Water soluble fibers with post process modifications and articles containing same

Abstract

A fiber having a surface region and an interior region includes a polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety, the fiber having a transverse cross-section including the interior region comprising the polymer having a first degree of hydrolysis and the surface region comprising the polymer having a second degree of hydrolysis greater than the first degree of hydrolysis.

1 . A fiber having a surface region and an interior region, the fiber comprising:
 a polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety, the fiber having a transverse cross-section including the interior region comprising the polymer having a first degree of hydrolysis and the surface region comprising the polymer having a second degree of hydrolysis greater than the first degree of hydrolysis.   
     
     
         2 . The fiber according to  claim 1 , wherein the transverse cross-section of the fiber has an increasing gradient in a degree of hydrolysis of the polymer from the interior region to the surface region. 
     
     
         3 . The fiber according to  claim 1 , wherein the polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety comprises a polyvinyl alcohol homopolymer, a polyvinyl acetate homopolymer, a polyvinyl alcohol copolymer, or combinations thereof. 
     
     
         4 . The fiber according to  claim 3 , wherein the polyvinyl alcohol copolymer is a copolymer of vinyl acetate and vinyl alcohol. 
     
     
         5 . The fiber according to  claim 3 , wherein the polyvinyl alcohol copolymer comprises an anionically modified copolymer. 
     
     
         6 . The fiber according to  claim 5 , wherein the anionically modified copolymer comprises a carboxylate, a sulfonate, or combinations thereof. 
     
     
         7 . The fiber according to  claim 1 , further comprising an additional polymer. 
     
     
         8 . The fiber according to  claim 7 , wherein the additional polymer is selected from the group consisting of: polyvinyl alcohol, polyvinyl acetate, polyacrylate, water-soluble acrylate copolymer, polyvinyl pyrrolidone, polyethylenimine, pullulan, guar gum, gum Acacia, xanthan gum, carrageenan, starch, modified starch, polyalkylene oxide, polyacrylamide, polyacrylic acid, cellulose, cellulose ether, cellulose ester, cellulose amide, polycarboxylic acid, polyaminoacid, polyamide, gelatin, dextrin, copolymers of the foregoing, and combinations of any of the foregoing additional polymers or copolymers. 
     
     
         9 . The fiber according to  claim 1 , wherein the first degree of hydrolysis is in a range from about 79% to about 96% and the second degree of hydrolysis is in a range of from about 88% to 100%. 
     
     
         10 . The fiber according to  claim 1 , wherein the first degree of hydrolysis is in a range from about 79% to about 92% and the second degree of hydrolysis is in a range of from about 88% to about 96%. 
     
     
         11 . The fiber according to  claim 1 , wherein the fiber has a dissolution time of less than 200 seconds in water at about 23° C. 
     
     
         12 . The fiber according to  claim 1 , wherein the fiber has a shrinkage along a longitudinal axis of the fiber in a range of from about 20% to about 70% while contacting water at a temperature in a range of from about 10° C. to about 23° C. 
     
     
         13 . The fiber according to  claim 1 , wherein the polymer in the interior region has a glass transition temperature (T g ) in a range of from about 72° C. to about 72.9° C., and the polymer in the surface region has a T g  in a range of from about 73° C. to about 85° C. 
     
     
         14 . A fiber having a longitudinal axis and a transverse cross-section perpendicular to the longitudinal axis of the fiber, the fiber further having a core and sheath structure along at least a portion of the longitudinal axis, the fiber comprising:
 a core region of the core and sheath structure comprising a polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety having a first degree of hydrolysis less than 100%; and   a sheath region of the core and sheath structure disposed radially outward from the core region in the transverse cross-section, the sheath region comprising the polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety having a second degree of hydrolysis greater than the first degree of hydrolysis.   
     
     
         15 . The fiber according to  claim 14 , wherein the polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety comprises a polyvinyl alcohol homopolymer, a polyvinyl acetate homopolymer, a vinyl acetate and vinyl alcohol copolymer, a modified polyvinyl alcohol copolymer, or combinations thereof. 
     
     
         16 . The fiber according to  claim 14 , wherein a difference between the first degree of hydrolysis and the second degree of hydrolysis is at least 1%. 
     
     
         17 . The fiber according to  claim 14 , wherein a difference between the first degree of hydrolysis and the second degree of hydrolysis is in a range of about 1% to about 29%. 
     
     
         18 . The fiber according to  claim 14 , wherein the polymer in the core region has a first degree of polymerization and the polymer in the sheath region has a second degree of polymerization equal to the first degree of polymerization. 
     
     
         19 . The fiber according to  claim 14 , further comprising an intermediate region disposed between the core region and the sheath region in the transverse cross-section, the intermediate region comprising the polymer having a third degree of polymerization equal to the first degree of polymerization and the second degree of polymerization. 
     
     
         20 . The fiber according to  claim 14 , further comprising an intermediate region disposed between the core region and the sheath region in the transverse cross-section, the intermediate region comprising the polymer having a third degree of hydrolysis greater than the first degree of hydrolysis and less than the second degree of hydrolysis. 
     
     
         21 . The fiber according to  claim 14 , further comprising an intermediate region disposed between the core region and the sheath region in the transverse cross-section, wherein each of the core region, the sheath region, and the intermediate region comprises a modified polyvinyl alcohol copolymer having a same degree of modification. 
     
     
         22 . The fiber according to  claim 14 , further comprising a plurality of intermediate regions disposed between the core region and the sheath region in the transverse cross-section, wherein the transverse cross section has an increasing gradient in a degree of hydrolysis from a first intermediate region of the plurality of regions disposed adjacent the core region to a second intermediate region of the plurality of regions disposed radially outward from the first intermediate region. 
     
     
         23 . The fiber according to  claim 14 , wherein the sheath region has a second degree of hydrolysis in a range of from about 88% to about 96% and the fiber has a dissolution time of less than 200 seconds in water at about 23° C. 
     
     
         24 . The fiber according to  claim 14 , wherein the sheath region has a second degree of hydrolysis in a range of from about 88% to about 96% and the fiber has a drying shrinkage in a range of from about 20% to about 70% after soaking in water at a temperature in a range of from about 10° C. to about 23° C. 
     
     
         25 . The fiber according to  claim 14 , wherein the sheath region has a second degree of hydrolysis in a range of from about 88% to about 96% and the polymer in the sheath region has a glass transition temperature in a range of from about 73° C. to about 85° C. 
     
     
         26 . A fiber, comprising:
 a first region comprising a polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety having a first degree of hydrolysis less than 100%; and   a second region comprising the polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety having a second degree of hydrolysis greater than the first degree of hydrolysis,   wherein the polymer comprises a polyvinyl alcohol homopolymer, a polyvinyl acetate homopolymer, a vinyl acetate and vinyl alcohol copolymer, a modified polyvinyl alcohol copolymer, or a combination thereof.   
     
     
         27 . The fiber according to  claim 26 , wherein the fiber has a longitudinal axis, the first region forms a core region of the fiber along the longitudinal axis and the second region forms a sheath region of the fiber surrounding at least a portion of the core region. 
     
     
         28 . The fiber according to  claim 27 , wherein the fiber has a transverse cross-section perpendicular to the longitudinal axis, the fiber further comprises an intermediate region disposed between the first region and the second region in the transverse cross-section, the intermediate region comprising the polymer having a third degree of hydrolysis greater than the first degree of hydrolysis and less than the second degree of hydrolysis. 
     
     
         29 . The fiber according to  claim 27 , wherein the fiber has a transverse cross-section perpendicular to the longitudinal axis, the fiber further comprising a plurality of intermediate regions comprising the polymer and disposed between the first region and the second region, and the transverse cross-section has an increasing gradient in a degree of hydrolysis from the first region to the second region. 
     
     
         30 . The fiber according to  claim 26 , wherein a difference between the first degree of hydrolysis and the second degree of hydrolysis is at least 1%. 
     
     
         31 . The fiber according to  claim 26 , wherein a difference between the first degree of hydrolysis and the second degree of hydrolysis is in a range of from about 1% to about 29%. 
     
     
         32 . The fiber according to  claim 26 , wherein the fiber has a transverse cross-section perpendicular to the longitudinal axis, the fiber further comprises an intermediate region comprising the polymer and disposed between the first region and the second region in the transverse cross-section, and the polymer in each of the first region, the second region, and the third region has a same degree of polymerization. 
     
     
         33 . The fiber according to  claim 26 , wherein the fiber has a transverse cross-section perpendicular to the longitudinal axis, the fiber further comprises an intermediate region comprising the polymer and disposed between the first region and the second region in the transverse cross-section, and the polymer in the first region, the second region, and the third region comprises a modified polyvinyl alcohol polymer having a same degree of modification. 
     
     
         34 . A nonwoven web comprising the fiber according to  claim 26 . 
     
     
         35 . A multilayer nonwoven web comprising a first layer comprising the nonwoven web according to  claim 34 . 
     
     
         36 . A pouch comprising the nonwoven web according to  claim 35  in a form of a pouch defining an interior pouch volume. 
     
     
         37 . A sealed article comprising the nonwoven web according to  claim 34 . 
     
     
         38 . A flushable article comprising the nonwoven web according to  claim 34 . 
     
     
         39 . A wearable absorbent article, comprising:
 an absorbent core having a wearer facing side and an outer facing side; and   a liquid acquisition layer, wherein the liquid acquisition layer comprises the nonwoven web according to  claim 34 .   
     
     
         40 . A particle having a core-shell structure, the particle comprising:
 a core region of the core-shell structure comprising a polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety and having a first degree of hydrolysis less than 100%; and   a shell region disposed radially outward from the core region, the shell region comprising the polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety having a second degree of hydrolysis greater than the first degree of hydrolysis.   
     
     
         41 . The particle according to  claim 40 , wherein the particle has an increasing gradient in a degree of hydrolysis of the polymer radially from a center of the core region to an exterior surface of the shell region. 
     
     
         42 . The particle according to  claim 40 , wherein the polymer comprising at least one of a vinyl acetate moiety or a vinyl alcohol moiety comprises a polyvinyl alcohol homopolymer, a polyvinyl acetate homopolymer, a polyvinyl alcohol copolymer, or combinations thereof. 
     
     
         43 . The particle according to  claim 42 , wherein the polyvinyl alcohol copolymer is a copolymer of vinyl acetate and vinyl alcohol. 
     
     
         44 . The particle according to  claim 42 , wherein the polyvinyl alcohol copolymer is anionically modified, and further comprises a carboxylate, a sulfonate, or combinations thereof. 
     
     
         45 . The particle according to  claim 40 , wherein the particle has one of a spherical shape or an irregular shape. 
     
     
         46 . The particle according to  claim 40 , wherein the particle is one of a microsphere or a bead.