Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1998-10-09
2001-02-20
Weiss, John G. (Department: 3762)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S221000, C442S394000, C604S367000
Reexamination Certificate
active
06190758
ABSTRACT:
BACKGROUND OF THE INVENTION
Thermoplastic resins have been extruded to form fibers, films and webs for a number of years. The most common thermoplastics for these applications are polyolefins, particularly polypropylene and polyethylene, though each material has its characteristic advantages and disadvantages vis a vis the properties desired in the final products.
Nonwoven fabrics are one type of product which can be made from such polymers and are useful for a wide variety of applications such as personal care products like diapers, feminine hygiene products and incontinence products, infection control products, garments and many others. The nonwoven fabrics used in these applications are often in the form of laminates having various numbers of layers of meltblown fabric, spunbond fabric and/or films like spunbond/meltblown/spunbond (SMS) laminates, SMMS laminates, spunbond/film (SF) and SFS laminates and even laminates having 6 or more layers.
One disadvantage to, in particular, SF laminates, is that they can delaminate under certain conditions. Such delamination is, of course, undesirable, as it can result in product failure. There remains a need for a spunbond/film laminate which is lightweight and thin yet also provides adequate adhesion between the layers such that delamination does not occur.
It is an object of this invention to provide laminates having at least one layer of a nonwoven fabric with at least one layer of a film where the laminate exhibits greater delamination or peel strength than heretofore known similar laminates.
SUMMARY OF THE INVENTION
There is provided herein a multilayer laminate comprised of a layer of a film and a layer of nonwoven fabric. The film is made from polymers and has as one surface a semi-crystalline/amorphous or “heterophasic” polymer, an optional inner, less expensive, filler type polymer, and as the other surface, a polymer with a lower coefficient of friction. The nonwoven fabric may be a spunbond or meltblown fabric, preferably spunbond and preferably also including a heterophasic polymer. The film and nonwoven components are bonded together using thermal point bonding preferably while the film is stretched at least 5 percent. Such a laminate may be made into a personal care product like a diaper, training pant, absorbent underpants, adult incontinence product, and feminine hygiene product.
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. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of a fiber. For example, the diameter of 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. No. 3,502,763 to Hartman, U.S. Pat. No. 3,502,538 to Levy, and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbound fibers are generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and have diameters larger than 7 microns, more particularly, between about 10 and 20 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 converging high velocity gas (e.g. air) streams which attenuate 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 may be continuous or discontinuous, are generally tacky when deposited onto a collecting surface.
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 “heterophasic” in reference to a polymer means a thermoplastic polymer which has both elastic and plastic properties. Such polymers are sometimes referred to as “plasto-elastic” or “elastoplastic” polymers and may be semi-crystalline/amorphous in character. These polymers posses a comprise of elastic properties and mechanical resistance and can easily be transformed into manufactured articles by using the apparatus and processes normally used for thermoplastic materials.
As used herein the term “monocomponent” fiber refers to a fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which small amounts of additives have been added for coloration, anti-static properties, lubrication, hydrophilicity, etc. These additives, e.g. titanium dioxide for coloration, are generally present in an amount less than 5 weight percent and more typically about 2 weight percent.
As used herein the term “conjugate fibers” refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Conjugate fibers are also sometimes referred to as multicomponent or bicomponent fibers. The polymers are usually different from each other though conjugate fibers may be monocomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the conjugate fibers and extend continuously along the length of the conjugate fibers. The configuration of such a conjugate 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. Conjugate 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 U.S. Pat. No. 5,382,400 to Pike et al. For two component fibers, the polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios.
As used herein the term “bioconstituent 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. Biconstituent fibers do not have the various polymer components arranged in relatively constantly positioned distinct zones across the cross-se
Cho David J.
Herrick William D.
Kimberly--Clark Worldwide, Inc.
Moyles Lisa J.
Robinson James B.
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