Propylene polymers for fibers and fabrics

Details Propylene polymers for fibers and fabrics Propylene polymers for fibers and fabrics

1998-09-29

2002-09-03

Wilson, Donald R. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S065000, C526S160000, C526S348600, C526S943000, C442S401000, C442S407000, C525S240000

Reexamination Certificate

active

06444774

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to fibers and fabrics prepared from crystalline propylene polymer compositions comprising both propylene homopolymer and propylene copolymer components. Preferably the propylene polymer composition is isotactic. The compositions are prepared using metallocene catalyst systems in a polymerization process that involves the sequential or parallel polymerization of propylene homopolymer and copolymer using propylene with a small amount of comonomer, preferably ethylene. The resulting polymer compositions are excellent for use in the production of fibers and fabrics. Fibers prepared with these propylene polymers are substantially more elastic, and fabrics prepared with these polymers are stronger, softer have a higher elongation and have a significantly broader and lower bonding window at lower temperatures compared to fibers and fabrics prepared from known propylene-based polymers. The broader bonding window is especially advantageous when bonding heavy basis weight fabrics.
BACKGROUND
Propylene polymer fibers and fabrics are widely used in many applications including twine, carpet, medical gowns and drapes, and diapers. The optimization of processing characteristics and properties of propylene based fibers and fabrics has been the subject of intense effort. For example, WO 94/28219 and U.S. Pat. No. 5,637,666 describe fibers and fabrics prepared from metallocene catalyzed isotactic polypropylene. These fibers are significantly stronger compared to fibers prepared with Ziegler-Natta catalyzed isotactic polypropylene.
The present inventors have discovered that crystalline propylene polymer compositions made by polymerizing propylene in one stage and then propylene and a minor amount of comonomer in a separate stage using a metallocene catalyst system results in polymers which impart improved elasticity, strength, and processing characteristics when used to make fibers and fabrics.
Multiple stage polymerization processes are known in the art and are usually used to prepare block copolymers which contain rubbery materials as opposed to the crystalline polymers of this invention. U.S. Pat. Nos. 5,280,074; 5,322,902, and 5,346,925, for example, describe two-stage processes for producing propylene block copolymers. The propylene/ethylene copolymer portion of these compositions is a non-crystalline, rubbery material suitable for molding applications rather than fibers and fabrics.
SUMMARY
This invention is directed toward a fiber comprising a crystalline propylene polymer composition comprising: a) from about 10 to about 90 weight percent crystalline, isotactic propylene homopolymer having a molecular weight distribution of less than about 3; and b) from about 90 to about 10 weight percent crystalline propylene copolymer having a molecular weight distribution of less than about 3, wherein the weight percent of the comonomer based on the total weight of the polymer is in the range of from about 0.05 to about 15.
This invention is also directed toward a fabric comprising a crystalline propylene polymer composition comprising: a) from about 10 to about 90 weight percent crystalline, isotactic propylene homopolymer having a molecular weight distribution of less than about 3; and b) from about 90 to about 10 weight percent crystalline propylene copolymer having a molecular weight distribution of less than about 3, wherein the weight percent of the comonomer based on the total weight of the polymer is in the range of from about 0.05 to about 15.
DETAILED DESCRIPTION
As used herein “crystalline” is defined as having one or more identifiable peak melting points above about 100° C. as determined by Differential Scanning Calorimetry (DSC peak melting temperatures).
As used herein, “isotactic” is defined as having at least 40% isotactic pentads according to analysis by
13
C-NMR. As used herein, “highly isotactic” is defined as having at least 60% isotactic pentads according to analysis by
13
C-NMR.
As used herein, “molecular weight” means weight average molecular weight (Mw) and “molecular weight distribution,” (MWD), means Mw divided by number average molecular weight (Mn).
As used herein, unless differentiated, “polymerization” includes copolymerization and terpolymerization, “monomer” includes comonomer and termonomer, and “polymer” includes copolymer and terpolymer.
As used herein the term “fabric” includes woven fabrics, nonwoven fabrics, such as spunbond and meltblown fabrics, composite fabrics and fabric laminates.
Methods for Making Crystalline Propylene Polymer Compositions
The methods of this invention involve the use of metallocene catalyst systems that comprise at least one metallocene and at least one activator. Preferably, these catalyst system components are supported on a support material.
Metallocenes
As used herein “metallocene” refers generally to compounds represented by the formula Cp
m
MR
n
X
q
wherein Cp is a cyclopentadienyl ring which may be substituted, or derivative thereof which may be substituted, M is a Group 4, 5, or 6 transition metal, for example titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten, R is a hydrocarbyl group or hydrocarboxy group having from one to 20 carbon atoms, X is a halogen, and m=1-3, n=0-3, q=0-3, and the sum of m+n+q is equal to the oxidation state of the transition metal.
Methods for making and using metallocenes are very well known in the art. For example, metallocenes are detailed in U.S. Pat. Nos. 4,530,914; 4,542,199; 4,769,910; 4,808,561; 4,871,705; 4,933,403; 4,937,299; 5,017,714; 5,026,798; 5,057,475; 5,120,867; 5,278,119; 5,304,614; 5,324,800; 5,350,723; and 5,391,790 each fully incorporated herein by reference.
Preferred metallocenes are those represented by the formula:
wherein M is a metal of Group 4, 5, or 6 of the Periodic Table preferably, zirconium, hafnium and titanium, most preferably zirconium;
R
1
and R
2
are identical or different, preferably identical, and are one of a hydrogen atom, a C
1
-C
10
alkyl group, preferably a C
1
-C
3
alkyl group, a C
1
-C
10
alkoxy group, preferably a C
1
-C
3
alkoxy group, a C
6
-C
10
aryl group, preferably a C
6
-C
8
aryl group, a C
6
-C
10
aryloxy group, preferably a C
6
-C
8
aryloxy group, a C
2
-C
10
alkenyl group, preferably a C
2
-C
4
alkenyl group, a C
7
-C
40
arylalkyl group, preferably a C
7
-C
10
arylalkyl group, a C
7
-C
40
alkylaryl group, preferably a C
7
-C
12
alkylaryl group, a C
8
-C
40
arylalkenyl group, preferably a C
8
-C
12
arylalkenyl group, or a halogen atom, preferably chlorine;
R
3
and R
4
are hydrogen atoms;
R
5
and R
6
are identical or different, preferably identical, are one of a halogen atom, preferably a fluorine, chlorine or bromine atom, a C
1
-C
10
alkyl group, preferably a C
1
-C
4
alkyl group, which may be halogenated, a C
6
-C
10
aryl group, which may be halogenated, preferably a C
6
-C
8
aryl group, a C
2
-C
10
alkenyl group, preferably a C
2
-C
4
alkenyl group, a C
7
-C
40
-arylalkyl group, preferably a C
7
-C
10
arylalkyl group, a C
7
-C
40
alkylaryl group, preferably a C
7
-C
12
alkylaryl group, a C
8
-C
40
arylalkenyl group, preferably a C
8
-C
12
arylalkenyl group, a —NR
2
15
, —SR
15
, —OR
15
, —OSiR
3
15
or —PR
2
15
radical, wherein R
15
is one of a halogen atom, preferably a chlorine atom, a C
1
-C
10
alkyl group, preferably a C
1
-C
3
alkyl group, or a C
6
-C
10
aryl group, preferably a C
6
-C
9
aryl group;
—B(R
11
)—, —Al(R
11
)—, —Ge—, —Sn—, —O—, —S—, —SO—, —SO
2
—, —N(R
11
)—, —CO—, —P(R
11
)—, or —P(O)(R
11
)—;
wherein:
R
11
, R
12
and R
13
are identical or different and are a hydrogen atom, a halogen atom, a C
1
-C
20
alkyl group, preferably a C
1
-C
10
alkyl group, a C
1
-C
20
fluoroalkyl group, preferably a C
1
-C
10
fluoroalkyl group, a C
6
-C
30
aryl group, preferably a C
6
-C
20
aryl group, a C
6
-C
30
fluoroaryl group, preferably a C
6
-C
20
fluoroaryl group, a C
1
-C
20
alkoxy group, preferably a C
1
-C
10
alkoxy group, a C
2
-C
20
alkenyl group, pref

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