Low emission fibrous webs and method of such webs

Abstract

A nonwoven web of polymer fibers bonded with from about 5 to about 30 wt. percent of a cured binder composition, based on the weight of the web or mat. The web is a spunbonded web of polymer, such as polyester, fibers bound with a binder containing one or more formaldehyde fortified polymer resins that normally emit substantial formaldehyde at high temperatures, but in this invention the binder also contains up to about 7.5 wt. percent of a bisulphite compound, preferably ammonium bisulphite. This binder is applied in latex form to the fibrous web after the fibers are made and collected in a known manner and then the wet web is dried and heated to cure the binder in a known manner. The resultant nonwoven webs have good hot strength and low formaldehyde emissions and reasonable costs, something not heretofore attainable with these types of formaldehyde containing binders. The webs of the present invention are useful for making various roofing products such as built up roofing products and for other uses.

1 . A web of polymer fibers bound by about 5-30 wt. percent, based on the dry weight of the mat, of a formaldehyde containing polymer resin latex binder providing good hot strength at 200 degrees C. and good elasticity to the web, the resin containing at least about 0.75 wt. percent and up to about 7.5 wt. percent of a bisulfite compound, based on the dry weight of the formaldehyde containing resin in the binder.  
     
     
         2 . The web of  claim 1  wherein the resin is selected from the group consisting of formaldehyde fortified latex polymers which may be composed of ethylene-vinyl acetate copolymer, styrene-acrylic copolymer, vinyl-acrylic copolymer, styrene-butadiene-acrylonitrile copolymer, or acrylic copolymer.  
     
     
         3 . The web of  claim 2  wherein the bisulfite is ammonium bisulfite.  
     
     
         4 . The web of  claim 3  wherein the bisulfite is ammonium bisulfite.  
     
     
         5 . The web of  claim 1  wherein the bisulfite compound is present in an amount of at least 1.25 wt. percent.  
     
     
         6 . The web of  claim 2  wherein the bisulfite compound is present in an amount of at least 1.25 wt. percent.  
     
     
         7 . The web of  claim 3  wherein the bisulfite compound is present in an amount of at least 1.25 wt. percent.  
     
     
         8 . The web of  claim 1  wherein the bisulfite compound is present in an amount of at least 2.5 wt. percent.  
     
     
         9 . The web of  claim 2  wherein the bisulfite compound is present in an amount of at least 2.5 wt. percent.  
     
     
         10 . The web of  claim 3  wherein the bisulfite compound is present in an amount of at least 2.5 wt. percent.  
     
     
         11 . The web of  claim 8  wherein the polymer fibers are polyester, the ammonium bisulfite compound is ammonium bisulfite, the binder content of the web is in the range of about 16-24 wt. percent and the basis weight of the web is in the range of about 150-200 gms/sq. meter.  
     
     
         12 . The web of  claim 9  wherein the polymer fibers are polyester, the ammonium bisulfite compound is ammonium bisulfite, the binder content of the web is in the range of about 16-24 wt. percent and the basis weight of the web in the range of about 150-200 gms/sq. meter.  
     
     
         13 . The web of  claim 10  wherein the polymer fibers are polyester, the ammonium bisulfite compound is ammonium bisulfite, the binder content of the web is in the range of about 16-24 wt. percent and the basis weight of the web is in the range of about 150-200 gms/sq. meter.  
     
     
         14 . A method of making a polymer fiber web by melting a polymer, converting the melt to fibers, attenuating the fibers to the desired fiber diameter, collecting the fibers in a random pattern on a collecting surface, applying a latex formaldehyde containing polymer resin binder to the web in an amount that the binder content of the dry web will be in the range of about 5-30 wt. percent, based on the weight of the dry web, and drying the web and curing the polymer resin binder to bond the polymer fibers together to form a nonwoven polymer fiber web, said polymer resin being selected from the group consisting of formaldehyde fortified latex polymers which may be composed of ethylene-vinyl acetate copolymer, styrene-acrylic copolymer, vinyl-acrylic copolymer, styrene-butadiene-acrylonitrile copolymer, or acrylic copolymer, the improvement comprising adding about 0.75-7.5 wt. percent, based on the dry weight of the formaldehyde containing resin, of a bisulfite compound to the latex binder before applying the latex binder to the collected polymer fibers.  
     
     
         15 . The method of  claim 14  wherein about 1.25-7.5 wt. percent of the bisulfite compound is added to the latex binder before applying the latex binder to the collected polymer fibers.  
     
     
         16 . The method of  claim 14  wherein about 2.5-5 wt. percent of the bisulfite compound is added to the latex binder before applying the latex binder to the collected polymer fibers.  
     
     
         17 . The method of  claim 14  wherein the polymer is polyester and the bisulfite compound is ammonium bisulfite.  
     
     
         18 . The method of  claim 15  wherein the polymer is polyester and the bisulfite compound is ammonium bisulfite.  
     
     
         19 . The method of  claim 16  wherein the polymer is polyester and the bisulfite compound is ammonium bisulfite.