Plastically deformable nonwoven web
A nonwoven web formed of substantially continuous spunmelt fibers is formed from a homopolymer of polypropylene having a skewed molecular weight distribution and a polydispersity of less than 3.5. The web, when subjected to high speed incremental deformation, is plastically deformed and characterized by, e.g., a tensile strength at 400% elongation which is at least 10% of the peak tensile strength, a tensile strength at 250% elongation which is at least 40% of the peak tensile strength, and a ratio of the viscoelastic deformation energy after the peak tensile strength to the viscoelastic deformation energy before the peak tensile strength which is greater than one.
1 . A nonwoven web formed of substantially continuous spunmelt fibers comprising a homopolymer of polypropylene;
said web, when subjected to high speed incremental deformation, being plastically deformed and, in at least one direction, being characterized by at least one of:
(i) a tensile strength at 400% elongation which is at least 10% of the peak tensile strength,
(ii) a tensile strength at 250% elongation which is at least 40% of the peak tensile strength, and
(iii) a ratio of the viscoelastic deformation energy after the peak tensile strength to the viscoelastic deformation energy before the peak tensile strength which is greater than one.
2 . The web of claim 1 wherein said homopolymer is a physical blend of at least two homopolymers of polypropylene, at least one of said at least two homopolymers having a polydispersity of less than 3.3, and said at least two homopolymers having a substantially different weight average molecular weight, and after blending said at least two homopolymers in combination having a skewed molecular weight distribution and a polydispersity of less than 3.5.
3 . The web of claim 2 wherein said skewed molecular weight distribution is characterized:
(i) below the peak weight average molecular weight, by a gradual slope and a long tail towards the low molecular weights, and
(ii) above the peak weight average molecular weight, by a steep slope and a short tail towards the high molecular weights.
4 . The web of claim 1 wherein said homopolymer is a reaction product having a polydispersity of less than 3.5 and a skewed molecular weight distribution.
5 . The web of claim 4 wherein said skewed molecular weight distribution is characterized:
(i) below the peak weight average molecular weight, by a gradual slope and a long tail towards the low molecular weights, and
(ii) above the peak weight average molecular weight, by a steep slope and a short tail towards the high molecular weights.
6 . The web of claim 1 wherein the high speed incremental deformation is at least 400 mm/minute applied to an original undeformed dimension not greater than 0.5 inch.
7 . The web of claim 1 wherein the high speed incremental deformation occurs at a web temperature of 50-80° C.
8 . The web of claim 1 wherein the high speed incremental deformation occurs at an ambient web temperature.
9 . The web of claim 1 wherein said continuous fibers are spunbond and have a diameter of 10-50 microns.
10 . The web of claim 1 wherein said continuous fibers are meltblown and have a diameter of 0.5-10 microns.
11 . The web of claim 1 which is characterized by at least two of characteristics (i), (ii), and (iii).
12 . The web of claim 1 which is characterized by each of characteristics (i), (ii), and (iii).
13 . The web of claim 1 wherein said continuous fibers of said web are hydroentangled or hydroengorged.
14 . The web of claim 1 wherein said continuous fibers of said web are asymmetrically bonded.
15 . The web of claim 1 wherein said ratio is at least two.
16 . The web of claim 1 wherein said tensile strength at 450% elongation is at least 10% of said peak tensile strength.
17 . The web of claim 1 wherein said tensile strength at 250% elongation is at least 50% of said peak tensile strength.
18 . A nonwoven web formed of substantially continuous spunmelt fibers comprising a homopolymer of polypropylene, said homopolymer being one of
(i) a physical blend of at least two homopolymers of polypropylene, at least one of said at least two homopolymers having a polydispersity of less than 3.3, said at least two homopolymers having a substantially different weight average molecular weight, and after blending said at least two homopolymers in combination having a skewed molecular weight distribution and a polydispersity of less than 3.5; and
(ii) a reaction product having a polydispersity of less than 3.5 and a skewed molecular weight distribution;
said web, when subjected to high speed incremental deformation, is plastically deformed and has a structural extensibility in at least one direction.
19 . The web of claim 18 wherein said skewed molecular weight distribution is characterized:
(i) below the peak weight average molecular weight, by a gradual slope and a long tail towards the low molecular weights, and
(ii) above the peak weight average molecular weight, by a steep slope and a short tail towards the high molecular weights.
20 . The web of claim 18 wherein the high speed incremental deformation is at least 400 mm/minute applied to an original undeformed dimension not greater than 0.5 inch.
21 . The web of claim 18 wherein the high speed incremental deformation occurs at a web temperature of 50-80° C.
22 . The web of claim 18 wherein the high speed incremental deformation occurs at an ambient web temperature.
23 . The web of claim 18 wherein said continuous fibers are spunbond and have a diameter of 10-50 microns.
24 . The web of claim 18 wherein said continuous fibers are meltblown and have a diameter of 0.5-10 microns.
25 . The web of claim 18 wherein said continuous fibers of said web are hydroentangled or hydroengorged.
26 . The web of claim 18 wherein said continuous fibers of said web are asymmetrically bonded.
27 . The web of claim 18 wherein said homopolymer is said physical blend.
28 . The web of claim 18 wherein said homopolymer is said reaction product.
29 . The web of claim 18 wherein said structural extensibility in at least one direction is characterized by at least one of:
(i) a tensile strength at 400% elongation which is at least 10% of the peak tensile strength,
(ii) a tensile strength at 250% elongation which is at least 40% of the peak tensile strength, and
(iii) a ratio of the viscoelastic deformation energy after the peak tensile strength to the viscoelastic deformation energy before the peak tensile strength which is greater than one.
30 . The web of claim 29 which is characterized by at least two of characteristics (i), (ii), and (iii).
31 . The web of claim 29 which is characterized by each of characteristics (i), (ii), and (iii).
32 . The web of claim 29 wherein said ratio is at least two.
33 . The web of claim 29 wherein said tensile strength of 450% elongation is at least 10% of said peak tensile strength.
34 . The web of claim 29 wherein said tensile strength at 250% elongation is at least 50% of said peak tensile strength.
35 . The web of claim 18 wherein said continuous fibers of said web are asymmetrically bonded.
36 . A method of making a nonwoven web formed of substantially continuous spunmelt fibers, comprising the step of:
forming a spunbond nonwoven web comprising essentially of fibers of a homopolymer of polypropylene using:
(i) quench air at 8-20° C.,
(ii) a fiber speed of 500-2,500 meters/minute, and
(iii) a bonding temperature of 75-150° C.;
thereby to form a web which, when subjected to high speed incremental deformation, is plastically deformed and, in at least one direction, is characterized by at least one of:
(i) a tensile strength at 400% elongation which is at least 10% of the peak tensile strength,
(ii) a tensile strength at 250% elongation which is at least 40% of the peak tensile strength, and
(iii) a ratio of the viscoelastic deformation energy after the peak tensile strength to the viscoelastic deformation energy before the peak tensile strength which is greater than one.
37 . The method of claim 36 wherein
(i) the quench air is about 12-14° C.,
(ii) the fiber speed is about 1,000-2,000 meters/minute, and
(iii) the bonding temperature is about 110-125° C.
38 . The method of claim 36 wherein the homopolymer is a physical blend of at least two homopolymers of polypropylene, at least one of the at least two homopolymers having a polydispersity of less than 3.3, and the at least two homopolymers having a substantially different weight average molecular weight, and after blending the at least two homopolymers in combination having a skewed molecular weight distribution and a polydispersity of less than 3.5.
39 . The method of claim 38 wherein the skewed molecular weight distribution is characterized:
(i) below the peak weight average molecular weight, by a gradual slope and a long tail towards the low molecular weights, and
(ii) above the peak weight average molecular weight, by a steep slope and a short tail towards the high molecular weights.
40 . The method of claim 36 wherein the homopolymer is a reaction product having a polydispersity of less than 3.5 and a skewed molecular weight distribution.
41 . The method of claim 40 wherein the skewed molecular weight distribution is characterized:
(i) below the peak weight average molecular weight, by a gradual slope and a long tail towards the low molecular weights, and
(ii) above the peak weight average molecular weight, by a steep slope and a short tail towards the high molecular weights.
42 . The method of claim 36 wherein the high speed incremental deformation is at least 400 mm/minute applied to an original undeformed dimension not greater than 0.5 inch.
43 . The method of claim 36 wherein the high speed incremental deformation occurs at a web temperature of 50-80° C.
44 . The method of claim 36 wherein the high speed incremental deformation occurs at ambient web temperature.
45 . The method of claim 36 wherein the homopolymer exhibits a low elastic resistance during high speed incremental stretching.
46 . The method of claim 36 wherein the fibers of the web have a diameter of 10-50 microns.
47 . The method of claim 36 wherein the web is formed with an asymmetric bonding pattern.
48 . The method of claim 47 wherein the asymmetric bond pattern is a PILLOW BOND pattern.
49 . The method of claim 36 wherein the web is characterized by at least two of (i), (ii), and (iii).
50 . The method of claim 36 wherein the web is characterized by each of (i), (ii), and (iii).
51 . The method of claim 36 wherein the ratio is at least two.
52 . The method of claim 36 wherein the tensile strength of 450% elongation is at least 10% of the peak tensile strength.
53 . The method of claim 36 wherein said tensile strength at 250% elongation is at least 50% of the peak tensile strength.
54 . A bicomponent fiber comprising:
(i) a component of polyethylene or polypropylene polymer, and
(ii) a component of polypropylene homopolymer, said polypropylene homopolymer being one of:
(a) a physical blend of at least two homopolymers of polypropylene, at least one of said at least two homopolymers having a polydispersity of less than 3.3, and said at least two homopolymers having a substantially different weight average molecular weight, and after blending said at least two homopolymers in combination having a skewed molecular weight distribution and a polydispersity of less than 3.5, and
(b) a reaction product having a polydispersity of less than 3.5 and a skewed molecular weight distribution.
55 . The bicomponent fiber of claim 54 wherein said components are in a sheath/core configuration and are substantially similar in shrinkage characteristics as a function of temperature, in plastic deformation characteristics, and in the capacity to bond with other polymeric materials.
56 . The bicomponent fiber of claim 54 wherein said components are in a side-by-side configuration, and are substantially dissimilar in shrinkage characteristics as a function of temperature.
57 . The bicomponent fiber of claim 54 wherein said components are in a pie configuration and are substantially non-adherent to one another.
58 . A multilayer laminate or composite comprising:
(i) the web of claim 1; and
(ii) at least one other web selected from the group consisting of nonwovens, woven textiles, films and combinations thereof.
59 . The composite of claim 58 wherein said at least one other web is a nonwoven.
60 . The composite of claim 58 wherein said at least one other web is a woven textile.
61 . The composite of claim 58 wherein said at least one other web is one of a nonwoven and a breathable film.
62 . The composite of claim 61 wherein said at least one other web is a nonwoven.
63 . The composite of claim 61 wherein said at least one other web is a breathable film.
64 . The composite of claim 58 wherein said at least one other web is one of an elastic nonwoven and an elastic film.
65 . The composite of claim 64 wherein said at least one other web is an elastic nonwoven.
66 . The composite of claim 64 wherein said at least one other web is an elastic film.
67 . The composite of claim 58 wherein said at least one other web is a film of polyethylene homopolymer.
68 . A hydroentangled or hydroengorged spunbond web made of the web of claim 1 .
69 . A hydroentangled or hydroengorged laminate comprising:
(i) two outer spunbond layers made of the web of claim 1 , and
(ii) an intermediate layer therebetween formed at least of wood pulp, cellulosic fibers, viscose fibers or combinations thereof.
70 . A method of forming an apertured web suitable for use as an apertured topsheet, comprising the steps of:
(i) providing the web of claim 1;
(ii) calendering the web to create frangible secondary bonds therein; and
(iii) plastically deforming the calendered web by high speed incremental deformation to create apertures therein.
71 . A method of forming an apertured nonwoven web, comprising the steps of:
(i) providing the nonwoven web of claim 1; and
(ii) creating apertures in the nonwoven web by sucking hot air through a screen supporting the nonwoven web or by hot needling the nonwoven web.
72 . A nonwoven web formed of substantially continuous spunmelt fibers comprising a homopolymer of polypropylene;
said web, when subjected to high speed incremental deformation, being plastically deformed and having a structural extensibility, in at least one direction, characterized by at least one of:
(i) a tensile strength at 400% elongation which is at least 10% of the peak tensile strength,
(ii) a tensile strength at 250% elongation which is at least 40% of the peak tensile strength, and
(iii) a ratio of the viscoelastic deformation energy after the peak tensile strength to the viscoelastic deformation energy before the peak tensile strength which is greater than one.