Fluorescent lamp coating and coating recycling method

Abstract

A process for recovering rare-earth phosphors from an interior of a lamp envelope ( 12 ). The interior of the envelope defines a wall and a base layer ( 14 ) is adhered to the wall. A coating layer ( 16 ) having the rare-earth phosphors is adhered to the base layer. The process includes flowing a gas through the envelope at a rate sufficient to remove particles of the coating layer but not the base layer. The process also includes collecting the particles of the coating layer, the particles containing the rare-earth phosphors. Lamp envelopes ( 12 ) having a base layer ( 14 ) and a phosphor coating layer ( 16 ) suitable for use with the recycling method are also discussed.

What is claimed is:  
     
         1 . A process for recovering rare-earth phosphors from an interior of a lamp envelope, the interior of the envelope comprising a wall, a base layer adhered to the wall, and a coating layer comprising the rare-earth phosphors adhered to the base layer, the process comprising: 
 (A) flowing a gas through the envelope at a rate sufficient to remove particles of the coating layer but not the base layer; and    (B) collecting the particles of the coating layer, the particles containing the rare-earth phosphors.    
     
     
         2 . The process of  claim 1  with the following additional steps subsequent to step (B): 
 (C) flowing another gas through the envelope at a rate sufficient to remove particles of the base layer; and  
 (D) collecting the particles of the base layer.  
 
     
     
         3 . The process of  claim 1  wherein the envelope is glass.  
     
     
         4 . The process of  claim 1  wherein the coating layer is comprised of a system of rare-earth phosphors for use in a fluorescent lamp.  
     
     
         5 . The process of  claim 1  wherein the coating layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic surfacting agent and a thickening agent, wherein the suspension is 0.05 to 0.3 weight percent surfacting agent.  
     
     
         6 . The process of  claim 1  wherein the coating layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic surfacting agent and a thickening agent, wherein the suspension is 1 to 5 weight percent thickening agent.  
     
     
         7 . The process of  claim 1  wherein the coating layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic dispersing agent and a thickening agent, wherein the suspension is 0.1 to 3 weight percent dispersing agent.  
     
     
         8 . The process of  claim 1  wherein the coating layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic dispersing agent and a thickening agent, wherein the suspension is 1 to 5 weight percent thickening agent.  
     
     
         9 . The process of  claim 1  wherein the base layer is comprised of an alumina blend, the alumina blend having gamma alumina with a median particle size in the range of 30 to 100 nm and alpha alumina with a median particle size in the range of 500 to 1500 nm.  
     
     
         10 . The process of  claim 9  wherein the alumina blend is 5 to 80 weight percent gamma alumina and 20 to 95 weight percent alpha alumina.  
     
     
         11 . The process of  claim 1  wherein the base layer is comprised of an alumina blend, the alumina blend is 5 to 80 weight percent gamma alumina and 20 to 95 weight percent alpha alumina.  
     
     
         12 . The process of  claim 1  wherein the base layer is derived from a composition comprising a suspension comprising an alumina blend, a surfacting agent, dispersing agent and thickening agent, wherein the suspension is 0.01 to 5 weight percent surfacting agent.  
     
     
         13 . The process of  claim 1  wherein the base layer is derived from a composition comprising a suspension comprising an alumina blend, a surfacting agent, dispersing agent and thickening agent, wherein the suspension is 0.01 to 5 weight percent dispersing agent.  
     
     
         14 . The process of  claim 1  wherein the base layer is derived from a composition comprising a suspension comprising an alumina blend, a surfacting agent, dispersing agent and thickening agent, wherein the suspension is 0.05 to 20 weight percent thickening agent.  
     
     
         15 . The process of  claim 12 , the alumina blend having gamma alumina with a median particle size in the range of 30 to 100 nm and alpha alumina with a median particle size in the range of 500 to 1500 nm.  
     
     
         16 . The process of  claim 13 , the alumina blend having gamma alumina with a median particle size in the range of 30 to 100 nm and alpha alumina with a median particle size in the range of 500 to 1500 nm.  
     
     
         17 . The process of  claim 14 , the alumina blend having gamma alumina with a median particle size in the range of 30 to 100 nm and alpha alumina with a median particle size in the range of 500 to 1500 nm.  
     
     
         18 . The process of  claim 1  wherein the gas in step (A) is comprised of compressed air.  
     
     
         19 . The process of  claim 2  wherein the gas in step (C) is comprised of compressed air.  
     
     
         20 . The process of  claim 1  wherein during step (A) the gas flows through the envelope at a rate of about 0.2 to about 10 liters per second.  
     
     
         21 . The process of  claim 1  wherein bases are connected to ends of the envelope and the process further comprises the step of removing at least the bases.  
     
     
         22 . The process of  claim 1  wherein the particles of the coating layer are collected using a cyclonic air/particle separator.  
     
     
         23 . The process of  claim 2  wherein the particles of the base layer are collected using a cyclonic air/particle separator.  
     
     
         24 . An envelope for a discharge lamp, the envelope having a light-transmissive substrate having an inner surface comprising: 
 a base layer coated on the inner surface of the envelope, the base layer comprising a blend of alumina particles, the alumina blend having 5 to 80 weight percent gamma alumina with a median particle size in the range of 30 to 100 nm and 20 to 95 weight percent alpha alumina with a median particle size in the range of 500 to 1500 nm, the base layer being applied in a suspension, the suspension containing the alumina particles and surfacting, dispersing and thickening agents, the suspension being 0.01 to 5 weight percent surfacting agent; and    a phosphor layer coated on an inside surface of the base layer, the phosphor layer comprising a rare-earth phosphor system.    
     
     
         25 . The envelope according to  claim 24 , wherein the suspension is 0.05 to 20 weight percent thickening agent.  
     
     
         26 . The envelope according to  claim 24 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic surfacting agent and a thickening agent, wherein the phosphor suspension is 0.05 to 0.3 weight percent surfacting agent.  
     
     
         27 . The envelope according to  claim 24 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic surfacting agent and a thickening agent, wherein the phosphor suspension is 1 to 5 weight percent thickening agent.  
     
     
         28 . The envelope according to  claim 24 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic dispersing agent and a thickening agent, wherein the suspension is 0.1 to 3 weight percent dispersing agent.  
     
     
         29 . The envelope according to  claim 24 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic dispersing agent and a thickening agent, wherein the suspension is 1 to 5 weight percent thickening agent.  
     
     
         30 . An envelope for a discharge lamp, the envelope having a light-transmissive substrate having an inner surface comprising: 
 a base layer coated on the inner surface of the envelope, the base layer comprising a blend of alumina particles, the alumina blend having 5 to 80 weight percent gamma alumina with a median particle size in the range of 30 to 100 nm and 20 to 95 weight percent alpha alumina with a median particle size in the range of 500 to 1500 nm, the base layer being applied in a suspension, the suspension containing the alumina particles and surfacting, dispersing and thickening agents, the suspension being 0.01 to 5 weight percent dispersing agent; and    a phosphor layer coated on an inside surface of the base layer, the phosphor layer comprising a rare-earth phosphor system.    
     
     
         31 . The envelope according to  claim 30 , wherein the suspension is 0.05 to 20 weight percent thickening agent.  
     
     
         32 . The envelope according to  claim 30 , wherein the suspension is 0.05 to 20 weight percent thickening agent.  
     
     
         33 . The envelope according to  claim 30 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic surfacting agent and a thickening agent, wherein the phosphor suspension is 0.05 to 0.3 weight percent surfacting agent.  
     
     
         34 . The envelope according to  claim 30 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic surfacting agent and a thickening agent, wherein the phosphor suspension is 1 to 5 weight percent thickening agent.  
     
     
         35 . The envelope according to  claim 30 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic dispersing agent and a thickening agent, wherein the suspension is 0.1 to 3 weight percent dispersing agent.  
     
     
         36 . The envelope according to  claim 30 , wherein the phosphor layer is derived from a suspension comprising a rare-earth phosphor system, a non-ionic dispersing agent and a thickening agent, wherein the suspension is 1 to 5 weight percent thickening agent.