Patent Application
20110097571
The present invention relates generally to sheet materials, which can be referred to as membranes or films, and more particularly, to sheet materials that have qualities such as being oil penetration resistant, water penetration resistant, water vapor permeable, air permeable and resistant to significant property degradation resulting from chemical presence.
Fluoropolymers and thermoplastic elastomers are known and are used in many different applications, including outdoor sheet materials or films. A layer of fluoropolymer or a layer of thermoplastic elastomer may be utilized to provide some desired properties, such as water vapor and air-permeable (e.g., breathability) or resistance to water penetration. Thus, it is known to provide a breathable and water resistant sheet material. Such a sheet material is very useful in active outdoor applications. For example, such sheet material can be used to make articles of clothing, outdoor gear, protective articles and the like. However, the presence of some chemicals, such as insect repellant, may cause degradation of at least some of the properties of the sheet material, such as the level of water penetration resistance. Specifically, the propensity that the sheet material will permit penetration/passage of water will be increased due to the chemical presence on the sheet material. Such increased propensity to permit penetration/passage of water may be referred to as wetting out.
The following presents a simplified summary of the invention in order to provide a basic understanding of some example aspects of the invention. This summary is not an extensive overview of the invention. Moreover, this summary is not intended to identify critical elements of the invention nor delineate the scope of the invention. The sole purpose of the summary is to present some concepts of the invention in simplified form as a prelude to the more detailed description that is presented later.
In accordance with one aspect, the present invention provides a porous composite membrane that includes a first microporous substrate of a first material. A second, coating material is joined to the first microporous substrate and is a second microporous substrate to form a bi-component arrangement with the first microporous substrate. The second material is different than the first material. A third, coating material is applied to the bi-component arrangement. The third material is different than the first and second materials. The third material extending over at least a portion of surfaces of the bi-component arrangement which define the micropores.
In accordance with another aspect, the present invention provides an associated method of providing the porous composite membrane.
The foregoing and other aspects of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which:
Example embodiments that incorporate one or more aspects of the present invention are described and illustrated in the drawings. These illustrated examples are not intended to be a limitation on the present invention. For example, one or more aspects of the present invention can be utilized in other embodiments and even other types of devices. Moreover, certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. Still further, in the drawings, the same reference numerals are employed for designating the same elements.
Turning to
Focusing upon the porous substrate 12, the substrate has air-permeable, vapor-permeable and waterproof characteristics. Pores 20 of the substrate 12 are micropores. See
Focusing upon the thermoplastic layer 14 (see
In one embodiment of this disclosure, to provide the thermoplastic layer 14 onto the sheet material 10, the layer 14 is heated to at least partially melt. While in the at least partially melted state, the layer material flows into pores of the substrate 12. The coating layer material only proceeds partially into the substrate 12. This partial flow into the substrate 12 is schematically indicated in
The material of the layer 14 adheres to fibrils 22 and nodes 24 of the material of the substrate 12.
In one example, the heating of the layer 14 is performed in a series of heating steps. In one specific example the heating includes heating at a first temperature, subsequently heating at a second temperature that is higher than the first temperature, and then subsequently heating at a third temperature that is higher than the second temperature. A specific example of the multi-temperature heating includes heating at the first temperature in the range of 80-90° C., subsequently heating at the second temperature in the range of 90-110° C., and subsequently heating at the third temperature in the range of 110-150° C.
The heating of the layer 14 may be accomplished via different methods. In one example, the heating is accomplished in conjunction with application of pressure to the sheet material. In one specific example, the heating and pressure may be imparted via passing an intermediate-step sheet material 10 (i.e., the substrate 12 with the layer 14 applied but not yet heated) through heated press rollers. Such an approach of using heated rollers is useful if the sheet material 10 is manufactured as an elongate web. The elongate web of sheet material may be moved to pass between the heated rollers at a web speed so that large quantities of the sheet material may be produced in an economical manner. With the regard to the specific example of providing heat in a series of steps, the heating may be accomplished via a series of heated rollers, with each roller providing a different heating level. Of course, other forms of heating and pressure application, such as non-dynamic heating and pressing, are contemplated and within the scope of the present invention.
With reference to
The oleophobic and hydrophobic coating 16 attaches to join to at least some of the thermoplastic layer material 14 and the polymer substrate material 12. Specifically, the oleophobic coating 16 attaches to the material of the thermoplastic layer 14 and the material of the polymer substrate 12 at the microporosity level. By this the oleophobic coating 16 does not lay upon an exterior of the thermoplastic layer 14 and/or the polymer substrate 12. Instead the oleophobic coating 16 is penetrated into the material of the thermoplastic layer 14 and the material of the polymer substrate 12. Again with reference to the example of
The oleophobic coating 16 may be fluoroacrylate-based or siloxane-based polymers or other oleophobic material. In general, the material of the coating 16 includes at least one of polyurethane, fluorinated acrylate, fluorinated methacrylate, siloxane-based polymer, polyacrylic acid, copolymers of acrylamide. The material may be a thermoplastic or a thermoset. In one example, oleophobic coating material 16 is introduced into the sheet material 10 in a dissolved state. Also, as an example, the oleophobic coating material 16 is introduced into the sheet material 10 in condition that may be considered fluid to permit motion/movement. In one specific example, the oleophobic coating material 16 is dissolved by pressurized fluid of carbon dioxide under supercritical conditions and moves oleophobic coating material into the porous substrate 12 and/or porous layer 14. The oleophobic coating is attached/deposited into the porous substrate 12 and/or porous layer 14 by lowering the pressure from supercritical to non-supercritical condition.
It is to be appreciated that the process of making the overall end product may be varied. For example, the material of the coating 16, may be applied various techniques including dispersion in a fluid, with the aid of a liquid carrier, and deposited by precipitation from a supercritical fluid, liquid, or gas. If a liquid carrier is used, the carrier may be either an organic solvent or an inorganic solvent. It is to be noted that with the use of a supercritical solvent, the solvent may be carbon dioxide in either fluid, liquid, or gas state. As such, the process may include many different techniques such as utilizing chemical vapor deposition, plasma, knife coating process, transfer coating process, screen printing process, and gravure roll printing process. Even other techniques are possible and contemplated.
The final treated (i.e., layered and coated) substrate remains porous making the sheet material 10 moisture vapor permeable, air permeable, waterproof, durable, resistant to chemical penetration, and oleophobic. The final sheet or membrane has an air permeability of at least 0.1 cfm per square foot of surface area of one side of the composite membrane at 1,000 Pascals differential pressure. This is due in part to the micropores being less than 100 microns. The final sheet material can be combined with optional layers, such as nonwoven and woven fabrics, yarns, knitted fabrics, for different consumer, professional, and industrial applications.
Within the prepared sheet material 10, the characteristics of waterproofness, water vapor permeability, air permeability are provided. Waterproofness is the commonly understood terminology associated with the ability to prevent non-vapor water from penetrating the sheet material. Water vapor permeability is the ability to permit passage of water vapor through the sheet material. Air permeability is the ability to permit passage of air through the sheet material. Moisture vapor transmission rate, also known as MVTR, is a measure of the passage of water vapor through a sheet material expressed in grams/meter2/day. Air permeability, expressed in cubic feet per minute, measures the time it takes for air to pass through the sample at a predetermined pressure drop of water across the sample. A high MVTR and air permeability results in good comfort levels since sweat and body heat pass through the membrane and are permitted to quickly move from adjacent the body.
At least one of the materials of the layer 14 and the coating material 16 changes oil repellent properties of the substrate 12. In particular, such properties are enhanced. At least one of the materials of the layer 14 and the coating material 16 increases resistance to liquid chemical intrusion into or through the pores of the substrate 12. In accordance with one aspect of the present invention, waterproofness, water vapor permeability, air permeability are provided even if a chemical that would otherwise degrade resistance to water penetration of the sheet material 10. The chemical may be considered to be a challenge agent. Such a challenge agent has at least a potential to cause an adverse affect to at least one desirable characteristic. In a specific example, the challenge agent has at least the potential to adversely affect the characteristic of being waterproof. A loss of waterproofness is associated with wetting and water penetration. By this, wetting-out could occur that would allow passage of non-vapor or liquid water. Accordingly, it is to be understood that reference to a chemical may be considered to include an understanding that the chemical is such a challenge agent. A resistance to degradation by chemical (challenge agent) is indicated by Mullen test rating (ASTM D751).
One widely used example chemical (i.e., challenge agent) that could cause the degradation of the non-vapor water penetration resistance (i.e., waterproofness) of the sheet material 10 is N,N-Diethyl-meta-toluamide, also known as DEET. Other examples of chemicals that could cause degradation include chemicals present include engine fuels (e.g., aviation, automotive, diesel) and solvents. Still further, other chemical contaminants, such as a variety of acids, are also contemplated. As mentioned, such chemicals are sometimes referred to as challenge agents because of their propensity to degrade desirable material properties. Of course the particular chemical challenge agents are not limitations on the present invention. Such chemicals, if present on the sheet material 10 would otherwise cause the microporous material of the substrate 12 to permit passage of water droplets, but one aspect of the present invention prevents such unwanted occurrence (i.e., loss of waterproofness) and thus provides a resistance to such chemicals.
DEET is a common active ingredient in insect repellents and has a relatively low surface tension that could “foul” the substrate 12 and sheet material 10 and permit the passage of liquid water therethrough. Since the sheet material 10 may be used in outdoor applications, such as in gloves, boots, tents, etc., it is beneficial for the sheet material 10 to be resistant to degradation of the waterproof property from a chemical challenge agent, such as DEET, used in insect repellant. This resistance to degradation allows the sheet material 10 to retain its waterproof, vapor permeable, and air permeable characteristics despite the presence of the chemical. Also, the sheet material 10 may be used in applications where sheet materials may contact an engine fuel (e.g., diesel fuel). Again, is it is beneficial for the sheet material 10 to be resistant to degradation of the waterproof property from a chemical challenge agent such as engine fuel.
The sheet material 10 can retain the resistance to degradation even after many hours of exposure to the challenge agent. Data for some example sheet materials includes ePTFE alone, before and after treatment with Supercritical CO2 with Fluoro-polymer, ePTFE with just a thermoplastic polyurethane layer (i.e., no treatment with Supercritical CO2 with Fluoro-polymer), and two examples in accordance with the present invention (e.g., ePTFE coated with microporous thermoplastic polyurethane and treated with oleophobic coating) is shown in tables 1A-1C. As such, at least one the materials of the layer 14 and the coating 16 changes the hydrophobic or water repellent properties of the substrate 12. Along these lines at least one the materials of the layer 14 and the coating 16 changes the coefficient of friction of the substrate 12.
The final sheet material 10 may have a thickness between major surfaces of less than 100 micron, or 0.1 millimeters. Of course, such an example dimension need not be a limitation upon the present invention. This low thickness, along with a light weight, adds to the comfort level of the sheet material 10. In fact, at least one the materials of the layer 14 and the coating material 16 may enhance the mechanical properties of the polymer substrate 12. The sheet material 10 may also be combined with another fabric layer on both sides for use in the construction of outerwear, such as gloves, boots, tents, etc. In fact, at least one the materials of the layer 14 and the coating material 16 could provide for interfacial bonding to another porous substrate. Example uses of the sheet material 10 include, but are not limited to, gloves, hats, coats, jackets, shirts, pants, under garments, shoes, boots, protective wear, various other articles of clothing, backpacks, sleeping bags, tents, various other outdoor gear, and the like.
With regard to uses that involve something worn by a person, it is must be appreciated that as the person sweats both water vapor and liquid perspiration are generated on the skin. In such an application it is contemplated that the coating layer would innermost, toward the person and the substrate 12 would be outermost, away from the person. A high MVTR and air permeability may provide for this water vapor and liquid sweat to quickly pass through the sheet material 10. As such, the sheet material is quite useful for the use examples mentioned above concerning items that are worn by a person. Of course, the present invention is not limited to such uses and other uses are contemplated. Also, it is contemplated that the sheet material may include additional layers and/or the sheet material may be incorporated into multilayer sheet. Some examples of such additions to the sheet material and/or the use of sheet material being included into a multilayer sheet include the use of at least one of woven fabrics, nonwoven fabrics, knitted fabrics, and yarn. Of course, other materials and/or fabrics are contemplated.
The invention has been described with reference to the example embodiments described above. Modifications and alterations will occur to others upon a reading and understanding of this specification. Examples embodiments incorporating one or more aspects of the invention are intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.
