Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D5/00—Composition of materials for coverings or clothing affording protection against harmful chemical agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/22—Layered products comprising a layer of synthetic resin characterised by the use of special additives using plasticisers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
  • B32B27/285—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42 comprising polyethers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
  • B32B27/286—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42 comprising polysulphones; polysulfides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
  • B32B5/022—Non-woven fabric
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
  • B32B5/024—Woven fabric
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
  • B32B7/14—Interconnection of layers using interposed adhesives or interposed materials with bonding properties applied in spaced arrangements, e.g. in stripes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0261—Polyamide fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/02—Synthetic macromolecular fibres
  • B32B2262/0261—Polyamide fibres
  • B32B2262/0269—Aromatic polyamide fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/06—Vegetal fibres
  • B32B2262/062—Cellulose fibres, e.g. cotton
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/30—Properties of the layers or laminate having particular thermal properties
  • B32B2307/306—Resistant to heat
  • B32B2307/3065—Flame resistant or retardant, fire resistant or retardant
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/704—Crystalline
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/732—Dimensional properties
  • B32B2307/734—Dimensional stability
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2571/00—Protective equipment

Definitions

• the present invention relates to laminates prepared in part from continuous N-alkylchitosan films.
• the laminates are useful for fabrication as a protective article and are preferably substantially impermeable to hazardous chemical and biological agents, but sufficiently permeable to water vapor that, if worn as protective apparel, it is both protective and comfortable to wear.
• N-alkylchitosans with up to six carbons and different degrees of substitution of the N-alkyl group were prepared by T. Uragami et al. in a study of N-alkylchitosan membranes for pervaporation of aqueous ethanol solutions (Journal of Membrane Science 124 (1997) 203-211 ).
• the present invention provides selectively permeable laminates that contain a continuous N-alkylchitosan film and that can be used in articles for personal protection, providing improved wearer comfort compared with impermeable articles.
• One aspect of the present invention is a method of inhibiting the permeation of a chemically or biologically harmful agent through a laminate or a structure or item of apparel fabricated therefrom, by including within the laminate a continuous N-alkylchitosan film
• Another aspect of the present invention is a protective structure comprising a continuous N-alkylchitosan film.
• the structure is a laminate further comprising at least one layer of fabric.
• a further aspect of the present invention is a finished article incorporating a laminate that comprises a continuous N-alkylchitosan film and at least one layer of fabric.
• Finished articles include items of apparel, shelters, and protective covers.
• Figure 1 is a schematic diagram showing the structure of one type of selectively permeable laminate according to an embodiment of the present invention.
• film means_a thin but discrete structure that moderates the transport of species in contact with it, such as gas, vapor, aerosol, liquid and/or particulates.
• a film may be chemically or physically homogeneous or heterogeneous. Films, as used herein, are less than about 0.25 mm th ⁇ ick ⁇
• N-alkylchitosan as used herein includes N-alkylated chitosan-based moieties, including the N-alkylchitosans themselves, and their salts and derivatives.
• the alkyl group may be 1 to 12 carbons in length.
• N-alkylchitosan film as used herein means a film that contains at least one N-alkylchitosan-based moiety in the amount of at least 50% by weight.
• nonporous denotes a material or surface that does not allow the passage of air other than by diffusion.
• continuous N-alkylchitosan film as used herein means an N-alkylchitosan film having at least one nonporous surface.
• permeable means allowing liquids or gases to pass or diffuse through.
• the term "selectively permeable” as used herein means allowing passage of certain species but acting as a barrier to others.
• the protective structures disclosed herein are selectively permeable in that they are permeable to water vapor but have minimal or no permeability (thus, act as a barrier) to chemical agents.
• laminate as used herein means a material comprising two or more parallel layers of material that are at least partially bonded to each other.
• substrate as used herein means the material onto which a film is formed from solution.
• work device denotes a substrate which is used only for film formation and does not subsequently become part of a laminate.
• soluble denotes a material that forms a visibly transparent solution when mixed with a specified solvent.
• a water-soluble material forms a transparent solution when mixed with water, while a water-insoluble material does not.
• N-alkylchitosan solution indicates that at least one N-alkylchitosan moiety is dissolved in the indicated solvent. However, materials that are insoluble in the indicated solvent may also be present.
• (in)solubilize means to render a material (in)soluble in a specified solvent.
• toxin means a poisonous substance, typically a protein or mixture of proteins, produced by a living organism (e.g., plants, animals, or pathogenic bacteria.
• a toxin typically has a high molecular weight (as compared to a simple chemical poison), is antigenic (elicits an antibody response), and is highly poisonous to living creatures.
• harmful to human health means causing injury to humans as a consequence of acute or chronic exposure through dermal contact, ingestion, or respiration.
• the N-alkylchitosan films and laminates made therefrom are substantially impermeable to certain biological and/or chemical agents. It is often desirable that the films and laminates be at least 99% impermeable to certain agents, even up to 100% impermeable.
• the present invention provides a protective structure, fabricated from a continuous N-alkylchitosan film or a selectively permeable laminate containing a continuous N-alkylchitosan film.
• Structure as used herein with regard to structures fabricated from the continuous N-alkylchitosan film, includes single layers and multiple layers of continuous N-alkylchitosan films. These films can be used to make laminates.
• the structures can be used in articles and items of apparel that protect against exposure to a chemical or biological agent that is harmful to human health. Specific embodiments include finished articles, including articles of apparel, fabricated from a continuous N-alkylchitosan film or a selectively permeable laminate containing a continuous N- alkylchitosan film.
• the invention provides methods of inhibiting the permeation of a chemically or biologically harmful agent through a selectively permeable laminate, or through an article or item of apparel fabricated therefrom, by including within the selectively permeable laminate a continuous N-alkylchitosan film.
• the invention provides methods of fabricating a structure that protects against exposure to a chemical or biological agent that is harmful to human health, and methods of fabricating items of apparel, by incorporating into a structure or item of apparel a selectively permeable laminate containing an N-alkylchitosan film. Because the laminates are selectively permeable, we have found that a structure fabricated therefrom provides a protective barrier that inhibits the permeation through the laminate, and thus through the structure, of chemical and biological agents that may be harmful to humans while maintaining sufficient water vapor permeability to maintain personal comfort when the laminate is used to fabricate an item of apparel.
• the selectively permeable laminates described herein contain a continuous N-alkylchitosan film.
• the laminate is an N- alkylchitosan film deposited from solution onto a substrate.
• the laminate is an N-alkylchitosan film adhered to a layer, for example, polyurethane film by thermal bonding.
• a continuous N-alkylchitosan film or an N-alkylchitosan film cast onto a substrate, or an N-alkylchitosan film thermally bonded to another layer is bonded to one or more layers of fabric, by adhesive.
• the adhesive can be in the form of stripes or, preferably, dots, to provide a discontinuous layer of adhesive, in order not to block passage of gases and/or liquids through the selectively permeable laminate.
• Figure 1 illustrates one embodiment of a selectively permeable laminate that could be used in, for example, an article of apparel.
• the laminate contains the following elements a continuous N-alkylchitosan film (1 ); a substrate to which the continuous N-alkylchitosan film is adhered (2); additional layers (3, 3'); an inner liner (4); an outer shell (5) and adhesive (6,6').
• the selectively permeable laminates contain all of the elements shown in Figure 1. .
• Chitosan is the commonly used name for poly- [1 -4]- ⁇ -D- glucosamine. It is commercially available and is chemically derived from chitin, which is a poly- [1 -4]- ⁇ -N-acetyl-D-glucosamine that, in turn, is derived from the cell walls of fungi, the shells of insects and, especially, crustaceans.
• chitin a poly- [1 -4]- ⁇ -N-acetyl-D-glucosamine that, in turn, is derived from the cell walls of fungi, the shells of insects and, especially, crustaceans.
• acetyl groups are removed by treatment with strong base, and, in the chitosan used herein, the degree of deacetylation is at least about 60%, and is preferably at least about 85%. As the degree of deacetylation increases, it becomes easier to dissolve chitosan itself in acidic media.
• N-alkylated chitosans have been prepared with alkyl groups from 1 to 12 carbons long and with varying degrees of N-substitution (Uragami, op cit; R. A. A. Muzzarelli et al., Journal of Membrane Science 16 (1983) 295-308; D. de Britto and O. B. G. de Assis, International Journal of
• N,N-dimethylchitosan can be prepared by reacting chitosan with formaldehyde in the presence of formic acid (see, e.g., U. S. Patent No. 4,826,826). Quaternized forms, e.g., N,N,N-trimethyl- and N,N,N,-thethylchitosan salts have also been prepared by, for example, R. A. A. Muzzarelli and F.
• Tanfani (Carbohydrate Polymers 5(4) (1985)297-307), A. B. Sieval et al. (Carbohydrate Polymers 36 (1998) 157-165) and L. A. Nud'ga et al. (Zhurnal Obshchei Khimii 43(12) (1973) 2756-60).
• Chitosan can also be converted to N-methylchitosan by the reaction of chitosan with a methylating agent, such as dimethyl sulfate, methyl iodide, trimethylphosphate and the like, usually carried out in the presence of a base.
• a methylating agent such as dimethyl sulfate, methyl iodide, trimethylphosphate and the like
• bases include alkaline or alkaline earth hydroxides or carbonates.
• This chemical transformation can be carried out on chitosan powder to yield N-methylchitosan powder, which is then washed and dried.
• the N-methylchitosan powder is then converted to film by dissolving it in a solvent to form a solution, casting the solution, drying, and, optionally, treating the film with base and/or heating to convert the N-methylchitosan film to an insoluble form.
• a preformed chitosan film can be directly converted to N-methylchitosan by applying the
• N-alkylchitosan-based moieties that are suitable for use in the embodiments described herein include N-alkylchitosan itself, N- alkylchitosan salts, and N-alkylchitosan derivatives.
• Representative examples of chitosan derivatives suitable for use in this invention include O-carboxymethylated N-alkylated chitosans (N. Song et al., Zhongguo Haiyang Yaowu 20(1 ) (2001 ) 32-33, 41 ).
• the number average molecular weight (M n ) in aqueous solution of the N-alkylchitosan used herein is at least about 10,000.
• N-alkylchitosan film may be cast from solution. If it is desired to cast an N-alkylchitosan film from an aqueous solution, however, the N- alkylchitosan is first solubilized, since N-alkylchitosan itself is not soluble in water. Preferably, solubility is obtained by adding the N-alkylchitosan to a dilute solution of a water-soluble acid.
• N-alkylchitosan to react with the acid to form a water-soluble salt, herein referred to as an "N- alkylchitosan salt” or “N-alkylchitosan as the (acid anion) thereof, for example "N-alkylchitosan as the acetate thereof if acetic acid was used.
• N-alkylchitosan derivatives such as O-carboxyalkyl N-alkylchitosans that are water-soluble can be used directly in water without the addition of acid.
• the acid used to solubilize the N-alkylchitosan may be inorganic or organic.
• suitable inorganic acids include without limitation hydrochloric acid, sulfamic acid, hot sulfuric acid, phosphoric acid and nitric acid.
• Suitable organic acids may be selected from the group consisting of water-soluble mono-, di- and polycarboxylic acids. Examples include without limitation formic acid, acetic acid, pimellic acid, adipic acid, o-phthalic acid, and halogenated organic acids. Other suitable acids are disclosed in US Patent 2,040,880. Mixtures of acids may also be used. Volatile acids, that is, those with a boiling point less than about 200 0 C, are preferred.
• the amount of acid used to solubilize the N-alkylchitosan can be chosen to control the viscosity. If too little acid is added, the resulting solution may be too viscous to cast a thin film and/or to be filtered.
• the desired amount of acid used will also depend on the desired N- alkylchitosan concentration in the solution from which the film is cast. It will depend as well on the molecular weight and degree of deacetylation of the chitosan that was alkylated, since those properties determine the molar concentration of alkylamino groups available to react with the acid.
• about one acid equivalent is added per equivalent of the amine nitrogens in the N-alkylchitosan.
• N-alkylchitosan in the solution will vary depending on how the solution is to be applied, and also on the molecular weight of the N-alkylchitosan, as a lower concentration may be desired for a relatively high molecular weight N-alkylchitosan.
• Different application methods work best with solutions of different viscosities, but typically, the solution will contain from about 0.1 to about 15 wt% N- alkylchitosan, based on the total combined weight of the solution and the N-alkylchitosan.
• the N-alkylchitosan solution from which the film is prepared may include organic polymers, including without limitation, natural polymers such as starch or cellulose or even the unalkylated chitosan itself, and synthetic polymers such as polyurethanes, polyamides, and polyesters. Such polymers may be soluble or insoluble in the N-alkylchitosan solution.
• organic polymers including without limitation, natural polymers such as starch or cellulose or even the unalkylated chitosan itself, and synthetic polymers such as polyurethanes, polyamides, and polyesters.
• Such polymers may be soluble or insoluble in the N-alkylchitosan solution.
• a polyamide may be dissolved in a solution of N- alkylchitosan and formic acid, while a polyurethane suspension in water would remain a suspension when added to an N-alkylchitosan/acetic acid solution.
• a "composite film" of chitosan and N- methylchitosan i.e., a film cast from a solution of chitosan and N- methylchitosan, is much more flexible than either chitosan film or N- methylchitosan film.
• the N-alkylchitosan solution from which the film is prepared may include inorganic fillers, including without limitation, glass spheres, glass bubbles, clays (e.g., sepiolite, attapulgite, and montmohllonite), silica, alumina, titania, and the like. Small amounts of such fillers, preferably less than 10 wt%, can be used to increase thermal stability, modulus, and barrier properties of the N-alkylchitosan film where this is desirable.
• inorganic fillers including without limitation, glass spheres, glass bubbles, clays (e.g., sepiolite, attapulgite, and montmohllonite), silica, alumina, titania, and the like.
• small amounts of such fillers preferably less than 10 wt%, can be used to increase thermal stability, modulus, and barrier properties of the N-alkylchitosan film where this is desirable.
• the N-alkylchitosan solution from which the film is prepared may include additives such as flame retardants, plasticizers, stabilizers, tougheners, and the like, to enhance various properties of the N- alkylchitosan film such as strength, flexibility, fire resistance and dimensional stability.
• additives such as flame retardants, plasticizers, stabilizers, tougheners, and the like, to enhance various properties of the N- alkylchitosan film such as strength, flexibility, fire resistance and dimensional stability.
• flexibility of the film when wet can be enhanced by addition of ketoacids such as glyoxylic acid and levulinic acid.
• film insolubility can be obtained by adding sugars such as glucose and fructose to the N-alkylchitosan solution.
• Additives to an N-alkylchitosan solution may be soluble in the solution, or they may be present as dispersed insoluble material.
• Adding sugars, di- or multifunctional acids, or polyhydroxyl compounds can reduce the thermal requirements for rendering the N-alkylchitosan insoluble.
• annealing temperatures of about 100 0 C -120 0 C for about 1 to 10 minutes cause insolubility.
• the additives are present at less than 50% by weight, based on the total combined weight of N-alkylchitosan and additives.
• N-alkylchitosan film may be prepared by casting an N- alkylchitosan solution directly onto a substrate that will be incorporated along with the film into a laminate.
• the N-alkylchitosan solution may be cast onto a work device such as a smooth surface, such as glass or a polymer film (for example, polyester film). If the film is cast onto a work device, the film is then dried, detached and then incorporated into a laminate in a separate step.
• the solution may be applied to a substrate by any of a variety of methods known in the art. For a small scale process, such as a laboratory test sample, the solution is typically applied using a doctor knife.
• Methods available to coat surfaces which are planar and have irregular surfaces include without limitation spray coating, dip coating, and spin coating.
• the solution could be applied to, e.g., traveling web using methods that include without limitation reverse roll, wire-wound or Mayer rod, direct and offset gravure, slot die, blade, hot melt, curtain, knife over roll, extrusion, air knife, spray, rotary screen, multilayer slide, coextrusion, meniscus, comma and microgravure coating.
• These and other suitable methods are described by Cohen and Gutoff in "Coating Processes” in the Kirk-Othmer Encyclopedia of Chemical Technology [John Wiley & Sons, 5 th edition (2004), Volume 7, Pages 1 -35].
• the method chosen will depend on several factors, such as the rheology of the solution to be applied, the desired wet film thickness, the speed of a substrate that is traveling, and the required coating accuracy as a percent of total thickness.
• the applied solution is then dried by any suitable method known in the art such as exposure to a hot air oven, air impingement drying, or radiative (e.g. infrared or microwave) drying (See, generally, Cohen and Gutoff, op. cit.).
• a hot air oven air impingement drying
• radiative (e.g. infrared or microwave) drying See, generally, Cohen and Gutoff, op. cit.
• the result of the drying at this stage is a continuous film. If the N-alkylchitosan is dissolved in an aqueous solution of a volatile acid, that is, an acid whose boiling point is less than about 200 0 C, exposure to ambient air may be sufficient for drying, and drying will remove acid as well as water.
• a film at this stage is water-soluble, it can be made water- insoluble by heating; by reacting it with a crosslinking reagent; by treatment with a strong base; or by a combination of two or more of these methods.
• a film cast from a formic acid solution can be made water-insoluble by heat treatment after the film has been formed and dried, for example, by heating at about 100° to about 260 0 C for about 0.1 to about 60 minutes, or more preferably about 100 0 C to 180°C for about 1 to 10 minutes.
• Heat treatment plus the use of a crosslinking agent could also be used to render the N-alkylchitosan film insoluble.
• the film can also be made insoluble by adding any of a variety of crosslinking agents to a solution before a film is cast therefrom.
• a crosslinking agent is a reactive additive that creates bonds, i.e. crosslinks, between polymer chains.
• crosslinking agents for N- alkylchitosan include without limitation glutaraldehyde (X. Peng et al., Carbohydrate Polymers 65 (2006) 288-295), epichlorohydhn, and di-, and tri-carboxylic acids including succinic, malic, tartaric, and citric acids.
• Diacids such as adipic acid or other multifunctional acids such as levulinic acid, glyoxylic acid or halogenated organic acids, can be used to make the N-alkylchitosan solution. With these additives, temperatures of about 100 0 C -120 °C for about 1 to 10 minutes can cause insolubility.
• Crosslinking agents may also be applied to the film after it is dried.
• the film can also be made water-insoluble by contacting the film with a base and then washing, which converts the film from the N- alkylchitosan salt form to N-alkylchitosan.
• a base e.g., its reactivity toward base
• processing conditions e.g., temperature and contact time, continuous versus batch process.
• the base is a 1 % to 10% by weight aqueous solution of sodium hydroxide, and typical contact times are 30 seconds to 3 hours at ambient temperature. Heat treatment plus contact with base could also be used to render the film insoluble.
• an N-alkylchitosan film 1 may be prepared by casting an N- alkylchitosan solution directly onto a substrate 2 that will be incorporated along with the film into a laminate. It can also be cast on a work surface like PET film and coated with an additional layer or layers before or after the work surface is removed and discarded.
• the substrate onto which an N-alkylchitosan film may be prepared may itself be a continuous sheet or film, provided that the permeability of the substrate to water vapor under use conditions is adequate for the particular end use. For example, a garment would require much higher water vapor permeability than a tent or tarpaulin.
• a suitable substrate will have at least one surface that is smooth, i.e., essentially without protrusions above the plane of the substrate that are higher than the desired thickness of the coating of N-alkylchitosan that will be transformed into the film.
• a smoother substrate surface is required when the desired thickness of the coating of N-alkylchitosan is 25 microns than when it is 100 microns.
• a suitable substrate may be, for example, a film, a sheet whose permeability to water vapor under use conditions is adequate for the particular end use, a microporous membrane (i.e., one in which the typical pore size is about 0.1 to 10 micrometers in diameter), or an article prepared from any of the foregoing. It is preferred that the substrate surface that will be in contact with the N-alkylchitosan film be both smooth and nonporous.
• Suitable substrate materials include polar polymer films, including elastomers, glassy polymers, and semi-crystalline materials. A polar polymer has both dispersion and dipole-dipole forces, while a non- polar polymer has only dispersive attractive forces.
• Polar polymers generally contain a substantial fraction of oxygen and nitrogen containing groups, while non-polar polymers contain a substantial fraction of hydrocarbon or fluorocarbon with minimal oxygen and nitrogen containing groups.
• the N-alkylchitosan solution will wet non-polar surfaces if a surface active agent is added to the N-alkylchitosan solution.
• surface active agents are N-dodecylpyhdinium salts or ethylene oxide/propylene oxide block copolymers.
• the surfaces of non- polar films can be made polar by treatment with corona discharge in air.
• suitable substrate materials include without limitation Nafion® perfluorosulfonic acid tetrafluoroethylene copolymer(available from E. I. du Pont de Nemours and Company, Wilmington, Delaware,
• polyurethanes e.g., polyurethane films available from Omniflex Co., Greenfield , Massachusetts, USA
• polyether block polyamide copolymers e.g., Pebax® polyether block amides available from Arkema, Paris, France
• polyether block polyester copolymers e.g., sulfonated styrene- polyolefin di- and tri-block copolymers, and polyvinyl alcohol homopolymers and copolymers.
• the protective laminates described herein comprise a continuous N-alkylchitosan film and at least one layer of fabric.
• additional layers for example, a second fabric layer or a microporous membrane
• a laminate and potentially thus a composite structure thereof, that has features in addition to those offered only by the N-alkylchitosan film and the at least one fabric layer, and/or (c) improving the performance of the final structure.
• additional films or microporous membranes may be applied to the outer surfaces of the N-alkylchitosan film and, where present, the substrate, as shown in Figure 1 (3, 3') by coating, thermal lamination, and other means known in the art, to protect the N- alkylchitosan and substrate films from dust and liquids or physical damage.
• One or more layers of ballistic fabrics can be used to absorb the impact of a projectile and protect the wearer from harm.
• the continuous N- alkylchitosan film (and its associated substrate, where present) is incorporated into a structure that includes an outer layer of material (an "outer shell,” 5 in Figure 1 ) which is exposed to the environment and/or an inner liner 4.
• the outer and inner materials may each be chosen for functional reasons such as ruggedness, ballistic resistance, and resistance to abrasion or tearing, as well as to impart a comfortable feel and a fashionable appearance to apparel. Colored and patterned materials may also be used as outer layers to introduce camouflage features in military applications.
• the outer shell and inner liner materials are typically fabric or microporous membranes. Fabrics may be wovens or nonwovens ⁇ e.g., nonwoven sheet structures created by spun bonded/melt blown processes or by electrospinning as described in, e.g., Z. -M. Huang et al., Composites Science and Technology (2003), 63, 2223-2253). Fabrics may be prepared from any synthetic or natural fiber appropriate for the specific end use in mind.
• Preferred fabrics may be prepared from aramids, nylons, polyesters, cotton, and blends comprising any of these, such as, but not limited to blends of nylon and cotton fibers ("NYCO").
• nylon as used herein refers to polyamides other than aramids.
• An aramid is an aromatic polyamide, wherein at least 85% of the amide (-CONH-) linkages are attached directly to two aromatic rings.
• Flame retardant fibers, including other aramids may be blended with an aramid to impact fabric thermal performance and comfort.
• a suitable aramid may be in the form of a copolymer that may have as much as 10 percent of other diamine(s) substituted for the diamine of the aramid or as much as 10 percent of other diacid chloride(s) substituted for the diacid chloride of the aramid.
• the fabric is a p- aramid.
• the p-aramid is poly (p-phenylene terephthalamide) (PPD-T).
• M-aramids may also find use in the present invention, and in some embodiments the m-aramid is poly (m-phenylene isophthalamide) (MPD-I).
• P-aramid and m-aramid fibers and yarns particularly suitable for use in the present invention are those sold respectively under the trademarks Kevlar® and Nomex® (E. I. du Pont de Nemours and Company, Wilmington Delaware, USA), and Teijinconex®, Twaron® and Technora® (Teijin Ltd., Osaka, Japan), and equivalent products offered by others.
• the aramid fabric would be used in the outer shell, and the inner liner would more likely contain fabric such as polyester, nylon, cotton, or blends thereof, though m-aramids may be utilized as part of the inner liner as well to improve fire resistance
• Films and microporous membranes may be prepared from any synthetic or natural material appropriate for the specific end use in mind.
• films and microporous membranes that can be used as a component of inner liners or outer shells include without limitation expanded poly(tetrafluoroethylene) membranes such as those sold under the trademark GORE-TEX® (W. L. Gore & Associates, Inc., Newark, Delaware, USA); hydrophobic polyurethane microporous membranes (see, e.g., S. Brzezi ⁇ ski et al., Fibres & Textiles in Eastern Europe, January/December 2005, 13(6), 53-58); microporous (poly)propylene available from ,e.g., 3M (St.
• thermoplastic polyurethane such as those sold under the trademark Transport ® Brand Film by Omniflex (Greenfield, Massachusetts, USA); Pebax® polyether block amide by Arkema (Paris, France); and DuPontTM Active Layer, a polyester film available from E. I. du Pont de Nemours and Company (Wilmington, Delaware, USA).
• the selectively permeable laminates described herein can be assembled using any of the any of the sewing, stitching, stapling or adhering operations, such as thermally pressing, known in the art.
• the layers to be assembled include the N- alkylchitosan film 1 and at least one other layer.
• the N- alkylchitosan film is cast on a work device, the film is then dried and detached as a free-standing film.
• Other layers could be added either before or after detachment from the work device. It may then be attached to another layer (for example, substrate (2), outer shell (5), inner liner (4)) using an adhesive (for example, (6, 6') in Figure 1 ) such as a polyurethane-based adhesive.
• the adhesive may be present as a continuous layer, an array of adhesive dots, or in a number of alternative patterns such as lines or curves.
• the adhesive may be applied in a variety of ways including spraying or gravure roll.
• the laminate may be sandwiched between (additional) woven fabrics. Bonding between the film structure and the fabrics may be continuous or semicontinuous, for example, with adhesive dots or films. Alternatively, the bonding may be discontinuous, for example by sewing the edges together, an arrangement often referred to as a "hung liner". Other means of discontinuous bonding may include the use of Velcro® strips or zippers.
• the laminate, as well as the continuous N-alkylchitosan film itself, is selectively permeable, having a Moisture Vapor Transport Rate ("MVTR") of at least 2 kg/m 2 /24 h, while the transport rate of materials harmful to human health is low enough to prevent the occurrence of injury, illness or death.
• MVTR Moisture Vapor Transport Rate
• the specific transport rate needed will necessarily depend on the specific harmful material; for example, NFPA 1994, 2006 Revision requires ⁇ 4.0 ⁇ g/cm 2 one hour cumulative permeation for mustard and ⁇ 1.25 ⁇ g/cm 2 for Soman, both of which requirements are met by the laminates and the continuous N-alkylchitosan film it contains.
• the laminates, as well as the continuous N-alkylchitosan film itself can be used for the fabrication of, or as a component in, a variety of articles of manufacture, including articles of protective apparel, especially for clothing, garments or other items intended to protect the wearer or user against harm or injury as caused by exposure to toxic chemical and/or biological agents, including without limitation those agents potentially used in a warfighter environment and materials identified as "Toxic Industrial Chemicals” (TICs) or “Toxic Industrial Materials” (TIMs); see, for example, Guide for the Selection of Chemical and Biological Decontamination Equipment for Emergency First Responders, NIJ Guide 103-00, Volume I, published by the National Institute of Justice, U.S. Department of Justice (October 2001 ), herein incorporated by reference.
• TICs Toxic Industrial Chemicals
• TIMs Toxic Industrial Materials
• a TIC is an industrial chemical that has an LCt 50 value (lethal concentration of a chemical vapor or aerosol for 50% of the population multiplied by exposure time) less than 100000 mg/min-m 3 in any mammalian species and is produced in quantities exceeding 30 tons per year at one production facility.
• LCt 50 value lethal concentration of a chemical vapor or aerosol for 50% of the population multiplied by exposure time
• a few examples of TICs are phosgene, chlorine, parathion, and acrylonithle.
• Permeability of the laminate or a layer in the laminate to specific substances may be determined by various methods including, without limitation, those described in ASTM F739-91 , "Standard Test Method for Resistance of Protective Clothing Materials to Permeation by Liquids or Gases Under Conditions of Continuous Contact.”
• the item of apparel is useful to protect military personnel against dermal exposure to chemical and biological agents potentially encountered in a warfighter environment.
• agents include without limitation nerve agents, vesicant agents, tear gases (riot control agents), and human pathogens.
• nerves agents include without limitation: Sarin ("GB,” O-isopropyl methylphosphonofluoridate), Soman ("GD,” O-Pinacolyl methylphosphonofluoridate), Tabun (“GA,” O-Ethyl N 1 N- dimethylphosphoramidocyanidate), and VX (O-Ethyl S-2- diisopropylaminoethyl methylphosphonothiolate).
• vesicant agents include without limitation: sulfur mustards (e.g., Bis(2- chloroethyl)sulfide and Bis(2-chloroethylthio)methane), Lewisites (such as 2-chlorovinyldichloroarsine),and nitrogen mustards (such as Bis-(2- chloroethyl) ethylamine (“HN1 ”)).
• sulfur mustards e.g., Bis(2- chloroethyl)sulfide and Bis(2-chloroethylthio)methane
• Lewisites such as 2-chlorovinyldichloroarsine
• nitrogen mustards such as Bis-(2- chloroethyl) ethylamine (“HN1 ”).
• tear gases include without limitation: pepper spray (various capsaicinoids), Bromobenzyl cyanide ("CA”), Phenylacyl chloride (“CN”), o-Chlorobenzylidene malononitrile
• human pathogens include without limitation: viruses (e.g., encephalitis viruses, Ebola virus), bacteria (e.g., Rickettsia hckettsii, Bacillus anthracis, Clostridium botulinum), and toxins (e.g., Ricin, Cholera toxin, Anthrax toxin).
• viruses e.g., encephalitis viruses, Ebola virus
• bacteria e.g., Rickettsia hckettsii, Bacillus anthracis, Clostridium botulinum
• toxins e.g., Ricin, Cholera toxin, Anthrax toxin.
• a human pathogen is an agent, especially a microorganism that causes disease in humans.
• the item of apparel is useful to protect first responder personnel from known or unknown chemical or biological agents potentially encountered in an emergency response situation.
• the item is intended to protect cleanup personnel from chemical or biological agents during a hazmat response situation.
• hazardous material in addition to those listed above include certain pesticides, particularly organophosphate pesticides.
• Such clothing, garments or other items include without limitation coveralls, protective suits, coats, jackets, limited-use protective garments, raingear, ski pants, gloves, socks, boots, shoe and boot covers, trousers, hoods, hats, masks and shirts.
• the laminates can be used to create a protective cover, such as a tarpaulin, or a collective shelter, such as a tent, to protect against chemical and/or biological warfare agents.
• a protective cover such as a tarpaulin
• a collective shelter such as a tent
• the laminates can be used in various medical applications as protection against toxic chemical and/or biological agents.
• the laminates could be used to construct items of apparel for health care workers, such as medical or surgical gowns, gloves, slippers, shoe or boot covers, and head coverings.
• the chitosan material used in the following Examples was ChitoClear® TM-656, obtained from Primex Ingredients ASA, Norway under the trademark ChitoClear® chitosan, as noted. According to the manufacturer, Primex ChitoClear® TM-656 has a Brookfield viscosity of 26 cP (0.026 Pa » s, 1 % chitosan in a 1 % aqueous acetic acid solution). The M n and M w were determined by SEC to be 33,000 and 78,000, respectively.
• the molecular weights of the chitosan samples are determined by size exclusion chromatography using a triple-detector aqueous system, consisting of a Waters 2690 separations module, a Wyatt-DAWN DSP multi-angular (18) light scattering detector, a Waters 410 differential refractometer (Waters Corporation, Milford, Massachusetts, USA), and a Viscotek T60-B viscometer (Viscotek, Houston, Texas, USA). Two TSK- GEL GMPW columns (TOSOH Bioscience LLC, TOSOH Corporation, Tokyo, Japan) are used.
• the mobile phase is an aqueous solution of 0.3M acetic acid with 0.3M sodium acetate at a flow rate of 0.5 mL/min.
• the samples have been first dissolved for 4 hours in a shaker.
• Moisture Vapor Transmission Rate This was measured by a method derived from the Inverted Cup method of MVTR measurement [ASTM E 96 Procedure BW, Standard Test Methods for Water Vapor Transmission of Fabrics (ASTM 1999)]: A vessel with an opening on top is charged with water and then the opening is covered first with a moisture vapor permeable (liquid impermeable) layer of expanded-PTFE film (“ePTFE”), and then with the sample for which the MVTR is to be measured, and finally by woven fabric overlayer [NYCO 50:50 nylon/cotton blend, 6.7 oz/yd 2 (0.23 kg/m 2 ) or Nomex® fabric, 5.6 oz/yd 2 (0.19 kg/m 2 ), both treated with durable water repellant finish].
• ePTFE expanded-PTFE film
• the three layers are sealed in place thereby forming a laminate, inverted for 30 minutes to condition the layers, weighed to the nearest 0.001 g, and then contacted with a dry stream of nitrogen while inverted. After the specified time, the sample is re-weighed and the MVTR calculated (kg/m 2 /24 h) by means of the following equation:
• MVTR 1/[(1/MVTRobs.) - (1/MVTR mb )] where MVTR O bs is observed MVTR of the experiment and MVTR mb is the MVTR of the ePTFE moisture barrier (measured separately). The reported values are the average of results from four replicate samples.
• DMMP Dimethylmethylphosphonate
• DMMP is used as a relatively non-toxic simulant for chemical warfare G-class nerve agents.
• the DMMP permeation for the examples described below was carried out as follows: A vessel with an opening on top was charged with a measured amount of water containing 0.100% propylene glycol as an internal GC standard. If the sample was a film, the opening was covered with the sample film and a woven fabric overlayer [NYCO 50:50 nylon/cotton blend, 6.7 oz/yd 2 (0.23 kg/m 2 ) or Nomex®, 5.6 oz/yd 2 (0.19 kg/m 2 ), both treated with durable water repellant finish] was placed on top of the film, and the layers were sealed in place thereby forming a laminate.
• the sample was a laminate that already had a fabric surface, no additional fabric overlayer was used.
• the fabric surface was treated with one 2 ⁇ l_ drop of DMMP (2.3 mg).
• the vessel was placed in a nitrogen-purged box for 17 h and then the DMMP concentration in the water was measured by GC analysis. Results are reported in ⁇ g of DMMP measured in the water after 17 h and are the average of five replicate samples.
• the DMMP was obtained from Aldrich Chemical Company (Milwaukee, Wisconsin, USA) and was used as received.
• the mixture was heated to 80 0 C then rotated on a roll mill until it cooled to room temperature. This heating and rotating was repeated three more times.
• the solid N-methylchitosan thereby produced was collected by filtration, washed with water, and dried.
• the solid was dissolved in 200 ml_ of water containing 2.76 g formic acid.
• the solution was pressure filtered through coarse filter paper, degassed, cast onto a glass plate with a 25 mil (0.64 mm) box doctor knife, and dried at 100°C.
• the film was freed from the formate anion by soaking in 10% sodium hydroxide/water for 4 min at room temperature. The film peeled easily from the glass plate. It had the following properties:
• Example 2 illustrates the preparation and properties of an N- methylchitosan film using a different methylating mixture.
• the process of Example 1 was repeated except that the methylating mixture contained:
• the reaction mixture possessed a faint odor of methylamines.
• the solid N-methylchitosan was converted to film as described in Example 1 and had these properties:
• the chitosan was methylated to a higher degree by increasing the molar ratio of dimethyl sulfate to chitosan NH 2 groups from 1 :1 (Example 1 ) to 3:1 , and the film was subjected to various post- treatments.
• the reaction was carried out in a bottle as described in Example 1.
• the bottle was charged with:
• Section 1 was treated with 10% aqueous NaOH, washed with water, and dried.
• Section 2 was heated at 165°C for 5 min in an aluminum foil envelope under a nitrogen atmosphere.
• Section 3 was first subjected to the same heat treatment as Section 2, then treated with 10% aqueous NaOH, washed with water and dried, as for Section 1.
• Section 4 was prepared by heating a sample of Section 1 at 170 0 C for 5 min in an aluminum foil envelope under nitrogen.
• N-methylchitosan film shrinkage is lowered by incorporating a polyhydroxyalkyl compound.
• N-methylchitosan solution as the formate salt in water (prepared as in Example 1 ) was added 25 mg pentaerythritol. The mixture was rotated until the pentaerythritol had dissolved and then was cast onto a glass plate. The resulting film was placed on a 99°C press platen (no pressure) for 4 to 5 min, until just dried - no longer. The dry state was determined visually. The film was removed from the glass, placed in an aluminum foil envelope under nitrogen and heated at 104 0 C for 5 min. Its properties are presented in Table 2, in comparison with the N-methylchitosan film prepared in Example 1.
• Example 4 The procedure of Example 4 was repeated, except the pentaerythritol was replaced with 10 mg glucose. The resulting film was insoluble in aqueous formic acid and had these properties:
• EXAMPLE 6 This example demonstrates the preparation of a film from a solution of N-methylchitosan and chitosan. This composite film had remarkable resistance to tearing, a property that neither component possessed by itself.
• a 1 :1 by weight film of N-methylchitosan and chitosan was prepared by first mixing
• an apparatus or method is stated or described herein as comprising, including, containing, having, being composed of or being constituted by certain components or steps, it is to be understood, unless the statement or description explicitly provides to the contrary, that one or more components or steps other than those explicitly stated or described may be present in the apparatus or method.
• an embodiment of an apparatus or method of this invention may be stated or described as consisting essentially of certain components or steps, indicating the absence of components or steps that would materially alter the principle of operation or the distinguishing characteristics of the apparatus or method. Further, if an apparatus or method is stated as consisting of certain components or steps, components or steps other than those as stated or described are not present therein.
• indefinite article “a” or “an” is used with respect to a statement or description of the presence of a component in an apparatus, or a step in a method, of this invention, it is to be understood, unless the statement or description explicitly provides to the contrary, that the use of such indefinite article does not limit the presence of the component in the apparatus, or of the step in the method, to one in number.

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