Blend of polytetrafluoroethylene, glass and polyphenylene sulfide fibers and filter felt made from same

Abstract

An improved intimate cardable fiber blend containing polytetrafluoroethylene fibers, dual glass fibers and polyphenylene sulfide fibers and a filtration felt including a needled batt of the intimate cardable fiber blend made by mechanically blending the polyphenylene sulfide fibers and glass fibers with polytetrafluoroethylene fibers, carding the blend to form a nonwoven batt and needling the batt to provide a felt.

1 . An intimate blend of fibers comprising polyphenylene sulfide fibers, glass fibers and fluoropolymer fibers.  
   
   
       2 . The blend according to  claim 1  including from about 20% to about 70% glass fibers.  
   
   
       3 . The blend according to  claim 2  including from about 30% to about 50% glass fibers.  
   
   
       4 . The blend according to  claim 3  wherein the glass fibers are dual glass fibers.  
   
   
       5 . The blend according to  claim 3  wherein the glass fibers are between about 1.5 inches and 4 inches in length and have a diameter of about 6 microns.  
   
   
       6 . The blend according to  claim 1  wherein the blend includes from about 40% to about 60% polyphenylene sulfide fibers.  
   
   
       7 . The blend according to  claim 6  wherein the polyphenylene sulfide fibers are between about 2.0 inches and about 4.5 inches in length and have a denier per filament of between about 2 and about 7.  
   
   
       8 . The blend according to  claim 1  including from about 5% to about 30% polytetrafluoroethylene fibers.  
   
   
       9 . The blend according to  claim 8  including from about 7% to about 20% polytetrafluoroethylene fibers.  
   
   
       10 . The blend according to  claim 1  including from about 40% to about 60% polyphenylene sulfide fibers, from about 30% to about 50% glass fibers and about 10% polytetrafluoroethylene fibers.  
   
   
       11 . The blend according to  claim 1  wherein the polyphenylene fibers are present in an amount less than that of the glass fibers.  
   
   
       12 . The blend according to  claim 1  wherein the ratio of glass fibers and polyphenylene fibers to fluoropolymer fibers is about 9 to 1.  
   
   
       13 . The blend according to  claim 1  wherein the ratio of glass fibers and fluoropolymer fibers to polyphenylene fibers is from about 2 to 3 to about 3 to 2.  
   
   
       14 . The blend according to  claim 1  wherein the ratio of fluoropolymer fibers and polyphenylene fibers to glass fibers is from about 1 to 1 to about 7 to 3.  
   
   
       15 . The blend according to  claim 1  wherein for every one part fluoropolymer fibers there is between about 3 to about 5 parts glass fibers and between about 4 to about 6 parts polyphenylene sulfide fibers.  
   
   
       16 . The fiber blend according to  claim 1  comprising about one part polytetrafluoroethylene staple fibers, about 3 to about 5 parts glass staple fibers and about 4 to about 6 parts polyphenylene sulfide staple fibers.  
   
   
       17 . A filter comprising a membrane-type filter laminated to a filter felt prepared from the intimate fiber blend of  claim 1 .  
   
   
       18 . The filter according to  claim 17  wherein the membrane-type filter is a polytetrafluoroethylene membrane.  
   
   
       19 . An improved filter felt comprising a needled batt of the intimate fiber blend of  claim 1 .  
   
   
       20 . The felt according to  claim 19  having a weight ranging between about 14.8 ounces per square yard to about 18.2 ounces per square yard.  
   
   
       21 . The felt according to  claim 19  having a thickness ranging between about 0.074 inches to about 0.088 inches.  
   
   
       22 . The felt according to  claim 19  wherein the supporting scrim is made of at least one of polyphenylene sulfide fibers and polytetrafluoroethylene fibers.  
   
   
       23 . The felt according to  claim 19  wherein the felt exhibits a PM 2.5 emissions result of about 0.0000249 grams per dry standard cubic meter according to ASTM Test Method D6830-02.  
   
   
       24 . The felt according to  claim 19  wherein the felt exhibits a total mass emissions result of about 0.0000249 grams per dry standard cubic meter according to ASTM Test Method D6830-02.  
   
   
       25 . The felt according to  claim 19  wherein the felt exhibits an initial residual pressure drop of about 2.28 centimeters of water gauge according to ASTM Test Method D6830-02.  
   
   
       26 . The felt according to  claim 19  wherein the felt exhibits a residual pressure drop increase of about 1.39 centimeters of water gauge according to ASTM Test Method D6830-02.  
   
   
       27 . The felt according to  claim 19  wherein the felt exhibits an average residual pressure drop of about 3.03 centimeters of water gauge according to ASTM Test Method D6830-02.  
   
   
       28 . The felt according to  claim 19  wherein the felt exhibits a filter sample weight gain of about 1.82 grams according to ASTM Test Method D6830-02.  
   
   
       29 . The felt according to  claim 19  wherein the felt exhibits a PM 2.5 removal efficiency of about 99.99981% according to ASTM Test Method D6830-02.  
   
   
       30 . The felt according to  claim 19  wherein the felt exhibits a total mass removal efficiency of about 99.99985% according to ASTM Test Method D6830-02.  
   
   
       31 . The felt according to  claim 19  wherein the felt exhibits a permeability of about 25.2 cubic feet per minute to about 40.4 cubic feet per minute.  
   
   
       32 . The felt according to  claim 19  wherein the felt exhibits a Mullen Burst strength average of about 252 pounds per square inch to about 298 pounds per square inch.  
   
   
       33 . The felt according to  claim 19  wherein the felt exhibits, according to ASTM Test Method D6830-02, less PM 2.5 emissions than that of a 100% polyphenylene sulfide fiber filter felt material having a weight per square yard substantially equal to the weight per square yard of the felt.  
   
   
       34 . The felt according to  claim 19  wherein the felt exhibits a Mullen Burst strength average greater than that of a 100% polyphenylene sulfide fiber filter felt material having a weight per square yard substantially equal to the weight per square yard of the felt.  
   
   
       35 . The felt according to  claim 19  wherein the felt exhibits a greater resistance to burn-through from a spark than that of a 100% polyphenylene sulfide fiber filter felt material having a weight per square yard substantially equal to the weight per square yard of the felt.  
   
   
       36 . The felt according to  claim 19  wherein the felt exhibits a burn-through temperature greater than that of a 100% polyphenylene sulfide fiber filter felt material having a weight per square yard substantially equal to the weight per square yard of the felt.  
   
   
       37 . A process for preparing the filter felt of  claim 19  comprising, 
 mechanically blending about 3 to about 5 parts glass staple fibers and about 4 to about 6 parts polyphenylene sulfide staple fibers to every one part polytetrafluoroethylene staple fibers,    carding and crosslapping the fibers with a carding machine, and    needling the batt onto one or both sides a scrim of polyphenylene sulfide fibers.    
   
   
       38 . The felt according to  claim 19  wherein the felt resists melt-through by one or more stainless steel ball bearings of ¼ to ½ inch, heated to about 343° C., when the heated one or more ball bearings are placed on the filter felt while the filter is stretched horizontally across a frame.  
   
   
       39 . An intimate fiber blend comprising about one part polytetrafluoroethylene staple fibers, about 3 parts glass staple fibers and about 6 parts polyphenylene sulfide staple fibers wherein the polyphenylene sulfide staple fibers are present as 2.7 denier polyphenylene sulfide staple fibers and the polytetrafluoroethylene staple fibers have a denier per filament of between 3.5 and 6.7.  
   
   
       40 . An intimate fiber blend comprising about one part polytetrafluoroethylene staple fibers, about 4 parts glass staple fibers and about 5 parts polyphenylene sulfide staple fibers wherein the polyphenylene sulfide staple fibers are present as 2.7 denier polyphenylene sulfide staple fibers and the polytetrafluoroethylene staple fibers have a denier per filament of between 3.5 and 6.7.  
   
   
       41 . An intimate fiber blend comprising about one part polytetrafluoroethylene staple fibers, about 5 parts glass staple fibers and about 4 parts polyphenylene sulfide staple fibers wherein the polyphenylene sulfide staple fibers are present as 2.7 denier polyphenylene sulfide staple fibers and the polytetrafluoroethylene staple fibers have a denier per filament of between 3.5 and 6.7.