High performance elastic composite materials made from high molecular weight thermoplastic triblock elastomers

• US 6,323,389 B1
• Filed: 10/02/1998
• Issued: 11/27/2001
• Est. Priority Date: 10/03/1997
• Status: Expired due to Term

• Current Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Original Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Inventors: Willitts, Donald V., Shane, Richard M., Thomas, Oomman P., Fitts, James R. Jr.
• Primary Examiner(s): WEISS, JOHN
• Assistant Examiner(s): Shanoski, Paul
• Application Number:
  US09/165,909
• Time in Patent Office: 1,152 Days
• Field of Search: 604/385.01, 604/370, 604/385.24, 604/385.27, 604/373
• US Class Current: 604/370
• CPC Class Codes: B32B 2038/0028 Stretching, elongating
• CPC Class Codes: B32B 2038/0048 Annealing, relaxing
• CPC Class Codes: B32B 2262/0207 Elastomeric fibres
• CPC Class Codes: B32B 2262/0215 Thermoplastic elastomer fibers
• CPC Class Codes: B32B 2307/51 Elastic
• CPC Class Codes: B32B 2437/00 Clothing anti-ballistic clothing B32B2571/02
• CPC Class Codes: B32B 25/10 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 25/16 comprising polydienes homopolymers or poly-halodienes homopolymers B32B25/12 takes precedence
• CPC Class Codes: B32B 2555/02 Diapers or napkins
• CPC Class Codes: B32B 5/02 characterised by structural features of a fibrous or filamentary layer layer formed of metallic wires B32B15/02; layer formed of natural mineral fibres B32B19/02; layer formed of wood fibres B32B21/02
• CPC Class Codes: B32B 5/022 Non-woven fabric
• CPC Class Codes: B32B 5/26 another layer next to it also being fibrous or filamentary relative arrangement of fibres or filaments of different layers B32B5/12
• CPC Class Codes: D04H 1/4291 Olefin series
• CPC Class Codes: D04H 1/44 the fleeces or layers being consolidated by mechanical means, e.g. by rolling
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: D04H 3/007 Addition polymers
• CPC Class Codes: D04H 3/04 in rectilinear paths, e.g. crossing at right angles

Abstract

The present invention comprises a continuous feed spun bonded laminate having improved elastic properties measured at body temperature. The laminate comprises at least one first and second nonelastic layers between which is sandwiched at least one elastic layer, the elastic layer being comprised of a triblock polystyrene-poly(ethylene/propylene)-polystyrene (“SEPS”) copolymer having a number average molecular weight of about 81,000 g/mol. The weight percent of styrene is approximately 18% and the weight percent of ethylene/propylene is approximately 82%. The molecular weight increase in the EP block, while holding the molecular weight of the styrene block constant, increases the entanglement density, polymer chain persistence length and the relaxation time. The resulting laminate load decay rate and load loss measurements over a period of 12 hours at body temperature showed marked improvement over known CFSBL product. The laminate is particularly useful as side panel material in training pants because of the resistance to sagging at body temperature.

Claims

1. A composite elastic material having improved elastic properties at body temperature, comprising:

A) a first layer of substantially parallel filaments formed of an elastomeric polymer, said polymer having a number average molecular weight of from about 65,000 g/mol to about 100,000 g/mol, wherein said first layer is substantially free of diblock polymer;

B) a second layer of elastomeric meltblown fibers, said meltblown fibers bonded to at least a portion of the first layer filaments;

C) a third layer of spunbond fibers; and

,

D) a fourth layer of spunbond fibers;

wherein said first and second layers are disposed between said third and fourth layers.

2. The composite elastic material of claim 1, wherein said elastomeric polymer of said first layer comprises an A-B-A′

triblock copolymer wherein A and A′

are the same or different thermoplastic polymer, and wherein B is an elastomeric polymer block.

3. The composite elastic material of claim 2, wherein A is a styrene-based polymer.

4. The composite elastic material of claim 2, wherein B is selected from the group consisting of ethylene/propylene and ethylene/butylene.

5. The composite elastic material of claim 4, wherein said ethylene/propylene and ethylene/butylene are saturated.

6. The composite elastic material of claim 4, wherein said ethylene/propylene and ethylene/butylene are unsaturated.

7. The composite elastic material of claim 2, wherein said elastomeric polymer comprises about 18% styrene-based material and about 82% midblock material.

8. The composite elastic material of claim 1, wherein said material has a percent load loss at body temperature over a twelve hour period of less than about 40%.

9. The composite elastic material of claim 1, wherein said material has a percent load loss at body temperature over a twelve hour period of less than about 50%.

10. The composite elastic material of claim 1, wherein said material has a load decay slope at body temperature over a twelve hour period of about −

0.08.

11. The composite elastic material of claim 1, wherein said material has a load decay slope at body temperature over a twelve hour period of about −

0.10.

12. The composite elastic material of claim 1, wherein said elastomeric polymer has a number average molecular weight of from about 65,000 g/mol to about 100,000 g/mol.

13. The composite elastic material of claim 1, wherein said elastomeric polymer has a number average molecular weight of from about 75,000 g/mol to about 90,000 g/mol.

14. The composite elastic material of claim 1, wherein said elastomeric polymer has a number average molecular weight of about 81,000 g/mol.

15. The composite elastic material of claim 1, wherein said meltblown fibers comprise an elastomeric polymer selected from the group consisting of elastic polyesters, elastic polyurethanes, elastic polyamides, elastic copolymers of ethylene and at least one vinyl monomer, and elastic A-B-A′

block copolymers wherein A and A′

are the same or different thermoplastic polymers, and wherein B is an elastomeric polymer block.

16. The composite elastic material of claim 15, wherein said elastomeric polymer is blended with a processing aid.

17. The composite elastic material of claim 15, wherein said elastomeric polymer is blended with a tackifying resin.

18. The composite elastic material of claim 1, further comprising a fifth layer of meltblown material.

19. The composite elastic material of claim 11, wherein said second and said fifth layers of meltblown material are bonded to both sides of said first layer.

20. A training pants article having side panels incorporating a composite elastic material, said elastic material comprising:

A) a first layer of substantially parallel filaments formed of an elastomeric polymer, said polymer having a number average molecular weight of from about 65,000 g/mol to about 100,000 g/mol, wherein said first layer is substantially free of diblock polymer;

B) a second layer of elastomeric meltblown fibers, said meltblown fibers bonded to at least a portion of the first layer filaments so that the elastic fibrous web is anisotropic;

C) a third layer of spunbond fibers; and

,

D) a fourth layer of spunbond fibers;

wherein said first and second layers are disposed between said third and fourth layers.

21. A polymer suitable for use in an elastic material, said polymer comprising an A-B-A′

triblock copolymer wherein A and A′

are the same or different thermoplastic polymer, and wherein B is an elastomeric polymer block, said polymer having a number average molecular weight of from about 65,000 g/mol to about 100,000 glmol;

said A and A′

being a styrene-based polymer and B is selected from the group consisting of ethylene/propylene and ethylene/butylene.

22. The composite elastic material of claim 21, wherein said elastomeric material comprises about 18% A and A′

and about 82% B.