as phenolic resin and silicone resin, the capping cement of the invention is also inexpensive. Advantageously, the synthetic resin component of the capping cement of the invention contains only phenolic resins and silicone resins. In comparison with the prior art, the capping cement of the invention consists of only a few components.
The invention is illustrated below with reference to three preferred embodiments.
III. DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the particularly preferred first embodiment, the synthetic resin component of the capping cement of the invention consists of 8.1 percent by weight of phenolic resin of type K 0791 from Bakelite and 0.7 percent by weight of silicone resin of type 6-2230 from Dow Corning. The natural resin component of this capping cement consists of 2.5 percent by weight of rosin and 0.8 percent by weight of shellac. The filler component is formed by 74.8 percent by weight of calcite of type JP/LM from Merkle GmbH and 8.0 percent by weight of calcite of type Nofacal Z from Bayerische Farben- und Mineralwerke. The particle size of the crystalline calcite lies between 0.1 .mu.m and 700 .mu.m. The average particle size, by which is meant what is known as the D50 value, of the calcite is approximately 200 .mu.m. The average density of the calcite is 2.7 g/cm.sup.3. The solvents used are 1.1 percent by weight of isobutanol and 3.7 percent by weight of ethanol. In addition, the capping cement of the first embodiment of the invention also includes 0.3 percent by weight of a 1.8 percent strength solution of fuchsine red as dye. In this case, the synthetic resin content amounts in total to 8.8 percent by weight and the natural resin content in total to 3.3 percent by weight, resulting in an overall resin content of 12.1 percent by
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Patent Abstracts of Japan, vol. 008, No. 256 (E-280), Nov. 22, 1984 & JP 59 128752 A (Karupu Kogyo KK), Jul. 24, 1984, siehe Zusammenfassung.
Patent Abstracts of Japan, vol. 014, No. 557 (E-1011), Dec. 11, 1990, & JP 2 239540 A (Toshiba Lighting & Technol Corp) Sep. 21, 1990, siehe Zusammenfassung.
Grant & Hackh's "Chemical Dictionary" 5th Edition, p. 354, 1987.
Schirmer Rainer
Schoenwetter Johann
Wilhelm Armin
Bessone Carlo S.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
Wyrozebski Katarzyna
Yoon Tae
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