Glass bubbles of increased collapse strength
Patent 4391646 Issued on July 5, 1983. Estimated Expiration Date: 
February 25, 2002. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
February 25, 2002. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3129086 3230064 3365315 InventorApplicationNo. 06/352164 filed on 02/25/1982US Classes:523/219, Glass void501/33, Beads501/65And boronExaminersPrimary: Poer, JamesAttorney, Agent or FirmInternational ClassesC03C 11/00 (20060101)C04B 14/02 (20060101) C04B 14/24 (20060101) C08K 7/00 (20060101) C08K 7/28 (20060101) AbstractGlass bubbles of increased collapse strength are prepared. The bubbles have an average particle density of 0.4 or more and are made of glass that consists essentially of SiO2 (60-90 weight-percent), alkali metal oxide (2-20 weight-percent), B2 O3 (1-30 weight-percent), sulfur (0.005 to 0.5 weight-percent), and other conventional glass-forming ingredients.Other References
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