Pavement marking tape comprising acid-resistant microspheres
AssigneeMinnesota Mining and Manufacturing Company
InventorGeoffrey P. Morris
Life of this patent
Estimating the term…
Abstract
An acid-resistant glass article is provided comprising: about 25-45 wt-% SiO.sub.2 ; about 20-35 wt-% TiO.sub.2 ; less than about 5 wt-% B.sub.2 O.sub.3 ; about 15-40 wt-% of an alkaline earth modifier selected from the group consisting of BaO, SrO, and mixtures thereof; and no greater than about 25 wt-% of an alkali-metal oxide selected from the group consisting of Na.sub.2 O, K.sub.2 O, and mixtures thereof. The glass article is preferably in the form of a microsphere that is adapted for use as a retroreflective element in pavement markings.
Claims19
A pavement marking tape comprising a backing and a layer of acid-resistant glass microspheres carried on the backing, said microspheres comprising, on a theoretical oxide basis:
- (a) about 25-45 wt-% SiO.sub.2 ;
- (b) about 20-35 wt-% TiO.sub.2 ;
- (c) less than about 5 wt-% B.sub.2 O.sub.3 ;
- (d) about 15-40 wt-% of an alkaline earth modifier selected from the group consisting of BaO, SrO, and mixtures thereof;
- and
- (e) no greater than about 25 wt-% of an alkali metal oxide selected from the group consisting of Na.sub.2 O, K.sub.2 O, and mixtures thereof;
- wherein the ratio of amount of SiO.sub.2 to the total amount of alkaline earth modifier plus alkali metal oxide is greater than about 0.7.
A pavement marking tape comprising a backing and a layer of acid-resistant glass microspheres carried on the backing, said microspheres comprising, on a theoretical oxide basis:
- (a) about 30-35 wt-% SiO.sub.2 ;
- (b) about 25-35 wt-% TiO.sub.2 ;
- (c) less than about 1 wt-% B.sub.2 O.sub.3 ;
- (d) about 25-35 wt-% of an alkaline earth modifier selected from the group consisting of BaO, SrO, and mixtures thereof;
- and
- (e) about 4-25 wt-% of an alkali-metal oxide selected from the group consisting of Na.sub.2 O, K.sub.2 O, and mixtures thereof;
- wherein the ratio of the amount of SiO.sub.2 to the total amount of alkaline earth modifier plus alkali metal oxide is greater than about 0.7.
A pavement marking tape comprising a backing and a layer of acid-resistant glass microspheres carried on a backing, said microspheres consisting essentially of, on a theoretical oxide basis:
- (a) about 25-45 wt-% SiO.sub.2 ;
- (b) about 20-35 wt-% TiO.sub.2 ;
- (c) less than about 5 wt-% B.sub.2 O.sub.3 ;
- (d) about 20-40 wt-% of an alkaline earth modifier selected from the group consisting of BaO, SrO, and mixtures thereof;
- (e) about 4-25 wt-% of an alkali metal oxide selected from the group consisting of Na.sub.2 O, K.sub.2 O, and mixtures thereof;
- and
- (f) no greater than about 10 wt-% La.sub.2 O.sub.3 ;
- wherein the ratio of the amount of SiO.sub.2 to the total amount of alkaline earth modifier plus alkali metal oxide is greater than about 0.7.
Dependencies are inferred from the claim text.