Stretchable nonwoven fabric and tape
To produce a nonwoven fabric comprising a conjugated fiber comprising a plurality of resins which are different in thermal shrinkage and form a phase separation structure. In the nonwoven fabric, the conjugated fibers are arranged in a direction approximately parallel to a surface direction of the nonwoven fabric and crimped. In addition, the conjugated fibers have an average curvature radius of fiber crimp of 20 to 200 μm and the crimps are distributed approximately uniformly in a thickness direction of the nonwoven fabric. The nonwoven fabric is substantially free from an adhesive agent. In the nonwoven fabric, each fiber is substantially not melt-bonded to another. The conjugated fiber may comprise a polyalkylene arylate-series resin and a modified polyalkylene arylate-series resin and have a side-by-side or eccentric sheath-core form. Since the bimetal form conjugated fibers having specific crimps are appropriately entangled with each other, the nonwoven fabric has a high stretchability and is easily torn by hand, without using scissors. The nonwoven fabric is suitable for a tape such as a bandage or a supporter.
1. A nonwoven fabric comprising a conjugated fiber comprising a plurality of resins which are different in thermal shrinkage and which form a phase separation structure, which plurality of resins comprises polyalkylene arylate resin and a modified polyalkylene arylate resin of said polyalkylene arylate resin, which nonwoven fabric is a tape having a ratio of the strength at break in a length direction relative to the strength at break in a width direction of 1.5 to 50,
wherein the conjugated fibers are arranged in a direction approximately parallel to a surface direction of the nonwoven fabric and crimped and the conjugated fibers have an average curvature radius of fiber crimp of 20 to 200 μm, and the crimps are distributed approximately uniformly in a thickness direction of the nonwoven fabric,
wherein an average fiber length of the conjugated fiber is 10 to 100 mm,
wherein the nonwoven fabric has a curved ratio of fiber of not less than 1.3 and a proportion of the minimum curved ratio of fiber relative to the maximum curved ratio of fiber of not less than 75% in each of three areas, providing that the nonwoven fabric is cut across the thickness direction and the cross section is divided in a direction perpendicular to the thickness direction equally into three, and
wherein the nonwoven fabric is obtained by a process comprising
forming a web with a fiber including said conjugated fiber, and
heating the resulting fiber web with a high-temperature water vapor to allow the conjugated fiber to develop a crimp having an average curvature radius of 20 to 200 μm, wherein the temperature of the high-temperature water vapor is about 70 to 150° C.
2. The nonwoven fabric according to claim 1 , wherein the plurality of resins comprise a non thermal adhesive resin under moisture which has a softening point or melting point of not lower than 100° C. and forms at least a portion of a surface of the conjugated fiber.
3. The nonwoven fabric according to claim 1 , which is substantially free from an adhesive agent, wherein each fiber is substantially not melt-bonded to another.
4. The nonwoven fabric according to claim 1 , wherein the conjugated fiber has a side-by-side or eccentric sheath-core form.
5. The nonwoven fabric according to claim 1 , which further comprises non-conjugated fibers, and wherein a proportion of the conjugated fiber is not less than 80% by mass relative to total amount of the conjugated fiber and the non-conjugated fibers.
6. The nonwoven fabric according to claim 1 , which has a plurality of low-density portions and a plurality of high-density portions in a surface direction, wherein the low-density portion and the high-density portion are alternately formed in a periodic pattern.
7. The nonwoven fabric according to claim 1 , which has a strength at break of 5 to 30 N/50 mm, an elongation at break of not less than 50%, a recovery after 50% elongation of not less than 80%, and a slip stress at curved surfaces in contact of not less than 0.5 N/50 mm, in at least one direction.
8. The nonwoven fabric according to claim 1 , wherein the tape is selected from the group consisting of a bandage and a supporter.
9. The nonwoven fabric according to claim 1 , wherein the curved ratio of fiber is about 1.4 to 4.
10. The nonwoven fabric according to claim 1 , wherein the curved ratio of fiber is about 1.6 to 3.
11. The nonwoven fabric according to claim 1 , wherein the curved ratio of fiber is about 1.8 to 2.5.
12. The nonwoven fabric according to claim 1 , wherein the proportion of the minimum curved ratio of fiber relative to the maximum curved ratio of fiber is about 80 to 99% in each of the three areas.
13. The nonwoven fabric according to claim 1 , wherein the proportion of the minimum curved ratio of fiber relative to the maximum curved ratio of fiber is about 82 to 98% in each of the three areas.
14. The nonwoven fabric according to claim 1 , wherein the proportion of the minimum curved ratio of fiber relative to the maximum curved ratio of fiber is about 85 to 97% in each of the three areas.
15. The nonwoven fabric according to claim 1 , which has a bulk density of about 0.01 to 0.15 g/cm 3 .
16. The nonwoven fabric according to claim 1 , which has a bulk density of about 0.07 to 0.15 g/cm 3 .
17. The nonwoven fabric according to claim 1 , wherein the polyalkylene arylate resin is a homopolymer and the modified polyalkylene arylate resin is a copolymer comprising a copolymerizable component lowering the melting point or softening point, or the degree of crystallization, of the polyalkylene arylate resin.
18. The nonwoven fabric according to claim 17 , wherein the copolymerizable component comprises at least one of an asymmetric aromatic dicarboxylic acid and a polyoxyC 2-4 alkylene glycol.