Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Needled nonwoven fabric
Reexamination Certificate
1997-04-02
2001-07-31
Pezzuto, Helen L. (Department: 1713)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Needled nonwoven fabric
C442S395000, C442S398000, C442S400000, C442S401000, C442S403000, C442S415000
Reexamination Certificate
active
06268302
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a nonwoven fabric or web which is formed from spunbond fibers of a thermoplastic resin and laminates using such a web as a component.
Thermoplastic resins have been extruded to form fibers, fabrics and webs for a number of years. The most common thermoplastics for this application are polyolefins, particularly polypropylene. Other materials such as polyesters, polyetheresters, polyamides and polyurethanes are also used to form spunbond fabrics.
Nonwoven fabrics or webs are useful for a wide variety of applications such as diapers, feminine hygiene products, towels, and recreational or protective fabrics. The nonwoven fabrics used in these applications are often in the form of laminates like spunbond/spunbond (SS) laminates or spunbond/meltblown/spunbond (SMS) laminates.
One of the desired characteristics of nonwoven fabrics is that they be as soft as possible. Previously, improving softness has generally involved a trade-off with other desirable properties of the web such as tensile strength. For example, polyethylene webs are very soft but also quite weak.
It is an object of this invention to provide a spunbond polyolefin nonwoven fabric or web which is softer than those conventionally produced but which has comparable strength characteristics.
SUMMARY OF THE INVENTION
A soft and strong nonwoven spunbond polyolefin fabric is provided which is a multilayer laminate of a first web of high melt flow polymer fibers and a second web of low melt flow polymer fibers. The web of low melt flow polymer fibers is produced from polyolefin polymer having a melt flow rate of below 50 grams/10 minutes at 230° C. The web of high melt flow polymer fibers is produced from polyolefin polymer having a melt flow rate of at least 50 grams/10 minutes at 230° C. wherein the polyolefin polymer is initially produced as a reactor granule through the use of a Ziegler-Natta catalyst with a melt flow rate below 50 grams/10 minutes at 230° C. and subsequently modified by a method such as the addition of up to 1000 ppm of peroxide, the addition of up to 5 weight percent of an organo-metallic compound and the addition of up to 5 weight percent of a transition metal oxide. This treatment increases the melt flow rate of the polymer by a factor of at least two. Such a laminate has a tensile strength of at least 10% greater than a similar laminate made without a high melt flow rate web but instead with a web of the same type as the second web. The fabric of this invention may also have various layers disposed between the first and second webs.
The nonwoven fabric of this invention may be used in products such as, for example, garments, personal care products, medical products, protective covers and outdoor fabrics.
In a further aspect a soft and strong nonwoven spunbond polyolefin fabric is provided comprising: a first web of spunbond fibers produced from a polyolefin polymer having a melt flow rate of at least 50 grams/10 minutes according to ASTM D-1238-90b condition L and a viscosity of at least 2500 dynes.sec/cm
2
and; a second web of spunbond fibers produced from a polyolefin polymer having a melt flow rate below 50 grams/1 0 minutes according to ASTM D-1238-90b condition L wherein said webs are bonded together to form a laminate having a strength at least 10% greater than the same laminate made when the first web polymer melt flow rate does not exceed 50 grams/10 minutes according to ASTM D-1238-90b condition L. In addition, the fabric may further comprise a third layer selected from the group consisting of meltblown webs and films disposed between the first and second webs. In a further aspect, the meltblown web or film may be made from fiber forming or film forming polymers, respectively, selected from the group consisting of polyurethanes, polyetheresters, polyamides, polyolefins, polyolefin copolymers and mixtures thereof
DEFINITIONS
As used herein the term “nonwoven fabric or web” means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91).
As used herein the term “microfibers” means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 0.5 microns to about 50 microns, or more particularly, microfibers may have an average diameter of from about 2 microns to about 40 microns. The diameter of, for example, a polypropylene fiber given in microns, may be converted to denier by squaring, and multiplying the result by 0.00629, thus, a 15 micron polypropylene fiber has a denier of about 1.42 (15
2
×0.00629=1.415).
As used herein the term “spunbonded fibers” refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinnerette with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. Nos. 3,502,763, and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbond fibers are generally continuous and larger than 7 microns, more particularly, they are usually between about 15 and 50 microns.
As used herein the term “meltblown fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity gas (e.g. air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly disbursed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin. Meltblown fibers are microfibers which are generally smaller than 10 microns in diameter. The term meltblowing used herein is meant to encompass the meltspray process.
As used herein the term “polymer” generally includes but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configuration of the material. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries.
As used herein the term “bicomponent fibers” refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the bicomponent fibers and extend continuously along the length of the bicomponent fibers. The configuration of such a bicomponent fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side by side arrangement or an “islands-in-the-sea” arrangement. Bicomponent fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 5,336,552 to Strack et al., and European Patent 0586924. The polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios.
As used herein the term “biconstituent fibers” refers to fibers which have been formed from at least two polymers extruded from the same extruder as a blend. The term “blend” is defined below. Biconst
DeLucia Mary Lou
Hudson Robert Leslie
Kobylivker Peter Michailovich
Ofosu Simon Kwame
Sayovitz John Joseph
Dean, Jr. Ralph H.
Kimberly--Clark Worldwide, Inc.
Pezzuto Helen L.
Tulley, Jr. Douglas H.
LandOfFree
High strength spunbond fabric from high melt flow rate polymers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High strength spunbond fabric from high melt flow rate polymers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High strength spunbond fabric from high melt flow rate polymers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454187