Apparel – Body garments
Reexamination Certificate
1999-12-22
2001-09-11
Calvert, John J. (Department: 3741)
Apparel
Body garments
C002S079000, C002S082000, C442S381000, C128S873000
Reexamination Certificate
active
06286145
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to nonwoven fabrics used to make protective garments and protective garments made thereof. More particularly, the present invention relates to breathable nonwoven fabrics having a plurality of layers and protective garments made thereof.
BACKGROUND OF THE INVENTION
Protective garments or apparel is generally worn in industrial settings, although it may be worn in other environments, such as hospitals, health-care facilities, farms, food processing plants, accident sites, hazardous waste sites, homes or anywhere a person may encounter pathogens, chemicals, dusts, smoke or irritants. These garments are exposed to a variety of hazards, and as a result, typically require sufficient strength to resist tears, rips and puncture.
Materials used to manufacture these garments are often designed to act as a barrier to liquids thereby providing protection from industrial chemicals, pathogens, irritants and the like. In this regard, some fabrics have the ability to act as a barrier to liquids while at the same time remaining “breathable” in the sense that water vapor may pass through the fabric. Breathable materials are often desired in many products such as, for example, in industrial workwear garments because a breathable garment helps prevent the build-up of moisture next to the worker's body, and thus, are generally more comfortable to wear than similar non-breathable apparel. A barrier layer that may be a breathable film or a very fine fiber nonwoven web can provide the breathable barrier properties. However, as the level of breathability increases the strength of the barrier layer typically decreases. Moreover, breathable barrier layers are often materials that have little inherent strength. They tend to be very fragile or easily damaged by abrasion, stretching and/or tearing forces. Additionally, the breathable barrier layers are often heat sensitive and are difficult to thermally bond to other higher-strength materials. Adhesives may be used to join breathable barrier layers with other materials. Unfortunately, adhesives tend to be expensive, may reduce breathability, can lose adhesion when exposed to certain solvents or environments, and may require heat curing that can thermally damage sensitive films. Thus, many breathable fabrics fail to provide sufficient barrier properties and are prone to leak when subjected to intense rain, abrasion, stretching or other harsh conditions.
Accordingly, a fabric that has sufficient strength and provides sufficient breathability and barrier properties will be an improvement over conventional fabrics used in personal protective garments.
DEFINITIONS
As used herein, the term “comprises” refers to a part or parts of a whole, but does not exclude other parts. That is, the term “comprises” is open language that requires the presence of the recited element or structure or its equivalent, but does not exclude the presence of other elements or structures. The term “comprises” has the same meaning and is interchangeable with the terms “includes” and “has”.
As used herein, the terms “liquid impermeable,” “liquid impervious” or “barrier” refers to a material that does not allow a liquid, such as water, to readily pass therethrough. Such a material has a minimum hydrostatic head value of at least about 30 mbar. Hydrostatic head or hydrohead as used herein refers to a measure of the liquid barrier properties of a fabric. Hydrohead is measured using a hydrostatic pressure test that determines the resistance of nonwoven materials to penetration by water under low hydrostatic pressure. Generally speaking, the test procedure is in accordance with Method 5514-Federal Test Methods Standard No. 191A, AATCC Test Method
127-89
and INDA Test method 80-4-92, modified to include a screen support of standard synthetic fiber window screen material. A test head of a Textest FX-300 Hydrostatic Head Tester (Schmid Corp., Spartanburg, S.C.) is filled with purified water maintained at a temperature between about 60° F. and 85° F. (18.3° C. and 29.4° C.). The testing is conducted at normal ambient conditions (about 73° F. (23° C.) and about 50% relative humidity). An 8-inch×8-inch (20.3 cm×20.3 cm) square sample of the test material is placed such that the test head reservoir is covered completely. The sample is subjected to a standardized water pressure, increased at a constant rate until leakage is observed on the outer surface of the sample material. Hydrostatic pressure resistance is measured at the first sign of leakage in three separate areas of the sample. The test is repeated for five specimens of each sample material. The results are averaged for each specimen and recorded in millibars. A fabric with a higher hydrohead reading indicates it has a greater resistance to liquid penetration than a fabric with a lower hydrohead. Fabrics having a greater resistance to liquid penetration are generally thought to also have useful levels of resistance to penetration by particulates (e.g., dusts and powders or the like).
As used herein the term “UV stable” refers to a polymeric composition that retains at least 40% (corrected) of its tensile strength after 12 months of exposure. UV stability may be assessed by a South Florida test that may be conducted by exposing a nonwoven fabric to the sun with no backing in Miami, Fla. The samples face south at a 45-degree angle. Each cycle concludes with a modified tensile test to measure the degradation or change in strength of the fabric. This provides a measure of the durability of the fabric. Comparing the length of time the web retains at least 40% (corrected) of its tensile strength can assess the relative UV stability. The tensile strength of a fabric may be measured according to the ASTM test D-1682-64. In addition, calculation of corrected 40% tensile strength may be obtained by adding the sum of the months to 50, 40 and 30% retention of tensile strength and dividing by three.
As used herein, the term “breathable” refers to a material which is permeable to water vapor having a minimum “moisture vapor transmission rate” or MVTR of at least about 100 g/m
2
/24 hours. The MVTR of a fabric is also often generally referred to as the “water vapor transmission rate” or WVTR. Generally speaking, materials used in protective garments such as industrial workwear will desirably have a MVTR of greater than 1000 g/m
2
/24 hours. For example, useful fabrics will have a MVTR ranging from about 2000 to about 5000 g/m
2
/24 hours. Some fabrics may have MVTR values ranging as high as about 6000 or 7000 g/m
2
/24 hours. Even greater MVTR values are desirable if it does not compromise the barrier properties of the fabric.
As used herein, the term “nonwoven web” refers to a web that has a structure of individual fibers that are interlaid forming a matrix, but not in an identifiable repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes known to those skilled in the art such as, for example, meltblowing, spunbonding, wet-forming and various bonded carded web processes.
As used herein, the term “spunbond web” refers to a web formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries with the diameter of the extruded filaments then being rapidly reduced, for example, by fluid-drawing or other well known spunbonding mechanisms. The production of spunbond nonwoven webs is illustrated in patents such as Appel, et al., U.S. Pat. No. 4,340,563.
As used herein, the term “meltblown web” means a web having fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten fibers into a high-velocity gas (e.g. air) stream which attenuates the fibers of molten thermoplastic material to reduce their diameters. 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 fibers. The meltblown process is well-known and is described in v
DeLucia Mary Lucille
Welchel Debra Nell
Wright Alan Edward
Calvert John J.
Kimberly--Clark Worldwide, Inc.
Muromoto Jr. Robert H.
Sidor Karl V.
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