Durable glass elements
AssigneeMinnesota Mining and Manufacturing Company
InventorsChi F. Tung, Benjamin T. Fellows
Life of this patent
Estimating the term…
Abstract
Glass microspheres and other glass elements based on B.sub.2 O.sub.3, BaO, SiO.sub.2 and TiO.sub.2 have an improved combination of crushing strength, index of refraction, and, especially in some formulations, chemical resistance. The microspheres are especially adapted for use as retroreflective elements in pavement markings.
Claims14
Durable visibly transparent clear microspheres less than about 2 millimeters in diameter, containing no more than about 5 weight-percent scattered crystallinity, and adapted for use as a reflective element in a pavement marking, said microspheres being formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________ B.sub.2 O.sub.3 5-20 TiO.sub.2 20-40 BaO and/or SrO 10-35 Alkali-metal oxide 0-15 selected from Na.sub.2 O and K.sub.2 O SiO.sub.2 25-40 All other ingredients 0-15;
- ______________________________________
- said glass being essentially free of CaO, and containing no more than 10 weight-percent ZnO;
- and said glass having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
Durable visibly transparent clear microspheres between about 0.25 and 2 millimeters in diameter, containing no more than 5 weight-percent scattered crystallinity, and formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________ B.sub.2 O.sub.3 10-20 TiO.sub.2 25-35 BaO and/or SrO 15-25 Alkali-metal oxide 2-10 selected from Na.sub.2 O and K.sub.2 O SiO.sub.2 25-35 NaF 1-3;
- ______________________________________
- said glass being essentially free of CaO and containing no more than 10 weight-percent ZnO, having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
Durable visibly transparent clear microspheres less than about 2 millimeters in diameter, containing no more than 5 weight-percent scattered crystallinity, and adapted for use as a reflective element in a pavement marking, said microspheres being formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________ B.sub.2 O.sub.3 10-20 TiO.sub.2 20-40 BaO and/or SrO 10-35 Alkali-metal oxide 0-15 selected from Na.sub.2 O and K.sub.2 O SiO.sub.2 20-40 All other ingredients 0-15;
- ______________________________________
- said glass being essentially free of CaO, and containing no more than 10 weight-percent ZnO;
- and said glass having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
Durable visibly transparent clear microspheres between about 0.25 and 2 millimeters in diameter, containing no more than 5 weight-percent scattered crystallinity, and formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________ B.sub.2 O.sub.3 5-20 TiO.sub.2 25-50 BaO and/or SrO 15-25 Alkali-metal oxide 2-15 selected from Na.sub.2 O and K.sub.2 O SiO.sub.2 25-40 All other ingredients 0-15;
- ______________________________________
- said glass being essentially free of CaO and containing no more than 10 weight-percent ZnO, having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
Dependencies are inferred from the claim text.