Low-shrink textile articles made from polypropylene fibers

Abstract

Improved polypropylene fibers exhibiting greatly reduced heat- and moisture-shrink problems are provided. Such fibers require the presence of certain compounds that quickly and effectively provide rigidity to the target polypropylene fiber after heat-setting. Generally, these compounds include any structure that nucleates polymer crystals within the target polypropyelene after exposure to sufficient heat to melt the initial pelletized polymer and upon allowing such a melt to cool. The compounds must nucleate polymer crystals at a higher temperature than the target polypropylene without the nucleating agent during cooling. In such a manner, the “rigidifying” nucleator compounds provide nucleation sites for polypropylene crystal growth. After drawing the nucleated composition into fiber form, the fiber is then exposed to sufficient heat to grow the crystalline network, thus holding the fiber in a desired position. The preferred “rigidifying” compounds include dibenzylidene sorbitol based compounds, as well as less preferred compounds, such as sodium benzoate, certain sodium and lithium phosphate salts (such as sodium 2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate, otherwise known as NA-11). Specific methods of manufacture of such fibers, as well as fabric articles made therefrom, are also encompassed within this invention.

What we claim is:  
     
         1 . A fabric article comprising at least one polypropylene fiber possessing at most 5,000 denier per filament and exhibiting a heat-shrinkage in at least 150° C. hot air of at most 11%, wherein said fiber further comprises at least one nucleating agent.  
     
     
         2 . The fabric article of  claim 1  wherein said article is non-woven.  
     
     
         3 . The fabric article of  claim 1  wherein said article is woven.  
     
     
         4 . The fabric article of  claim 1  wherein said article is knit.  
     
     
         5 . The fabric article of  claim 1  wherein said nucleating agent is selected from the group consisting of p-MDBS, 3,4-DMDBS, 2,4,5-TMDBS, Liquid 3,4-DMDBS, DBS, sodium benzoate, NA-11, NA-21, and any mixtures thereof.  
     
     
         6 . The fabric article of  claim 5  wherein said nucleating agent is p-MDBS.  
     
     
         7 . The fabric article of  claim 1  wherein said at least one polypropylene fiber possesses a denier per filament of at most 1,000, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 9%, and wherein said at least one nucleating agent is present in an amount of at least 100 ppm.  
     
     
         8 . The fabric article of  claim 7  wherein said at least one polypropylene fiber possesses a denier per filament of at most 500, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%, and wherein said at least one nucleating agent is present in an amount of at least 1250 ppm.  
     
     
         9 . The fabric article of  claim 8  wherein said at least one polypropylene fiber possesses a denier per filament of at most 100 and wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%.  
     
     
         10 . A fabric article comprising at least one polypropylene fiber possessing at most 5,000 denier per filament and exhibiting a heat-shrinkage in at least 150° C. hot air of at most 11%, wherein said fiber further exhibits a fiber peak crystallization temperature measurement of at least 115° C. as measured by differential scanning calorimetry in accordance with ASTM Test Method D3417-99 at a cooling rate of 20° C./min.  
     
     
         11 . The fabric article of  claim 10  wherein said article is non-woven.  
     
     
         12 . The fabric article of  claim 10  wherein said article is woven.  
     
     
         13 . The fabric article of  claim 10  wherein said article is knit.  
     
     
         14 . The fabric article of  claim 10  wherein said at least one polypropylene fiber possesses a denier per filament of at most 1,000, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 9%, and wherein said fiber peak crystallization temperature measurement is at least 116° C.  
     
     
         15 . The fabric article of  claim 14  wherein said at least one polypropylene fiber possesses a denier per filament of at most 500, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%, and wherein said fiber peak crystallization temperature measurement is at least 116.5° C.  
     
     
         16 . The fabric article of  claim 15 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 1100 and wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%.  
     
     
         17 . The fabric article of  claim 10  wherein said at least one polypropylene fiber further comprises at least one nucleating agent.  
     
     
         18 . The fabric article of  claim 17  wherein said nucleating agent is selected from the group consisting of p-MDBS, 3,4-DMDBS, 2,4,5-TMDBS, Liquid 3,4-DMDBS, DBS, sodium benzoate, NA-11, NA-21, and any mixtures thereof.  
     
     
         19 . The fabric article of  claim 18  wherein said nucleating agent is p-MDBS.  
     
     
         20 . The fabric article of  claim 17  wherein said at least one nucleating agent is present in an amount of at least 100 ppm.  
     
     
         21 . The fabric article of  claim 20  wherein said at least one nucleating agent is present in an amount of at least 1250 ppm.  
     
     
         22 . A fabric article comprising at least one polypropylene fiber possessing at most 5,000 denier per filament and exhibiting a heat-shrinkage in at least 150° C. hot air of at most 11%, wherein said fiber further comprises at least one nucleating agent, and wherein said fiber further exhibits a long period of at least 20 nm as measured by small-angle x-ray scattering.  
     
     
         23 . The fabric article of  claim 22  wherein said article is non-woven.  
     
     
         24 . The fabric article of  claim 22  wherein said article is woven.  
     
     
         25 . The fabric article of  claim 22  wherein said article is knit.  
     
     
         26 . The fabric article of  claim 22  wherein said nucleating agent is selected from the group consisting of p-MDBS, 3,4-DMDBS, 2,4,5-TMDBS, Liquid 3,4-DMDBS, DBS, sodium benzoate, NA-11, NA-21, and any mixtures thereof.  
     
     
         27 . The fabric article of  claim 23  wherein said nucleating agent is p-MDBS.  
     
     
         28 . The fabric article of 22 wherein said at least one polypropylene fiber possesses a denier per filament of at most 1,000, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 9%, wherein said at least one nucleating agent is present in an amount of at least 100 ppm, and wherein said fiber exhibits a long period of at least 22 nm.  
     
     
         29 . The fabric article of  claim 28  where said at least one polypropylene fiber possesses a denier per filament of at most 500, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%, and wherein said at least one nucleating agent is present in an amount of at least 1250 ppm.  
     
     
         30 . The fabric article of  claim 29 , wherein said at least one propylene fiber possesses a denier per filament of at most 100 and wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%.  
     
     
         31 . A fabric article comprising at least one polypropylene fiber possessing at most 5,000 denier per filament and exhibiting a heat-shrinkage in at least 150° C. hot air of at most 11%, wherein said fiber further exhibits a fiber peak crystallization temperature measurement of at least 115° C. as measured by differential scanning calorimetry in accordance with ASTM Test Method D3417-99 at a cooling rate of 20° C./min, and wherein said fiber further exhibits a long period of at least 20 nm as measured by small-angle x-ray scattering.  
     
     
         32 . The fabric article of  claim 31  wherein said article is non-woven.  
     
     
         33 . The fabric article of  claim 31  wherein said article is woven.  
     
     
         34 . The fabric article of  claim 31  wherein said article is knit.  
     
     
         35 . The fabric article of  claim 31 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 1,000, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 9%, wherein said peak crystallization temperature is at least 116° C., and wherein said fiber exhibits a long period of at least 22 nm.  
     
     
         36 . The fabric article of  claim 35 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 500, wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%, and wherein said peak crystallization temperature is at least 116.5° C.  
     
     
         37 . The fabric article of  claim 36 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 100 and wherein said fiber exhibits a heat shrinkage in at least 150° C. hot air of at most 8%.  
     
     
         38 . The fabric article of  claim 31  wherein said at least one polypropylene fiber further comprises at least one nucleating agent.  
     
     
         39 . The fabric article of  claim 38  wherein said nucleating agent is selected from the group consisting of p-MDBS, 3,4-DMDBS, 2,4,5-TMDBS, Liquid 3,4-DMDBS, DBS, sodium benzoate, NA-11, NA-21, and any mixtures thereof.  
     
     
         40 . The fabric article of  claim 39  wherein said nucleating agent is p-MDBS.  
     
     
         41 . The fabric article of  claim 38  wherein said at least one nucleating agent is present in an amount of at least 100 ppm.  
     
     
         42 . The fabric article of  claim 41  wherein said at least one nucleating agent is present in an amount of at least 1250 ppm.  
     
     
         43 . A fabric article comprising at least one polypropylene fiber possessing at most 5,000 denier per filament and comprising at least one nucleating agent, and wherein said fiber further exhibits a long period of at least 20 nm as measured by small-angle x-ray scattering.  
     
     
         44 . The fabric article of  claim 43  wherein said article is non-woven.  
     
     
         45 . The fabric article of  claim 43  wherein said article is woven.  
     
     
         46 . The fabric article of  claim 43  wherein said article is knit.  
     
     
         47 . The fabric article of  claim 43  wherein said nucleating agent is selected from the group consisting of p-MDBS, 3,4-DMDBS, 2,4,5-TMDBS, Liquid 3,4-DMDBS, DBS, sodium benzoate, NA-11, NA-21, and any mixtures thereof.  
     
     
         48 . The fabric article of  claim 47  wherein said nucleating agent is p-MDBS.  
     
     
         49 . The fabric article of  claim 43  wherein said fiber possesses a denier per filament of at most 1,000, wherein said at least one nucleating agent is present in an amount of at least 1100 ppm, and wherein said fiber exhibits a long period of at least 22 nm.  
     
     
         50 . The fabric article of  claim 49 , wherein said fiber possesses a denier per filament of at most 500, and wherein said at least one nucleating agent is present in an amount of at least 1250 ppm.  
     
     
         51 . The fabric article of  claim 50 , wherein said fiber possesses a denier per filament of at most 100.  
     
     
         52 . A fabric article comprising at least one polypropylene fiber possessing at most 5,000 denier per filament and exhibiting a peak crystallization temperature of at least 115° C. as measured by differential scanning calorimetry in accordance with a modified ASTM Test Method D3417-99 at a cooling rate of 20° C./min, and wherein said fiber further exhibits a long period of at least 20 as measured by small-angle x-ray scattering.  
     
     
         53 . The fabric article of  claim 52  wherein said article is non-woven.  
     
     
         54 . The fabric article of  claim 52  wherein said article is woven.  
     
     
         55 . The fabric article of  claim 52  wherein said article is knit.  
     
     
         56 . The fabric article of  claim 52 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 1,000, wherein said peak crystallization temperature is at least 116° C., and wherein said fiber exhibits a long period of at least 22 nm.  
     
     
         57 . The fabric article of  claim 56 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 500, and wherein said fiber exhibits a peak crystallization temperature of at least 116.5° C.  
     
     
         58 . The fabric article of  claim 57 , wherein said at least one polypropylene fiber possesses a denier per filament of at most 100.  
     
     
         59 . The fabric article of  claim 52 , wherein said at least one propylene fiber further comprises at least one nucleating agent.  
     
     
         60 . The fabric article of  claim 59  wherein said nucleating agent is selected from the group consisting of p-MDBS, 3,4-DMDBS, 2,4,5-TMDBS, Liquid 3,4-DMDBS, DBS, sodium benzoate, NA-11, NA-21, and any mixtures thereof.  
     
     
         61 . The fabric article of  claim 60  wherein said nucleating agent is p-MDBS.  
     
     
         62 . A woven fabric having a length and a width and comprising at least 90% by weight of polypropylene fibers containing a nucleating agent at a concentration of greater than 100 ppm wherein the area shrinkage of said fabric in after five home washings at a temperature of 60° C. and 5 home dryings at a temperature of 75° C. is less than 6%.  
     
     
         63 . The woven fabric of  claim 62  wherein the shrinkage is less than 4%.  
     
     
         64 . A knit fabric having a length and a width and comprising at least 90% by weight of polypropylene fibers comprising polypropylene fibers containing a nucleating agent at a concentration of greater than 100 ppm wherein the area shrinkage after exposure to hot air at 150° C. for five minutes is less than 12%.  
     
     
         65 . A knit fabric having a length and width and comprising at least 90% by weight of polypropylene fibers containing a nucleation agent at a concentration of greater than 100 ppm wherein the area shrinkage after five home washings at a temperature of 60° C. and five home dryings at a temperature of 75° C. is less than 10%.  
     
     
         66 . A molded non-woven fabric comprising at least 90% by weight of Polypropylene fibers wherein said molded non-woven fabric exhibits a shrinkage amount of at most 12% as compared with the same non-woven fabric prior to molding.