text: the pressure - sensitive adhesive tape of the invention comprises at least two non - adhesive layers forming the tape backing , namely a thermoplastic polymer film layer and a fibrous web layer . the preferred thermoplastic polymer film layer is a polyolefin film or coextruded film with a polypropylene film or film layer being particularly desirable . a first face of the polypropylene film layer is coated with a pressure - sensitive adhesive and generally the opposite face of the film layer is provided with a fibrous web layer . the fibrous web layer can be a thermoplastic fibrous web such as a nonwoven web , knitted web , stitch - bonded web , or a woven web or the like . the fibers forming the fibrous web generally are thermoplastic materials such as a polyolefins or polyesters , with polyesters generally being preferred . the fibrous web is then laminated or extrusion coated with the thermoplastic polymer film layer , preferably a polypropylene film . the film layer prevents the pressure - sensitive adhesive from blocking the tape by flowing through the open nonwoven fibrous structure . generally , a polypropylene film layer is a polypropylene homopolymer , copolymer or blend such as with ethylene , or polyethylene or other alpha - olefin alkyl - monomers and polymers . the pressure - sensitive adhesive is a tackified elastomer where the elastomer is an a - b type block copolymer , wherein the a blocks and b blocks are configured in linear , radial or star configurations . the a block is a mono - alkenyl - arene , preferably polystyrene having a molecular weight between 4000 and 50 , 000 , preferably between 7000 and 30 , 000 . the a block content is preferably about 10 to 50 percent , preferably about 10 to 30 percent of the block copolymer . other suitable a blocks may be formed from alpha - methylstyrene , t - butyl - styrene and other ring alkylated styrenes , as well as mixtures thereof . the b block is an elastomeric conjugated diene , generally polyisoprene having an average molecular weight from about 5000 to about 500 , 000 , preferably from about 50 , 000 to about 200 , 000 . the tackifying components for the elastomer - based adhesives generally comprise solid tackifying resin and / or a liquid tackifier or plasticizer . preferably , the tackifying resins are selected from the group of resins at least partially compatible with the polyisoprene or diene b block portion of the elastomer . although not preferred , generally a relatively minor amount of the tackifying resin can include resins compatible with the a block , which when present are generally termed end block reinforcing resins . generally , end block resins are formed from aromatic monomer species . suitable liquid tackifiers or plasticizers for use in the fastening tape tab adhesive composition include napthenic oils , paraffin oils , aromatic oils , mineral oils or low molecular weight rosin esters , polyterpenes and c - 5 resins . the tackifier portion of the pressure - sensitive adhesive generally comprises from 20 to 300 parts per 100 parts of the elastomeric phase . preferably , this is predominately solid tackifier , however , from 0 to 25 weight percent , preferably 0 to 10 weight percent of the adhesive can be liquid tackifier and / or plasticizer . a roll of warp knit , weft inserted texturized polyester fibrous loop fabric ( millilock ™ style no . 924107 - 640 available from milliken co .) was extrusion coated on the side opposite the side with upstanding fiber loops with an approximate 2 . 0 mil ( 50 microns ) film layer of polypropylene resin . the polypropylene resin used was a tenite ™ p9 - 015 type resin with an antioxidant combination of irganox ™ 1010 , irgafos ™ 168 , a thioester , and hydrotalcite ( experimental resin # x22807 - 37 - 3 from eastman chemical co . ; now available from huntsman chemical as # p9 - 026 ). a release coating ( a 5 % solution of polyvinyl n - octadecyl carbamate prepared as described in u . s . pat . no . 2 , 532 , 011 ) was then coated onto the fibrous loop side of the polypropylene backed fibrous loop material . the excess solvent was dried in a forced air oven at approximately 170 ° f . ( 77 ° c .) to provide a dried release coating on the loops . a pressure - sensitive adhesive was then hot melt coated onto the polypropylene film layer . the adhesive composition used was 77 parts of kraton ™ 1111 styrene - isoprene type block copolymer resin , 23 parts shellflex ™ 371 oil liquid tackifying resin , 92 parts wingtack ™ plus solid tackifying resin , 1 part irganox ™ 1010 antioxidant , and 1 part irganox ™ 565 antioxidant . the adhesive coating thickness was 50 microns . sheet samples of the adhesive coated fibrous loop material ( loop tape ) were aged for 12 days at room temperature , 120 ° f . ( 48 ° c . ), and 140 ° f . ( 60 ° c .) and then were visually inspected for any discoloration or yellowing . none of the samples had yellowed . all of the samples remained white . however , on natural aging over an approximate three month time period , a hint of yellow color was observed to appear on the edge of the loop tape ( in roll form ). a roll of loop tape was prepared as described in example 1 except that 2 parts of irganox ™ 1076 antioxidant was added to the adhesive instead of the irganox ™ 1010 / irganox ™ 565 combination . samples of the loop tape were aged as described in example 1 and then were visually inspected for any discoloration or yellowing . the samples that were aged at room temperature remained white ; however , the samples that were heat aged at 120 ° f . ( 48 ° c .) and 140 ° f . ( 60 ° c .) had yellowed . a roll of loop tape was prepared as described in example 1 except that the thermoplastic polymer resin used was experimental resin # x22807 - 37 - 1 available from eastman chemical co . now huntsman chemical ( zinc oxide used instead of hydrotalcite ). samples of the loop tape were aged as described in example 1 and then were visually inspected for any discoloration or yellowing . none of the samples had yellowed . all of the samples remained white . however , on natural aging over an approximate three month time period , a hint of yellow color was observed to appear on the edge of the loop tape ( in roll form ). a roll of loop tape was prepared as described in example 2 except that 2 parts of irganox ™ 1076 antioxidant was added to the adhesive instead of the irganox ™ 1010 / irganox ™ 565 combination . samples of the loop tape were aged as described in example 1 and then were visually inspected for any discoloration or yellowing . all of the samples had yellowed . a roll of loop tape was prepared as described in example 1 except that tenite ™ p9 - 01 5 polypropylene resin was used . samples of the loop tape were aged as described in example 1 and then were visually inspected for any discoloration or yellowing . all of the samples had yellowed to some extent . these examples were prepared to evaluate adhesives prepared with a different styrene - isoprene type block copolymer elastomer . these examples examine the effect that various antioxidant combinations in the adhesive had on the discoloration of the loop tape . the adhesives compositions outlined in table i below were hot melt coated onto a polypropylene backed fibrous loop material that had been prepared as described in example 1 . table i__________________________________________________________________________exampleelastomer ( parts ) solid tackifying resin ( parts ) antioxidant ( parts . sup . 1 ) __________________________________________________________________________3 100 wingtack ™ 95 ( 80 ) irganox ™ 565 ( 0 . 1 ) irganox ™ 1010 ( 0 . 1 ) 4 100 wingtack ™ 95 ( 80 ) irganox ™ 565 ( 0 . 1 ) polygard ™ hr ( 0 . 3 ) 5 100 wingtack ™ 95 ( 80 ) irganox ™ hr ( 0 . 1 ) polygard ™ hr ( 0 . 3 ) naugard ™ 445 ( 0 . 3 ) __________________________________________________________________________ . sup . 1 parts per 100 parts elastomer the adhesive coating thickness for all loop tape samples was 38 microns . sheet samples of the loop tapes were aged at room temperature for 15 days and were also heat aged for 15 days at 140 ° f . ( 60 ° c .). the samples were then evaluated for yellowing by measuring lab values ( e . g ., tappi test procedure # t - 524 ). the lab values were measured using a labscan ™ spectro colorimeter ( hunter associates laboratory , inc . ; reston , va .). room temperature aged data is summarized in table ii and heat aged data is summarized in table iii . the lab values were measured at the center of the sheet and also along an edge of the sheet . table ii______________________________________ l average a average b averageexample ( edge ; center ) ( edge ; center ) ( edge ; center ) ______________________________________3 94 . 01 ; 94 . 05 - 1 . 23 ; - 1 . 29 2 . 21 ; 2 . 314 93 . 94 ; 93 . 97 - 1 . 28 ; - 1 . 24 2 . 15 ; 2 . 035 93 . 99 ; 94 . 06 - 1 . 31 ; - 1 . 33 2 . 20 ; 2 . 27______________________________________ table iii______________________________________ l average a average b averageexample ( edge ; center ) ( edge ; center ) ( edge ; center ) ______________________________________3 93 . 65 ; 93 . 685 - 1 . 38 ; - 1 . 39 2 . 82 ; 2 . 814 93 . 68 ; 93 . 43 - 1 . 21 ; - 1 . 38 2 . 34 ; 3 . 235 93 . 69 ; 93 . 82 - 1 . 32 ; - 1 . 31 2 . 55 ; 2 . 57______________________________________ the l value is a measure of whiteness . the higher the l value , the more white the sample . the a value is a measure of green to red , with a negative number indicating green and a positive red . the b value is a measure of blue to yellow , with a negative number indicating blue and a positive number indicating yellow . the more positive the b value , the more yellow the sample . the samples were essentially white with very little yellow component . these examples were prepared to examine the effect of varying the amount of antioxidant added to the hot melt pressure - sensitive adhesive formulations . the adhesives outlined in table iv below were each hot melt coated onto a polypropylene backed loop material that had been prepared as described in example 1 except that the polypropylene resin used was the tenite ™ p9 - 015 polypropylene resin . the adhesive coating thickness was 50 microns . table iv__________________________________________________________________________elastomer solid tackifying resin liquid tackifying resinexample ( parts ) ( parts ) ( parts ) antioxidant__________________________________________________________________________ ( parts . sup . 1 ) c4 kraton ™ 1111 ( 77 ) wingtack ™ plus ( 92 ) shellflex ™ 371 ( 23 ) irganox ™ 1010 ( 1 ) + irganox ™ 565 ( 1 ) 6 kraton ™ 1111 ( 77 ) wingtack ™ plus ( 92 ) shellflex ™ 371 ( 23 ) irganox ™ 1010 + irganox ™ 565 ( 0 . 5 ) 7 kraton ™ 1111 ( 77 ) wingtack ™ plus ( 92 ) shellflex ™ 371 ( 23 ) irganox ™ 1010 ( 0 . 25 ) + irganox ™ 565 ( 0 . 25 ) 8 kraton ™ 1111 ( 77 ) wingtack ™ plus ( 92 ) shellflex ™ 371 ( 23 ) irganox ™ 1010 ( 0 . 125 ) + irganox ™ 565__________________________________________________________________________ ( 0 . 125 ) . sup . 1 parts per 100 parts elastomer the loop tape samples were visually examined for color variation immediately and after approximately three months natural aging . a decrease in the amount of yellowing was observed in going from the higher to the lower amounts of antioxidant . a roll of warp knit , weft inserted texturized polyester fibrous loop fabric ( millilock ™ style no . 924107 - 640 available from milliken co .) was extrusion coated on the side opposite the side with the upstanding fiber loops with an approximate 2 . 00 mil ( 50 microns ) film layer of polypropylene resin . the polypropylene resin used was # src - 7 - 558 available from shell chemical co . the resin had an antioxidant combination of irganox ™ 1010 , ultranox ™ 626 , and hydrotalcite . a release coating was then coated onto the fibrous loop side of the polypropylene backed fibrous loop material . the release agent used was an organopolysiloxane - polyurea block copolymer that was prepared by the condensation reaction of an organopolysiloxane diamine with a diisocyanate and a diamine chain extender as described in u . s . pat . nos . 5 , 214 , 119 and 5 , 290 , 615 . the release agent was coated as a 5 % solution in isopropyl alcohol and was oven dried . a pressure - sensitive adhesive was then hot melt coated onto the polypropylene film layer . the adhesive composition used was 100 pads of a styrene - isoprene type block copolymer resin , 100 parts wingtack ™ plus solid tackifying resin , 0 . 12 parts irganox ™ 1010 antioxidant , and 0 . 12 parts irganox ™ 565 antioxidant . the adhesive coating thickness was 38 microns . the loop tape was then evaluated for yellowing by measuring lab values as described for examples 3 - 5 . the lab values were l = 94 . 03 , a =- 1 . 08 , and b = 2 . 02 . tenite ™ p9 - 015 is a polypropylene resin having a mfi of 75 available from eastman chemical co . kraton ™ 41111 is a polystyrene - polyisoprene type linear block copolymer available from shell chemical co . having approximately 15 % s - i diblock , 85 % s - i - s triblock , and a styrene content of about 21 %. kraton ™ 1119 is a polystyrene - polyisoprene type linear block copolymer available from shell chemical co . having approximately 65 % s - i diblock , 35 % s - i - s triblock , and a styrene content of about 22 %. wingtack ™ plus is a solid c5 tackifying resin with a tg of 315 ° kelvin and is available from goodyear chemical co . wingtack ™ 95 is a solid c5 tackifying resin with a tg of 323 ° kelvin and is available from goodyear chemical co . shellflex ™ 371 is a napthenic oil having a tg of 209 ° kelvin and is available from shell chemical co . irganox ™ 1076 is a hindered phenol antioxidant ( cas name : benzenepropanoic acid , 3 , 5 - bis ( 1 , 1 - dimethylethyl )- 4 - hydroxy -, octadecyl ester ) available from ciba - geigy . irganox ™ 1010 is a hindered phenol antioxidant ( cas name : benzenepropanoic acid , 3 , 5 - bis ( 1 , 1 - dimethylethyl )- 4 - hydroxy -, 2 , 2 - bis [[ 3 -[ 3 , 5 - bis ( 1 , 1 - dimethylethyl )- 4 - hydroxyphenyl ]- 1 - oxopropoxy ] methyl ]- 1 , 3 - propanediyl ester ) available from ciba - geigy . irganox ™ 565 is a hindered phenol antioxidant ( cas name : phenol , 4 -[[ 4 , 6 - bis ( octylthio )- 1 , 3 , 5 - triazine - 2 - yl ] amino ]- 2 , 6 - bis ( 1 , 1 - dimethylethyl )-) available from ciba - geigy . irgafos ™ 168 is a phosphite antioxidant ( cas name : phenol , 2 , 4 - bis ( 1 , 1 - dimethylethyl )-, phosphite { 3 : 1 }) available from ciba - geigy . polygard ™ hr is a phosphite antioxidant ( tris ( nonylphenyl ) phosphite ) available from uniroyal . naugard ™ 445 is a phosphite antioxidant ( tris ( nonylphenyl ) phosphite ) available from uniroyal . ultranox ™ 626 is a phosphite antioxidant ( bis ( 2 , 4 - di - t - butyl ) pentaerythritol diphosphite ) available from borg - warner .