A composition for the promotion of adhesion between a rubber formulation and a textile substrate is provided. The inventive composition comprises either a mixture of specific amine functional silanes and organo-functional silanes having reactive groups or groups with an affinity for rubber. The inventive method entails the use of the inventive composition or a silane compound having both an amine moiety and a reactive group having an affinity for rubber formulations, particularly an unsaturated carbon-carbon bond. The composition may be utilized to adhere any standard reinforcement-type textile, such as polyester or polyamide, to a standard rubber composition, such as SBR, NBR, or EPDM. A method for adhering textiles to rubber formulations is also provided involving a pre-dip, -spray, -coat, and the like, of the inventive composition on a reinforcement-type textile surface followed by the contacting of the rubber formulation. Optionally, and preferably, the process involves the extra utilization of resorcinol-formaldehyde latex as an effective bonding agent to improve the adhesion between the two layers. The resulting textile-reinforced rubber product may be utilized as an automobile fan or timing belt, an automobile tire component, and any other rubber article which requires long-lasting, durable textile reinforcement.

This invention relates to adhesion promotion compositions which provide excellent adhesive characteristics between rubber and textile substrates. Such compositions comprise specific mixtures of aminosilanes and other organosilanes or specific compounds having both an aminosilane moiety and a group having an affinity for rubber compositions. These inventive compositions may be utilized to activate a textile surface for further contact with a rubber alone or a resorcinol-formaldehyde latex (RFL) or similar type of adhesive compound to which a rubber may subsequently be adhered. The methods utilizing these particular adhesion promotion compositions are also contemplated within this invention.
It has long been known that adhering a textile, particularly one composed of filaments having high tenacity to a rubber enhances the modulus and tensile strength of the rubber component and provides long-lasting durability, particularly in high friction applications. Examples of such applications include fan and timing belts within automobile engines; vehicle tires; conveyor belts; and the like. The main requirement of such textile-reinforced rubber articles has been the strength of adhesion between the textile and the rubber. Without any primer treatment, the textile will not effectively adhere to the rubber. A weak bond between the two components results in separation of the two layers and mechanical failure of the resulting composite. Thus, it has been and is necessary to provide a textile treatment to enhance the adhesion of these two distinct components.
Previous methods of providing such adherence between rubber and textile layers include coating or impregnating the textile layer with a formaldehyde latex (such as a resorcinol-formaldehyde vinyl-pyridine rubber latex or RFL), pre-coating with an RFL latex and an amino functional polyacrylate, as in U.S. Pat. No. 5,654,099, to Pelton, and in European Patent Application 665,390, to Tsubakimoto Chain Company, or utilizing a pre-activated textile which has reactive pendant groups to facilitate adhesion between the fabric surface and the reactive sites on the rubber layer, all of the aforementioned references being herein entirely incorporated by reference. The RFL coating method results in a composition which does not always provide sufficient adhesion between layers. Pre-activated textiles, such as a polyester fibers coated with an epoxy adhesion enhancer, are typically used in combination with an RFL treatment to further improve the textile adhesion to rubbers. Although such pre-activated textiles perform well in many cases, there remains a need for less expensive methods and compositions for adhesion promotion between rubber and textile layers in order ultimately to produce a reinforced, long-lasting, and durable rubber product.
Also worth mentioning are U.S. Pat. No. 5,064,876, to Hamada et al., and U.S. Pat. No. 5,082,738, to Swofford, both of which teach a primer composition for promoting adhesion for polymer films. Such disclosed compositions comprise aminofunctional silanes. However, neither of these references teach the application of textiles to rubber formulations for reinforcement purposes nor do they teach or fairly suggest the necessary combination of an amine functional group and another organo-functional group, in particular a reactive group having an affinity for rubber, as is now required within the inventive composition and method.
It is thus an object of the invention to provide improved adhesion for a long-lasting and durable textile-reinforced rubber product. A further object of the invention is to provide a relatively inexpensive method of achieved such improved adhesion. Another object of the invention is to provide an adhesion promoter which ultimately provides a textile-reinforced rubber product which does not exhibit adhesive failure. Yet another object of this invention is to provide a stable aqueous primer composition that, when applied before an RFL treatment, activates the textile substrate in order to provide greatly improved adhesion to various rubber compounds.
Accordingly, this invention concerns a composition for promoting the adhesion between a rubber composition layer and a textile reinforcing layer comprising
a mixture of at least two different silane compounds, at least one compound selected from (I) and at least one compound selected from (II); wherein (I) and (II) include the following:
(I) aminosilanes selected from the group consisting of
xe2x80x83wherein R is C1-C6 alkyl, R2 is an amine functional group, and Rxe2x80x2 is an alkyl- or aromatic-acyl group;
(II) organo-functional silanes selected from the group consisting of
xe2x80x83wherein R2 is a group containing a radical selected from the group consisting of a mercapto moiety, a sulfide moiety, an isocyanate moiety, an epoxy moiety, a pyridine moiety, a hydrophobic saturated alkyl moiety, and a moiety having at least one unsaturated carbon-carbon bond, and R and Rxe2x80x2 are defined as for (I) above. Nowhere within the prior art has such a specific adhesion promotor composition been disclosed or practiced, particularly for activating textile substrates in order to improve adhesion to rubbers. Furthermore, nor has such a specific composition or method of utilizing such a composition been taught or fairly suggested. Such compositions and methods provide significant advantages over the standard adhesion compositions and methods of the state of the art.
Also, it has been discovered that a stable aqueous dispersion of the composition (a) above can be obtained without the use of any dispersing agents or surfactants. Component (II) of the inventive composition is not water soluble (some of the covered compounds can even react with water and thus are not stable in aqueous solution). Although a water dispersion of the component (II) can be produced utilizing surfactants, such dispersions have very limited shelf life. Besides, the surfactants necessary to make such dispersions tend to affect adhesion adversely since surfactants are known to migrate to the interfaces and interfere with the microscopic intimate contact between two uniting materials. However, by mixing components (I) and (II) together, then slowly adding water to the mixture, a stable aqueous dispersion/solution can be obtained without utilizing any potentially deleterious surfactants or dispersing agents.
The relative cost of the inventive compositions is very low at the preferred level of usage, particularly when compared with the pre-activated textiles mentioned above. All of these characteristics and improvements with the inventive compositions and methods thus translate into lower costs for the user. Additionally, the inventive compositions and methods can be utilized with any rubber compositions and with any type of smooth filament textile normally utilized as a rubber reinforcement material. Examples of rubber compositions include, and are not limited to, natural rubber, polyurethane rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubbers, fluorinated rubbers, and ethylene-propylene-diene rubber (EPDM). Modified rubbers which are potentially useful, though more expensive, include hydrogenated SBR, hydrogenated NBR, and carboxylated NBR. Suitable textiles include, and are not limited to, those comprising polyester, polyester/cotton blends, polyamides, such as nylon-6 or -6,6, polyaramids (such as Kevlar(copyright), available from DuPont), polypropylene, boron derivatives, glass fibers, and carbon fibers. The textile component may be dyed or colored various shades and hues in order to facilitate categorizing the different widths, lengths, etc., of products such as, without limitation, timing belts, and the like, for automobiles. Finally, the inventive compositions and methods, when utilized and/or practiced as intended, result in a textile-reinforced rubber product which does not exhibit textile/rubber adhesive failure.
Preferably, the inventive composition comprises (I) an amine-functional silane component and (II) an organo-functional silane component, which includes an unsaturated carbon-carbon bond. As noted above, other reactive groups may be employed on the organo-functional silane component, such as, isocyanates, mercaptos, and epoxies, only as examples. Being alkoxysilanes, also, both components (I) and (II) hydrolyze in the presence of water, then couple with either each other and each with itself to form oligomers. It is therefore expected that pre-hydrolyzed silane products can be utilized as substitutes for components (I) and (II). Obviously some of the organic functional group in component (II) will react with the amine group in component (I) upon mixing. However, it is the mixture of these two components that generates the unexpected synergistic adhesion improvement which cannot be achieved practically with either component alone.
Preferably, the inventive composition comprises a mixture of two separate compounds, an amine-functional silane (I) having the following structure:
R1xe2x80x94Si(OR)3xe2x80x83xe2x80x83(I)
wherein R is C1-C6 alkyl and R1 is an amine-functional group having the molecular structure of
(NH2R)(NHR)yxe2x80x94Si(OR)3
wherein R is defined for (I) as in claim 1 and y is 0-4, and an organo-functional silane (II) having the following structure:
R2xe2x80x94Si(OR)3xe2x80x83xe2x80x83(II)
wherein R is C1-C6 alkyl and R2 is a group having an unsaturated carbon-carbon bond. Of particular preference are (I) aminoethylaminopropyltrimethoxysilane, available from Dow Corning, Midland, Mich., and (II) 3-methacryloxypropyltrimethoxysilane, also available from Dow Corning. These particular compounds provide the best adhesion promotion between textile substrates and rubber compositions for the lowest cost. Also, the amount of (I) and (II) is measured in weight ratios, with the preferred range being from about 1:1 [(I) to (II)] to about 100:1. Most preferred is a weight ratio of from about 2:1 to about 10:1. The inventive composition may be present in a dispersion, either aqueous or non-aqueous, or in a neat solution diluted with an organic solvent. An aqueous dispersion without any surfactants added is preferred, as noted previously. The preferred concentration of silanes is from about 0.1 to about 5% on the weight of the fabric (owf) with a preferred range being from about 0.5 to about 2% owf. Furthermore, it is preferred that, after the application of the inventive composition, a RFL treatment be used to increase the adhesive qualities of the entire product.
Any standard rubber additives, including ultraviolet absorbers, antioxidants, dyes, colorants, curing agents, perfumes, antistatic agents, fillers (such as carbon black), and the like may be added to the rubber. To the textile substrate may be added any other standard textile additives, such as dyes, colorants, pigments, ultra violet absorbers, antioxidants, and wetting agents. To the inventive composition and RFL used in combination with the inventive composition may be added wetting agents, antioxidants, filler dispersion (such as carbon black, silica and ZnO dispersions).
The preferred inventive method of producing a textile-reinforced rubber composite comprises the sequential steps of
(a) providing a textile substrate;
(b) contacting the textile substrate with a composition comprising either
(i) a mixture of at least two different silane compounds, one compound selected from (I) and the other selected from (II); wherein (I) and (II) include the following:
(I) amine-functional silanes selected from the group consisting of
xe2x80x83wherein R is C1-C6 alkyl, R1 is an amine-containing functional group, and Rxe2x80x2 is an alkyl- or aromatic-acyl group;
(II) organo-functional silanes selected from the group consisting of
xe2x80x83wherein R is C1-C6 alkyl, R2 is a group containing a radical selected from the group consisting of a mercapto moiety, a sulfide moiety, an isocyanate moiety, an epoxy moiety, a pyridine moiety, a hydrophobic saturated alkyl moiety, and a moiety having at least one unsaturated carbon-carbon bond, and Rxe2x80x2 is the same as defined for (I) above; or
(ii) at least one functional silane containing both an amine-functional group and a moiety having an affinity for rubber (such as an unsaturated carbon-carbon bond);
(c) heating the textile substrate at a temperature of from about 120 to about 250xc2x0 C. for from about 15 seconds to about 5 minutes, preferably about 3 minutes;
(d) optionally coating or impregnating the textile substrate with an RFL composition;
(e) combining at least a portion of the resulting treated textile substrate with a rubber formulation to from a textile-reinforced rubber composite; and
(f) curing the textile-reinforced rubber composite.
In this process, contacting step (b) may be performed by any standard, well known method, including dipping, padding, spraying, coating, impregnating, and the like. This silane pre-treatment of the textile in essence xe2x80x9cactivatesxe2x80x9d the fibrous surface by effectively coating the textile with the adhesion promoter having reactive groups and groups having affinity for the rubber layer oriented in a position to facilitate the subsequent contact and adhesion of the rubber layer with the textile layer. One of ordinary skill in the art would understand and be familiar with the addition and contacting of the subject textile and rubber formulation with the potentially preferred RFL latex component as well as the rubber formulation contacting step (e), above. Furthermore, curing step (f) is performed in any conventional manner, such as through heat-activated vulcanization in the presence of a curing agent (such as organic peroxide). Again, such a step should be well within the purview of the ordinarily skilled artisan in this field.
The Examples below are indicative of the particularly preferred embodiment within the scope of the present invention:

High peel strength rubber/textile composites


A method for producing a one-piece cast vehicle wheel, the wheel having at least one hub portion connected to a wheel rim via at least one spoke oriented in the radial direction of the wheel, in which at least one lost core is inserted in a molding of the casting machine, the one-piece vehicle wheel is cast, and the lost core is removed from the cast vehicle wheel and thereby forms at least one opening in the spoke. A one-piece cast vehicle wheel formed by the method is also provided.

The invention relates to a method for producing a cast vehicle wheel and to a vehicle wheel.
Reference is made by way of example to German patent documents DE 10 2007 046 124 B4, DE 199 26 575 C2 and DE 41 38 558 C2.
Wheels of vehicles, in particular wheels of passenger vehicles, are subject to a very wide variety of requirements. In addition to sufficient strength at a low weight, the wheels are intended to be favorable for a good coefficient of air resistance of the vehicle and to be distinguished by a pleasing visual appearance.
A wheel known from the prior art customarily comprises a hub section and a rim section, wherein these two sections are customarily connected to one another by a plurality of spokes.
Different variants for reducing the weight of the spokes or the spoke bodies of cast vehicle wheels and thus for reducing the unsprung masses are known from the prior art. In contrast to forged vehicle wheels, cast vehicle wheels are customarily more solid because of being less strong, and therefore they are generally heavier.
DE 10 2007 046 124 B4 describes a cast vehicle wheel in which a hollow body is integrated as a mold core in the spoke during the casting process. A disadvantage of this, however, is that such a mold core always remains in the vehicle wheel after the casting process and a sufficiently strong connection between the mold core and the material of the wheel can be realized only with difficulty. In addition, such mold cores are complicated to produce.
By contrast, one or more cast spokes of a wheel that are hollow are known from DE 199 26 575 C2 and DE 41 38 558 C2. For this purpose, a lost core is placed into the casting mold of the spokes during the casting process. The lost core is removed from the spoke after the casting process and the then hollow spoke is connected after the casting process to the hub or to the rim.
However, such an embodiment has the disadvantage that the spoke has to be connected retrospectively to the hub or to the rim of the wheel. The production process of the wheel is therefore long and costly.
It is the object of the invention to specify a method for producing a vehicle wheel, which method can be carried out cost-effectively and simply and at the same time provides a vehicle wheel which is reduced in weight and is optimized in respect of rigidity and strength.
The object is achieved by a method for producing a cast vehicle wheel in which at least one lost core is inserted into a molding of the casting machine, the one-piece vehicle wheel is cast, the lost core is removed from the cast vehicle wheel, and after removal of the lost core the vehicle wheel includes at least one opening in at least one spoke. The object is further achieved in the form of a vehicle wheel formed with a lost core using the method of the present invention. Advantageous embodiments and developments are the content of the dependent claims.
The vehicle wheel (also referred to for short as wheel), for its part, is accordingly produced in a casting method, in particular in a diecasting method. The vehicle wheel here is formed in particular from a cast aluminum material or a cast steel material or of an alloy of these materials.
In the casting process, the vehicle wheel is produced from liquid metal (for example aluminum or steel or a suitable alloy) which is also referred to as the melt. Use is made here in particular of what is referred to as dead mold casting, in which the melt is poured into a hollow mold in which it subsequently solidifies. In the diecasting method, for example, an upper die or mold and a lower die or mold compresses the liquid melt in its desired shape until it solidifies. The inner surface of this hollow mold or die is the negative of the outer surface of the casting.
The (ready cast) vehicle wheel comprises a hub section which is connected to an annular rim via at least one radially running spoke. Preferably, a plurality of spokes are provided which are adjacent to one another and form at least one spoke intermediate space which is bounded by the spoke side surfaces oriented in the circumferential direction of the wheel and by the hub section and the rim.
During the production of such a vehicle wheel, it is provided, in a first step, before the actual casting process that at least one "lost core" is inserted into a molding, for example into a die mentioned, i.e. between the upper die and the lower die of the vehicle wheel to be cast.
Such a lost core is in particular a sand core. Alternatively or additionally, the lost core can also be in the form of a graphite core, a fireclay core, a clay or ceramic core, a glass core, a salt core, (compressed and pressed) carbon fibers or a mixture of the materials mentioned or further materials, which core can be removed from the wheel after the casting process of the vehicle wheel. The lost core is removed here by suitable methods.
The sand core mentioned is preferably used here since the latter also brings advantages in respect of the flow properties of the melt and the associated better solidification properties.
Preferably, such a lost core, in particular a sand core, is introduced into the molding by what is referred to as a core shooting method. In a core shooting machine, a basic mold material mixed with a binder is introduced into a core mold with a certain shooting pressure and possibly defined operating temperature. After the curing of the casting core produced in such a manner, the latter is preferably inserted into the casting mold. Following the casting which has taken place, the molding material from which the core has been produced is removed through the openings provided for this purpose in the casting structure.
It is particularly preferably provided here that a graphite material is used as a binder. A graphite sizing is thus arranged on the lost core, as a result of which the surface of the wheel solidified against the lost core is smoother and less rough.
Alternatively or additionally, it is also possible to produce the lost core or parts thereof by what is referred to as a 3D printing method. For example, one part of the core can be produced by the core shooting method mentioned, while another part of the core is produced by the 3D printing method. The individual parts can subsequently be connected by adhesive bonding (for example by means of a graphite material). For example, the lost core or parts thereof can be produced in a casting, punching, weaving or other 3D molding method.
It is furthermore possible here for a plurality of lost cores to be inserted into the molding.
Preferred geometrical forms of the lost core will be discussed in more detail further below.
In a next step of the method for producing the vehicle wheel, it is provided that the vehicle wheel is cast in one piece. Within the context of this invention, a one-piece wheel is a wheel which is produced completely, i.e. with a rim, with one or more spokes and with a hub section, as it were "in one casting" after the casting process or by the casting process. The individual wheel parts, for example the rim, the hub or the spokes, no longer have to be connected to one another retrospectively, but rather are already produced from one piece in the casting method.
After the casting process of the vehicle wheel, it is provided that the lost core, in particular the sand core, is removed from the cavity or space of the vehicle wheel by a suitable method. It is furthermore provided here that the lost core, after its removal, forms at least one opening in the at least one spoke.
Such an opening here is in particular a recess or an undercut or an undercut stamping or an aperture through the spoke. It is not envisaged producing a closed cavity in the spoke by removal of the lost core; instead, the spoke in the state ready for use (i.e. when the spoke is mounted on the vehicle and is ready for operation) always comprises the opening mentioned by means of removal of the lost core.
It is particularly preferably provided here that the opening mentioned is arranged on at least one spoke side surface of the spoke running at least approximately in the axial direction of the wheel. If a plurality of spokes are present, the spoke side surfaces can be described as the surface forming the abovementioned spoke intermediate space together with a hub section and a rim section. The spoke side surfaces are those surfaces of the spoke that are oriented in the circumferential direction of the wheel and are in each case opposite one another in a spoke intermediate space.
That is to say, it is preferably not the outer or inner spoke surface which is provided with the opening mentioned, but rather the spoke side surface. The opening is thus preferably provided in the circumferential direction in or on the spoke.
Particularly preferably, an aperture is produced in the circumferential direction through the spoke by removal of the lost core.
However, it is additionally possible also to form an opening or a recess on one or more spoke outer surfaces or spoke inner surfaces by means of the lost core or by removal thereof. Within the context of this invention, such a spoke outer surface is that surface of the spoke which, in the installed state of the vehicle wheel in the vehicle, faces away from the vehicle and is oriented at least approximately in the axial direction of the vehicle wheel. Within the context of this invention, a spoke inner surface means that surface of the vehicle wheel which, in the installed state of the vehicle wheel in the vehicle, faces the vehicle and is likewise at least approximately oriented in the axial direction of the vehicle wheel.
Furthermore, it is possible for the spoke to be machined or blasted (for example in a sandblasting method) or trowalized following the method of casting the vehicle wheel. All these methods serve, for example, to smooth the spoke surface that is roughened by the lost core, in particular the sand core. Furthermore, it is possible to remove excess material on the wheel or on the spoke or the spokes by subsequent machining.
Furthermore, it is preferably provided for there to be mechanical processing on a part of a spoke surface of the ready cast wheel, on which no opening is formed after removal of the lost core. It is thus possible, for example, that, by milling or drilling on that surface mentioned, an additional opening is produced which opens in the opening of the spoke, which opening is formed by the lost core. A skeleton structure of the spoke can thus be produced in an advantageous manner.
The method mentioned permits the production of a vehicle wheel with one or more spokes provided with apertures and openings. The opening or openings in the spoke or in the spokes of the wheel, such as, for example, the mentioned apertures, recesses and undercuts, permit a saving on material and at the same time an enlargement of the surface of the spokes and thus an increased rigidity and strength of the spoke and of the wheel itself. Furthermore, it is possible by the method mentioned to produce a vehicle wheel cost-effectively (in a casting method) and nevertheless to reproduce different geometries and designs of the spokes.
In addition to the method for producing the vehicle wheel, a vehicle wheel which is produced by the inventive method is claimed. As already mentioned further above, this vehicle wheel comprises a hub section which is connected to a rim of the wheel via at least one spoke which is oriented in the radial direction of the wheel. The at least one spoke here comprises an opening which is mentioned and which is produced on the spoke in a cost-effective and simple manner by the method according to the invention, in particular by removal of the lost core. Preferably, a plurality of spokes are provided which are adjacent to one another and form at least one spoke intermediate space which is bounded by the spoke side surfaces, which are oriented in the circumferential direction of the wheel, and by the hub section and the rim. This opening is produced here by the removal of the lost core mentioned.
As likewise mentioned further above, the opening can be an undercut, a recess or an aperture of the spoke.
The opening here is preferably provided on at least one spoke side surface.
It is thus particularly preferably provided that the opening is an aperture which runs in the circumferential direction of the spoke and separates or divides the spoke into an outer spoke part (facing the outside in the installed state of the wheel) and an inner spoke part (facing the vehicle in the installed state of the wheel in the vehicle). This aperture can extend, for example, over the (entire) length of the spoke (as viewed in the radial direction), as a result of which, in such a case, the spoke would be divided in two in the axial direction of the wheel.
However, it is additionally possible, as already mentioned above, also to form an opening or a recess on one or more spoke outer surfaces or spoke inner surfaces by means of the lost core or by its removal.
In order to realize such an opening in the spoke, in particular on one or on both spoke side surfaces, it is preferably provided that the lost core is in the shape of a section of a ring. It is thus possible for the lost core after the casting operation of the vehicle wheel to project through the at least one spoke in the circumferential direction of the vehicle wheel and to thus constitute an aperture mentioned (upon removal).
If a plurality of spokes are provided with the same opening in each case and the wheel is thus formed, for example, symmetrically, it is preferred that the lost core is a continuous ring or is annular, wherein the lost core is inserted into the molding or into the die in such a manner that the ring center point is positioned on the axial axis of the vehicle wheel.
In the case of a plurality of spokes which comprise an aperture or an opening, it is preferred that, after the casting process of the wheel (i.e. before the core is removed), the lost core is arranged in the spoke side surfaces in such a manner that it projects through a spoke or projects at least into two spoke intermediate spaces. Particularly preferably if the lost core is annular, this ring projects fully through all of the spokes at once.
In addition to such apertures, it is possible to provide rib-like or undulating structures or surfaces in the spoke interior or on the surfaces of the opening in the spoke. Such structures increase the surface of the spoke and, in addition to the rigidity and strength, also optimize the cooling properties of the vehicle wheel.
Furthermore, it is possible for the lost core to be formed in such a manner that the ready cast wheel has a fastening device or the like in the opening according to the invention after removal of the lost core. It is possible, for example, for a cover element for covering a spoke intermediate space of the spokes or for a wheel cap to be fastened to such a fastening device. Such a fastening device can be designed, for example, in the form of a latching lug, a notch or the like. For example, such a cover element can be hooked or clipped into the edge which arises by means of the additional opening mentioned between the opening formed by the removal of the core and the additional opening. The edge or the additional opening can also be in the form of a latching lug, a bore or a notch. Detailed embodiments can be gathered from the Figures.
These and further features emerge not only from the claims and the description but also from the drawings, wherein the individual features can be realized in each case by themselves or as a plurality in the form of subcombinations in an embodiment of the invention and can constitute advantageous and inherently protectable embodiments for which protection is claimed here.
The invention is explained in further detail below with reference to a plurality of exemplary embodiments. All of the features described in more detail may be essential to the invention.

Method for producing a cast vehicle wheel

Bayerische Motoren Werke Aktiengesellschaft


A data security method and apparatus that provides an exceptional degree of security at low computational cost. The data security arrangement differs from known data security measures in several fundamental aspects. Most notably, the content of the message is not sent with the encrypted data. Rather, the encrypted data consists of pointers to locations within a virtual matrix, a large (arbitrarily large), continuously-changing array of values. The encryption technique is therefore referred to as Virtual Matrix Encryption. Furthermore, the data security arrangement uses a very large key of one million bits or more which creates a level of security much higher than any other existing method. The key is not transferred but is instead created from a file of any size that is available on both a computer used to send a secure message and a computer used to receive a secure message. The term Virtual Key Cryptographic as used herein to refer to techniques in which a key is recreated at a remote location from an electronic file without any transmission of the key itself. The file may be a system file, a file downloaded from the Internet, etc. A smaller, transaction-specific key, e.g., a 2,048 bit key, is sent end-to-end and is used in conjunction with the very large key to avoid a security hazard in instances where the same file is used repeatedly to create the very large key.

1. Field of the Invention
The present invention relates to data security.
2. Description of the Related Art
Many different types of data security measures are known. Presently, most widespread data security measures are based on public-key encryption. Public-key encryption is described, for example, in U.S. Pat. No. 4,218,582, incorporated herein by reference. Other patents relating to public-key encryption include U.S. Pat. Nos. 4,200,770; 4,405,829; 4,424,414 and 4,995,082, all of which are incorporated herein by reference.
One of the reasons for the relative prominence of public-key cryptography is that it solves the problem of key distribution in an elegant fashion.
Prior to public-key cryptography, symmetric-key cryptography required use of the identical key to decrypt the file as was used to encrypt the file. Hence, the key had to be communicated in secrecy between users. In public-key encryption, the encryption and the decryption keys are separate, with the encryption key being publicly known and the decryption key being kept secret. Public-key encryption may also be used for authentication.
Despite the important advantage of not requiring secure key distribution, public-key cryptography also suffers from various disadvantages. Administration is typically required to ensure that unique public-keys are assigned to each user. A person's public-key must be listed in a directory, and must be found in the directory prior to encrypting a message. The computational burden of public-key cryptography is significant both in generating random prime numbers for use as keys and in encryption and decryption processing itself. Furthermore, despite the computational complexity, public-key encryption using medium size keys has been shown to be insecure given the tremendous network computing resources that may be brought to bear on breaking the encryption.
What is needed, then, is a data security mechanism that surpasses in security present public-key cryptography methods and that minimizes the computational burden involved.

Virtual matrix encryption (VME) and virtual key cryptographic method and apparatus


The present invention relates to the photocatalytic degradation of organic compounds by zeolite and/or mesoporous material hosted photocatalysts. The present invention further relates to a method of treating a contaminated aqueous liquid or gaseous fluid containing organics using a combination of visible or solar light energy in the presence of a photocatalyst to decompose the organic impurities in the liquid or gaseous fluid.

The present invention relates to the photocatalytic degradation of organic compounds by zeolite and/or mesoporous material hosted photocatalysts. The present invention further relates to a method of treating a contaminated aqueous liquid or gaseous fluid containing organics using a combination of visible or solar light energy in the presence of a photocatalyst to decompose the organic impurities in the liquid or gaseous fluid.
Contaminated water is becoming a growing problem in many areas of the world. It is desirable to be able to efficiently and effectively remove such contamination (e.g. halogenated organic materials) from aqueous liquids such as water containing chlorinated hydrocarbons, e.g., chlorinated phenols. Prior art removal techniques have included the use of ultraviolet light radiation to decompose halogenated organic compounds. For example, Chou et al., U.S. Pat. No. 4,764,278, discloses a method for reducing the concentration of haloorganic compounds in water by first extracting the haloorganic compounds from the water using a water immiscible alkane hydrocarbon solvent. The solvent is then separated from the water and regenerated by exposing the solvent to ultraviolet light to degrade the haloorganic compounds.
Ultrasonic energy has also been used in the removal of halogenated organics from an aqueous liquid. For example, Sittenfield U.S. Pat. No. 4,477,357 describes a process for removal of contaminants such as halogenated organics from a liquid. Halogenated organic materials in oil or water are mixed with an equal amount of an alkaline agent, such as a hydroxide or a carbonate of an alkali metal or an alkaline earth metal, and then exposed to ultrasonic energy to decompose the halogenated organic contaminant. The presence of the alkaline agent is said to significantly accelerate the dehalogenation and decomposition of organic ring structures. U.S. Pat. No. 5,130,031 to Johnston also describes the treatment of aqueous liquids using light energy, ultrasonic energy and a photocatalyst. Sierka et al., in xe2x80x9cCatalytic Effects Of Ultraviolet Light And/Or Ultrasound On The Ozone Oxidation Of Humic Acid and Trihalomethane Precursorsxe2x80x9d, describe the catalytic effects of the use of both UV irradiation and ultrasound, either singly or in combination, on the ozone oxidation of organic materials, such as humic acid, in aqueous solutions. It is believed that the most effective reactor conditions for both the destruction of nonvolatile total organic carbon and trihalomethane formation potential utilized both ultrasound and UV irradiation in combination with ozone.
Another known technique of removing contaminants from fluids comprises the use of illuminated photocatalysts such as titanium dioxide. The ability of ultraviolet illuminated titanium dioxide to destroy organic contaminants in water (Carey et al., Dull. Environ. Contam. Toxicol. 16, 697, (1976)) has been well known for many years. However, heretofore, none of the prior processes has emerged as a commercially viable process. There are several reasons why these prior processes have not been commercially successful.
First, current evidence supports the notion that destruction of organic contaminants occurs on the surface of the photocatalyst, and therefore an increase in surface area is required for high rates of reaction. To achieve this, slurries of colloidal titanium dioxide have typically been used in many processes; however, the recovery of the colloidal photocatalyst in the discharged effluent has not been cost efficient for high volume applications.
Second, immobilization of titanium dioxide on a support within the photoreactor has been suggested and has resolved the retention problem described in the previous paragraph. However, this solution has come at the expense of increasing mass transfer problems associated with movement of the contaminants in water to the immobilizing support which was more distantly spaced (for light penetration purposes) than the dispersed colloidal particles. Immobilization also creates a lack of uniformity in irradiation of photocatalytic particles, which are immobilized at different distances and with different orientations to the light source. Larger photoreactors would therefore be needed to cope with the inefficiencies introduced by immobilization. With colloidal slurries (i.e. previous paragraph), mixing provided all particles with equal probability of being in low and high light intensity regions of the photoreactor.
Third, when treating dilute solutions, the resulting mass transfer problems reduce significantly the rate of chemical destruction in both the slurried and immobilized titanium dioxide processes described above.
Unfortunately, these problems serve to restrict the fluid volumes treatable by a given amount of photocatalyst in any given time, and necessitate the use of large reactors to handle large fluid volumes. Since many applications, such as municipal drinking water purification, require treatment of large volumes with low concentrations of contaminants, prior art processes involving the use of photocatalysts in this manner have been severely limited for such applications.
In light of the foregoing, it is desirable to have a process capable of purifying aqueous solutions while minimizing or eliminating the above-mentioned deficiencies of the prior art. Ideally, such a process would be useful to remove chemical contaminants from aqueous solutions in a relatively simple and efficient manner, and would decompose or transform the removed contaminants to dischargeable and innocuous or otherwise desirable products which could, at the discretion of the user, be diluted with purified fluid or captured for further processing such as microbial treatment. Further, it would be advantageous if such a process could be easily adapted for purifying liquid and/or gas phase fluids.
In recent years, advanced oxidation processes have emerged as potentially powerful methods of transforming organic pollutants in water or air into harmless substances. These methods are called advanced oxidation processes because they promote free radical reactions, which lead to complete oxidation of the organic compounds to yield CO2, H2O and corresponding salts. In photocatalytic degradation the oxidizing species are generated from dissolved oxygen or from water, in situ, on the photocatalytic particles (i.e. TiO2), which absorb light.
While these methods have been shown to be successful in removing organic contaminants from aqueous liquids and decomposing such organic materials, the reaction times are slow leading to reduced economic attractiveness of such processes, especially for continuous or on line treatment systems.
Accordingly, it is an object of the present invention to provide an efficient and cost effective method for degradation of organic compounds in aqueous systems.
The present invention relates to method for treating a liquid contaminated with organic compounds which method will rapidly decompose the organic contaminants. The method provided eliminates the need to provide ultraviolet light energy. The present method comprises exposing a contaminated liquid to visible light while contacting the contaminated liquid with a semiconductor photocatalyst, wherein the semiconductor photocatalyst comprises a transition metal atom exchanged into the framework of a zeolite and/or mesoporous molecular sieve material, which are subsequently loaded with a photoactive material, such as titanium dioxide.
The present invention provides a novel process for efficiently removing organic compounds from contaminated aqueous liquids by contacting the contaminated liquid with a photocatalyst, while simultaneously exposing the contaminated liquid to visible light energy to decompose the organic compounds.
To be commercially feasible, photocatalytic degradation must be relatively inexpensive, safe, and use a nontoxic catalyst. The ideal method would produce no toxic by-products, utilize concentrated solar energy to reduce light energy costs, exhibit high yields, and be applicable to a wide variety of organics. It has been discovered that when photocatalytic degradation using a zeolite or other microporous molecular sieve, which has had a transition metal exchanged into its framework and then is loaded with titanium dioxide, in accordance with the present invention, the result is substantially higher degradation rates and the elimination of the need for UV light. The disclosed process has the potential to offer both improved rates and efficiencies (hence throughputs) under optimized conditions; the ability to use impure or cheaper forms of the photocatalyst; significantly increased degradation rates of aqueous organics without poisoning of the catalyst; improvements in conventional suspended catalyst separation methods such as ultrafiltration; and for applications involving treatment of waste water containing suspended solids, the use of sonication may also assist in the release of hydrophobic organics adsorbed on soil particles, for subsequent reaction at the photocatalyst surface.
The use of molecular sieves such as zeolites and mesoporous materials as support structures for transition metals is beneficial for many reasons. First, the well-defined porous structures (large surface area) of zeolites offer a special environment for the incorporation of transition metals, with unusual morphologies and thus altered photoactivity. Second, they allow pre-concentration of non-polar organic molecules and selective adsorption onto a zeolite. Third, zeolites enhance catalytic activity through properties ranging from surface acidity to reactive intermediate stabilization. Fourth, zeolites are believed to not scatter photons as strongly as TiO2 does. Fifth, transition metal ions exchanged into zeolites and mesoporous materials, create a narrow energy band inside the materials band gap.
Additionally, the materials with mesoporous character offer one other advantage when used in accordance with the present invention. The uniform one-dimensional mesopores such as those of MCM41 allow faster diffusion of oxygen, reactive species and organic substrates within the catalyst surface than the microporous zeolites.
Photocatalyst
By use of the term xe2x80x9cphotocatalystxe2x80x9d is meant any compound in which irradiation of such compound with electromagnetic radiation of visible wavelength will result in the generation of conduction band electrons (ecb) and valence band holes (h+vb) that can then undergo oxidation reactions at the catalyst surface with species such as water or inorganic and organic compounds. The initiating step in this photocatalytic process requires illumination with light of energy higher than the band gap of the semiconductor photocatalyst (e.g.,  less than 380 nm. for anatase TiO2, the most effective and widely studied photocatalyst). Electromagnetic radiation within a wavelength range of from about 250 nanometers (nm) to about 450 nm will usually have such an energy level.
The preferred photocatalyst is a zeolite or other mesoporous molecular sieve material that has had a transition metal exchanged into it and then is subsequently loaded with TiO2. Transition metals with unfilled d-levels are preferred. Using the rules of semiconductor doping, these are the transition metals capable of having a stable oxidation state one unit lower or one unit higher, than the host semiconductor. Thus, for TiO2 (oxidation state of titanium +4) the dopants capable of having stable +5 or +3 oxidation states are prefered but not required. Doping the catalyst with a transition metal creates a narrow energy band within the original band gap allowing for the generation of holes in the valence band and electrons in the conduction band, which are required for photocatalytic oxidation. Suitable transition metals include but are not limited to chromium, iron, nickel, manganese, copper, tungsten, cobalt, molybdenum, ruthenium, vanadium, zinc, silver, platinum, titanium and mixtures thereof.
The oxidation state of the metal is selected as desired by the formulator, for example manganese in the 0, +2, +3, +4, +5, +7 state, iron in the 0, +2, +3, +4, +5 state, vanadium in the 0, +2, +3, +4,+5 state, etc. The oxidative state of the large pore size mesoporous material catalyst may change during use consistent with its nature as an oxidative material.
These may be provided in a wide distribution of average particle sizes ranging from an average particle size of as small as, for example, from about 0.05 microns to as large as, for example, about 1,000 microns in diameter. Since large surface areas are desired for the photocatalyst to provide a large amount of active sites, small particles will be desired. It will be appreciated, however, that larger size particles could be used, i.e., particles larger than 1,000 micron in size. The particulate photocatalyst, such as chromium exchanged zeolite, may be added in dry form to the contaminated liquid and mixed together to form a suspension prior to exposure of the contaminated liquid to light energy. Alternatively, the dry particulate catalyst may be premixed as a slurry or suspension with an aqueous liquid miscible with the contaminated liquid, and this premix may then be added to the contaminated liquid prior to exposure of the contaminated liquid to light energy.
Typical zeolites and mesoporous materials include the commercially available ZSM-4 (Omega), ZSM-5, ZSM-11, ZSM-12, ZSM-20, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, MCM-22, PSH-3, MCM-48, MCM-49, Beta, X, Y, and L, as well as ferrierite, mordenite, dachiardite, clinoptilolite, offretite, erionite, gmelinite, chabazite, etc. Other molecular sieves contemplated include, for example, MCM-9, VPI-5, MCM-20, SAPO-11, SAPO-17, SAPO-34, SAPO-37, MCM-36, MCM-41, MCM-48, MCM-49 and MCM-53.
Also included within the definition of the useful molecular sieves are crystalline porous silicoaluminophosphates such as those disclosed in U.S. Pat. No. 4,440,871, the catalytic behavior of which is similar to that of the aluminosilicate zeolites. Zeolite Beta is described in U.S. Pat. No. Re. 28,341 (of original U.S. Pat. No. 3,308,069), to which reference is made for details of this catalyst.
Zeolite X is described in U.S. Pat. No. 2,882,244, to which reference is made for the details of this catalyst. Zeolite L is described in U.S. Pat. No. 3,216,789, to which reference is made for the details of this catalyst. Zeolite Y is described in U.S. Pat. No. 3,130,007, to which reference is made for details of this catalyst. Low sodium ultrastable zeolite Y (USY) is described in U.S. Pat. Nos. 3,293,192; 3,354,077; 3,375,065; 3,402,996; 3,449,070; and 3,595,611, to which reference is made for details of this catalyst. Dealuminized zeolite Y can be prepared by the method disclosed in U.S. Pat. No. 3,442,795, to which reference is made for details of this catalyst. Zeolite ZSM-3 is described in U.S. Pat. No. 3,415,736, to which reference is made for details of this catalyst. Zeolite ZSM-5 is described in U.S. Pat. No. Re. 29,948 (of original U.S. Pat. No. 3,702,886), to which reference is made for details of this catalyst. Zeolite ZSM-11 is described in U.S. Pat. No. 3,709,979, to which reference is made for the details of this catalyst. Zeolite ZSM-12 is described in U.S. Pat. No. 3,832,449, to which reference is made for the details of this catalyst. Zeolite ZSM-20 is described in U.S. Pat. No. 3,972,983, to which reference is made for the details of this catalyst. Zeolite ZSM-22 is described in U.S. Pat. No. 4,556,477, to which reference is made for the details of this catalyst. Zeolite ZSM-23 is described in U.S. Pat. No. 4,076,842, to which reference is made for the details of this catalyst. Zeolite ZSM-35 is described in U.S. Pat. No. 4,016,245, to which reference is made for the details of this catalyst. Zeolite ZSM-50 is described in U.S. Pat. No. 4,640,829, to which reference is made for details of this catalyst. U.S. Pat. No. 4,962,239 to which reference is made above is incorporated herein by reference in its entirety. This patent teaches a process for preparing ethers over catalyst comprising a particular class of zeolites, e.g., MCM-22 and PSH-3. MCM-36 is described in U.S. Ser. No. 07/811,360, filed Dec. 20, 1991, now U.S. Pat. No. 5,25,277, and is incorporated herein by reference in its entirety. MCM-41 is described in U.S. Pat. No. 5,098,684, to which reference is made for the details of this catalyst. MCM-49 is described in U.S. Pat. No. 5,236,575, and is incorporated herein by reference in its entirety.
Zeolite Catalysts
The zeolite particles useful herein are particles of a crystalline aluminosilicate corresponding to the formula: ((xM2,nO)(Al2O3)(ySiO2)).zH2O in which M is a cation, generally an ammonium or metal cation, commonly a mono- or divalent metal cation (e.g. a sodium, potassium, or other alkali metal cation, or another cation such as calcium or magnesium); n is the valence of the cation; x is the coefficient of the metal oxide; y is the coefficient of the silica; and z in the number of molecules of water of hydration. They are preferably zeolites having a particle size of 0.1-20 xcexcm (e.g., 2-5 xcexcm) and a SiO2/Al2O3 molecular ratio of less than or equal to 14, more preferably a zeolite A, zeolite C, zeolite X, or zeolite Y, most preferably a zeolite Y.
This invention relates to zeolite compositions topologically related to prior known zeolites but which are characterized as containing framework atoms of a transition metal, and preferably having a very low content of defect sites in the structure. Accordingly, one embodiment of the invention is a molecular sieve composition having a three-dimensional microporous framework structure of Al2O3, SiO2, TiO2 tetrahedral oxide units and having a unit empirical formula on an anhydrous basis of (TiwAlxSiy)O2 wherein w, x and y represent one of the mole fractions of Ti, Al and Si, respectively, present as framework tetrahedral oxide units. These molecular sieves can be prepared by contacting a starting zeolite with a solution or slurry of a fluoro salt of a transition metal under effective process conditions to extract aluminum from the zeolite framework and substitute for it the transition metal.
Mesoporous Material Catalysts
As used herein, the term xe2x80x9clarge pore size mesoporous material catalystsxe2x80x9d means any porous material having a mean pore size of greater than about 15 Angstroms and having oxidative catalytic properties resulting at least in part from the presence of metal bound to (under typical use conditions of the present invention compositions) the large pore size crystalline material. Preferred are oxidative catalysts.
The transition metal may therefore be present in the catalyst by physical interactions with the porous material, by ionic or covalent bonding, or by clusters of metals likewise bound or attached to the porous material.
The transition metal may be incorporated into the catalyst by adsorbing it as an aqueous cation, with or without simple ligands such as acetate. The transition metal may also be incorporated by adsorbing it as a volatile, low-valent metal carbonyl, with or without post-treatment to decarbonylate the adsorbed metal carbonyl in-situ.
Methods for attaching metals to porous materials, and attaching functional groups to porous materials to which metals may thereto be attached, are known in the art, being described for example in U.S. Pat. No. 5,145,816, issued Sep. 8, 1992 to Beck et al., and in xe2x80x9cA New Family of Mesoporous Molecular Sieves Prepared with Liquid Crystal Templatesxe2x80x9d, by Beck et al, J. Am. Chem. Soc., Vol. 114, No. 27, pp. 10834-10843 (1992), incorporated by reference herein in their entirety.
Preferred large pore size mesoporous material catalysts useful herein have mean pore size of about 20 Angstroms or greater, more preferably of about 100-1000 Angstroms, and most preferably about 500-600 Angstroms. Also, preferred mesoporous material catalysts herein have surface area of at least about 300 m2/g, more preferably at least about 400 m2/g and most preferred being at least about 500 m2/g.
Preferred large pore size mesoporous material catalysts are silicate or aluminosilicate catalyst materials. These include liquid crystal template synthesized silicate and aluminosilicate materials, such as those described in xe2x80x9cA New Family of Mesoporous Molecular Sieves Prepared with Liquid Crystal Templatesxe2x80x9d, by Beck et al, J. Am. Chem. Soc., Vol. 114, No. 27, pp. 10834-10843 (1992). These materials are additionally characterized by high crystallinity and low water solubility. Most preferred are such materials, which are crystalline on the basis of X-ray powder pattern.
Methods for evaluating the physical characteristics of the catalysts useful herein are well known in the art, being described for example in Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Vol. 5, pp. 383-418 (1993), the disclosures therein being incorporated herein by reference in their entirety.
Highly preferred are those catalysts described as xe2x80x9cmesoporous molecular sievexe2x80x9d materials as taught, for example, in U.S. Pat. No. 5,102,643, issued Apr. 7, 1992 to Kresge et al., U.S. Pat. No. 5,250,282, issued Oct. 5, 1993 to Kresge et al., U.S. Pat. No. 5,264,203, issued Nov. 30, 1993 to Beck et al., U.S. Pat. No. 5,145,816, issued Sep. 8, 1992 to Beck et al., and U.S. Pat. No. 5,098,684, issued Mar. 24, 1992 to Kresge et al., the disclosures of all these patents being incorporated herein by reference in their entirety.
One particularly preferred mesoporous material is MCM-41. MCM-41 refers to a mesoporous material with a hexagonal silicate phase MCM-41 can be successfully synthesized using the method described by A. Sayari et al. (Chemistry Materials, 9, 1997).
Exchange of Transition Metal Atoms for Al Atoms
Transition metal atoms, such as chromium or iron can be effectively xe2x80x9cexchangedxe2x80x9d with the aluminum atoms of the zeolite or mesoporous material framework. The zeolite powders already contain aluminum, and the mesoporous material is synthesized (described below) to contain aluminum. The cation exchange is performed by use of salts of weak organic acids and corresponding transition metals in a slurry formed with each zeolite or mesoporous material and distilled water. Chromium acetate, ammonium-titanium oxalate and vanadium oxalate can serve as examples of such salts. The slurry is vigorously agitated at ambient temperature for approximately 10 hours. The catalyst is then filtered using conventional filter paper and washed thoroughly with distilled water. Other titanium salts can be used for this as long as they do not result in the formation of a very acidic environment or the destruction of the zeolite or mesoporous molecular material itself. It will be understood by one of skill in the art, that the size of the precursor used must be smaller than the pore openings of the zeolite or mesoporous molecular material.
There are a number of analytical techniques known in the art, which can be used to confirm that the transition metal has been successfully exchanged into the zeolite or mesoporous material. These techniques include: extended X-ray absorption of fine structure (EXAFS), Raman infrared spectroscopy and high resolution transmission electron microscopy.
It should be understood by one of skill in the art that to achieve a photocatalyst containing a transition metal it is not required that one start with an aluminum containing framework. That is to say that the photocatalyst can be synthesized to incorporate the transition metals in the framework from the very beginning.
Loading with TiO2
Titania is loaded into the pores of zeolites or mesoporous molecular materials such as USY and MCM-41 after a transition metal or titanium has been exchanged into the framework or incorporated into the framework during synthesis. This is also commonly referred to as doping of the materials with titania. A slurry of each zeolite or other mesoporous molecular material is formed and 0.5-50% of precursor is added to result in the desired titania loading. Typically the amount of titania loaded is less than 25% by weight of the catalyst to avoid blocking of the pores. Higher concentrations may be used but are not deemed to be necessary and would add expense to the process in terms of material costs. The precursor used to load the zeolites is ammonium-titanium oxalate and the precursor for the mesoporous molecular material is titanium-isopropoxide. Other titanium salts can be used for this as long as they do not result in the formation of a very acidic environment or the destruction of the zeolite or mesoporous molecular material itself. It will be understood by one of skill in the art, that the size of the precursor used must be smaller than the pore openings of the zeolite or mesoporous molecular material.
The concentration of the particulate photocatalyst in the contaminated liquid should range from about 100 milligrams per liter of contaminated liquid to about 2 grams per liter of contaminated liquid. Higher concentrations may be used but are not deemed to be necessary and only would add expense to the process, both from the standpoint of additional material costs as well as additional processing costs, e.g., if the catalyst must be separated from the purified liquid after the organic compound has been decomposed. Typically, the concentration of the photocatalyst in the contaminated liquid will be about 1 gram per liter. Lower concentrations may be used, but this may result in a lowering of the decomposition rate. In this regard, it will be appreciated that the actual amount of catalyst used will depend upon the surface area of the catalyst, which will, in turn, depend upon the porosity and/or particle size of the particulate catalyst. A typical surface area range will be from about 1 to about 1000 meter2/gram of photocatalyst such as for example titanium exchanged USY zeolites.
Zeolite Membranes
Generally speaking, in accordance with the invention, methods are provided for forming membranes of semiconductive materials loaded molecular sieve materials, such as zeolites, having a transition metal atom exchanged therein. The semiconductors, such as metal oxides, are photoactive and are useful in photocatalytic reactions. Methods for forming the membranes can involve sol gel techniques and surface reaction techniques. An example of such a membrane is titanium oxide-loaded zeolite molecular sieve, which has a transition metal atom exchanged therein. Photoactive semiconductors suitable for use herein include titanium dioxide, zinc oxide, cadmium sulfide, iron oxide, gallium phosphide, tin oxide, silicon carbide, tungsten oxide, and mixtures thereof. Membranes in accordance with the invention can be used to perform useful chemical reactions such as the mineralization of organic chemicals in the presence of light. For example, many toxic organic chemicals can be converted to useful or benign products by contacting those chemicals with active metal oxide-molecular sieve membranes in accordance with the invention and illuminating the membranes with light of a suitable wavelength. An object of the invention is to increase the photoefficiency of conventional membranes. It has been discovered that the quantum yield of TiO2 photocatalyzed reactions can be markedly increased by combining the TiO2 material with a molecular sieve in the form of a membrane while exposing to light energy during the reaction. Methods for forming membranes of semiconductive material incorporating molecular sieve material can be found in U.S. Pat. No. 5,712,461.
Aerogels Transition metals such as chromium can be easily incorporated into low-density nanoscale mesoporous aerogels. Aerogels are a class of materials composed of about 10 nm particles connected in a highly porous (80-90% by volume), three-dimensional network. Because aerogels provide both high surface area (up to 1000 m2/g) and highly open space, they are well suited to catalytic applications. Especially composite aerogels lend themselves towards the formation of titania aerogels. Morris et. al., in Science, vol. 284, pp. 622-624, 1999, describes the efficient illumination of aerogel-incorporated titanium, because the silica aerogel is transparent throughout most of the ultraviolet-visible region.
Light Source
As stated above, the radiation source should be a light source, which provides energy higher than the band gap of the semiconductor catalyst. To accomplish this, the electromagnetic radiation or light source will be within the visible wavelength range of from about 380 nm to about 750 nm, which is considerably broader than the range for conventionally used anatase titania (UV radiation from about 250 to about 380 nm). The intensity of the light source will be inversely proportional to the amount of time which it will takes to affect the desired decomposition of the organic compounds, i.e., the weaker the light source, the longer the decomposition time will be. This, in turn, will affect the overall efficiency of the process and will be of particular importance when the process is being run on a continuous basis rather than as a batch operation.
A number of zeolite- and mesoporous materials hosted photocatalysts have been synthesized and have shown a remarkable shift of the absorption spectrum towards the visible range of the light spectrum. Transition metal exchanged zeolites and mesoporous materials, especially those containing Iron or Chromium, can utilize visible light energy, as it has been surprisingly found that their absorbency at 452 nm is greater than 50%. Not wishing to be bound by theory it is believed that the transition metals create additional energy levels in the band gaps of the semiconductors due to unfilled d-orbitals present in the transition metals. This eliminates the necessity for a UV light source and renders solar or visible light capable of activating the photocatalyst, resulting in a substantial cost saving.
For a light source which is coupled directly to an optical cell containing the contaminated liquid, the intensity of the light source, at the selected wavelength should be at least about 1,000 microwatts per inch2 of exposure area per liter of liquid to achieve complete decomposition within a reasonable exposure period. Such light sources are commercially available, e.g., a Quartz-Halogen Tungsten lamp source, fluorescent lamp or sunlight may be used as the source of short wave length light radiation. The distance that the light source is located from the liquid to be irradiated is important since much of the light energy may be absorbed within a few cm. of the liquid surface. Therefore, depending upon the size and geometry of the reaction vessel, as well as the intensity of the light source, it may be appropriate to use a plurality of such light sources dispersed around the perimeter of the vessel, as well as above and below the respective top and bottom surfaces of the vessel.
In general, it may be stated that the relationship of the intensity of the light source (or sources) to the dimensions of the reaction vessel should be such that the light entering the reaction vessel will still have sufficient intensity or energy to initiate photocatalytic decomposition of the organic material in the liquid when it reaches the farthest extremity of the volume of the vessel. For a single light source, for example, this would mean the opposite wall of the vessel. However, if a plurality of such light sources were to be spaced around the perimeter of the reaction vessel, this distance would mean the distance to the center of the vessel.
It should be noted in this regard that the decomposition rate will be dependent upon not only the intensity of the light source and the dimensions of the reaction vessel, but also on the type and concentration of catalyst, and the type and concentration of the organic material being decomposed.
The light source needs not be constant. It is possible to provide a modulated or pulsed light to achieve the same efficiency of degradation. For example, the light is generated in a modulated or pulsed manner, which includes subsequent time-on and time-off intervals. The modulated or pulsed light may have a duty cycle, wherein the ratio of the light time to the total time of the cycle ranges from 5% to 50% and the light time is less than one second. In one embodiment, the light time is less than 500 milliseconds, and in another embodiment, the light time is less than 100 milliseconds.
Types of Organic Compounds Degraded
All types of organic compounds can be cleaned from contaminated liquids by use of the present invention. The type and size of the compound to be removed from the liquid will determine the pore size of the catalyst that should be used. The organic compounds present in the contaminated liquid to be purified may comprise halogenated compounds such as, chlorinated phenols (e.g., 2,4-dichlorophenol, 4-chlorophenol, pentachlorophenol), chlorinated biphenyls (e.g., 3-chlorobiphenyl and 4,4xe2x80x2-dichlorophenyl), brominated biphenyls, and halogenated benzene derivatives (e.g., chlorobenzene, 4-chlorotoluene, chlorinated dioxin, and halogenated benzofurans). Examples of halogenated aliphatic organics include halogenated hydrocarbons such as fluoromethanes, ethanes, propanes, etc.; chloromethanes, ethanes, propanes, etc.; bromomethanes, ethanes, propanes, etc.; and mixtures of same; halogenated alkenes, such as trichloroethylene; halogenated alcohols, such as 1-chloro-2-propanol; halogenated ketones; halogenated aldehydes, such as aldrin aldehyde; halogenated carboxylic acids, such as trichloroacetic acid; and halogenated ethers, such as bis(2-chloroisopropyl)ether. Other organic compounds which can effectively be removed from contaminated liquids include, but are not limited to, aromatics and polyaromatics, paraffins, olefins, ketones, aldehydes, organic acids and alcohols. A representative, but non-exhaustive listing, of different kinds and types of organic material able to be degraded is provided by Table I below.
A cursory reading of Table I will reveal many classes of substances whose members have been classified as toxic, environmentally hazardous compositions by federal and state agencies such as the EPA, OSHA, and NIOSH. In addition, many of these substances are known or believed to be carcinogenic or carcinogen-promoters whose use is carefully controlled by various health and safety agencies. All of these comprise the membership of the general class of organic material able to be completely degraded into environmentally safe reaction products comprising at least carbon dioxide.
The concentration of such organic compounds in the aqueous liquid may range from as little as 2 ppm, to as much as 2,000 ppm. After purification by the process of the invention, the concentration of such organic impurities in the previously contaminated liquid may be reduced to less than 1.0 ppm. Exposure of the contaminated aqueous liquid containing such organic compounds to visible light radiation energy, in the presence of the particulate catalyst, results in decomposition of the organic compounds into purified liquid, environmentally compatible reaction products comprising at least carbon dioxide which may then be subsequently removed from the liquid. A separate source of oxygen is usually not necessary for the formation of the CO2 decomposition product, since there will normally be sufficient dissolved oxygen in the aqueous liquid. However, a separate source of oxygen (e.g. ozone, H2O2) may be optionally provided if desired, which could be introduced into the contaminated liquid through a sparger ring or the like. Although not required, ultrasonic energy can be added to the process to further enhance its efficiency.
Process
A contaminated liquid or gaseous source such as water containing halogenated organic contaminants, in a concentration which may range from about 2 ppm to about 2,000 ppm, is mixed with a source of particulate catalyst which may be in dry form or, preferably, in a previously formed suspension or slurry. The optical cell may comprise any reaction vessel having sidewalls (or one or more openings in the sidewalls) transparent to visible light, to permit the liquid in optical cell to be irradiated by light energy from a light source, which is preferably coupled directly to the sidewall of the cell to permit the most efficient coupling of the light energy to the cell from the source. While the light source has been described as a single source, it will be readily appreciated that the light energy may be passed through the transparent sidewalls or windows through a plurality of such light sources arranged around the periphery of the optical cell, as previously discussed, to uniformly illuminate the liquid therein with light of the proper wavelength during the decomposition of the organic compounds in the contaminated liquid in cell.
The optical cell may be further provided with temperature controlling means to maintain the liquid being treated within the cell within a temperature range of from about 15xc2x0 C. to about 60xc2x0 C. Pressure control means may also be provided to increase the hydrostatic pressure within the cell from sub-atmospheric pressure up to a pressure of about 500 psi. The organic compounds in the aqueous liquid decompose in the optical cell upon exposure to the light radiation in the presence of the particulate photocatalyst. The decomposition rate will be dependent upon the cell volume of contaminated liquid being treated, the type of contaminated liquid, the intensity of the light energy source and, when the process is being run on a continuous basis, the throughput or flow rate of the contaminated liquid through the cell.
The process of the present invention may be carried out at a relative humidity of from 5% to 100%.
It will be understood by one of skill in the art that the aforementioned process will be slightly modified when treating gaseous fluids. In a typical variation, a film of the catalyst will be deposited on a solid substrate, which will serve as the bottom or a sidewall of the photocatalytic reactor. The contaminated air or gaseous stream is passed over the layer of illuminated catalyst and the contaminants are degraded in the same way as in an aqueous system.
Optional process steps include the addition of ultrasonic energy or ozone to further enhance the efficiency of degradation.
Experimental Design and General Protocol
The experiments hereinafter employ the solid catalyst, either as an aqueous slurry which was fully coated onto a solid support material (such as the internal surface of the reaction cell wall); or as an aqueous slurry which was partly coated onto a solid support and partly dispersed in the fluid reaction medium; or as a suspension completely dispersed into the fluid reaction medium alone. There is no meaningful difference in the quality or quantity of reaction products obtained via the positioning of the solid catalyst.
All catalysts were characterized using Nicolet powder X-ray diffractometer equipped with a CuKa source to assess their crystallinity. MCM-41 powders were run from 2 to 7 degrees (2xcex8) to assess the crystallinity of the matrix and from 20 to 50 to assess the crystallinity of the TiO2 loading. USY-based samples were run from 8 degrees to 50 degrees corresponding to both loading and support. Furthermore, the powders were characterized by UV-Vis Shimadzu 2501PC with an integrating sphere attachment ISR1200 for their diffuse reflectance in the range of wavelengths of 200 to 800 nm. BET and pore size distribution studies are being conducted (using Micromeritics Gemini apparatus) to characterize the synthesized MCM-41 and USY-2.6 samples.
The photocatalytic testing (photodegradation of phenol with an initial concentration of 2 mM) was performed in a batch quartz reactor (Ace Glass) using 450W UV-Visible mercury lamp with a UV filter transmitting about 0% of intensity at wavelengths below 380 nm. The suspended catalyst in aqueous system was mixed, oxygenated, and irradiated during each reaction run. The concentration of formic acid in the reactor was controlled using a thermal conductivity detector. Typical loading of the solid catalyst varied from 1-10 grams per liter of fluid reaction mixture.
The following examples are presented to further illustrate, but not to limit, the practice of the process of the invention:

Photocatalytic degradation of organic compounds


A panty liner which includes active additives, such as lactobacilli. The liner includes a liquid-permeable top sheet which lies proximal to the wearer in use, a liquid-impermeable backing sheet which lies distal from the wearer in use, possibly an intermediate absorbent layer, and possibly fastener means. The panty liner is manufactured in a manner such that the active additives, preferably lactobacillus, are given a sufficiently effective and dry environment to ensure a healthy survival rate of the additives until the product is used.

The present invention relates to panty liners that contain active additives, such as lactobacillus, and comprise a liquid-permeable top sheet which lies proximal to the wearer in use, a liquid-impermeable backing sheet which lies distal from the wearer in use and possibly an intermediate absorption layer and possibly also fastener means.
In recent times, various types of active additives have begun to be used in absorbent products, such as diapers, panty liners and the like. Examples of such additives are deodorants such as zeolites and silica described in WO 97/46188, WO 97/46190, WO 97/46192, WO 97/46193, WO 97/46195 and WO 97/46196, for example. These additives are intended essentially to act in the product per se. Another example resides in the addition to diapers of softening additives, for example lotions, that are intended to be transferred from the product to the wearer""s skin.
Active additives are intended to impart new or enhanced properties to the absorbent product in some respect. Lactic acid forming bacteria (lactobacillus) (mentioned in SE 9703669-3, SE 9502588-8, WO 92/13577, SE 9801951-6, SE 9804390-4, WO 00/01206 and WO 00/01207, among others), are applied to that part of the absorbent product which lies proximal to the wearer in use and are intended to be transferred to the wearer""s genitals as a supplement to the wearer""s own lactobacillus. This is particularly of value in situations where the own lactobacillus flora is weakened. For example, females of a fertile age naturally have lactobacillus in their genitals as a defence against undesired micro-organisms.
Since lactic acid forming bacteria (lactobacillus) are living organisms, and indeed must be alive in order to carry out their desired functions, it is important that the environment in which it such bacteria are present does not have a negative influence on their survival. This has been found problematic with regard to the development of products that include lactobacillus as an active component. It has been found that the survival of lactobacillus is negatively influenced primarily in a high humidity environment at room temperature. In order to ensure that the lactobacillus have a healthy storage environment, there has been developed a packaging unit which is sufficiently impervious to prevent the ingress of moisture during the storage period (WO 00/01207). The product is also subjected to a drying stage immediately prior to packaging the product, so as to ensure that the moisture content of the product will be sufficiently low when the package is sealed. This additional process step is, however, complicated and expensive. Consequently, there is a need for another production process or another lactobacillus-containing product that can provide for the lactobacillus a good and dry environment that is effective in ensuring healthy survival of the bacteria during storage.
The object of the present invention is to provide an absorbent article, primarily a panty liner, which enables the active additives to retain their activity prior to use of the product, without requiring further treatment, such as drying of the product to a greater or lesser extent.
This object is fulfilled with a panty liner that contains active additives, such as lactobacillus, and that comprises a liquid-permeable top sheet which lies proximal to the wearer in use, a liquid-impermeable backing sheet which lies distal from the wearer in use, optionally also an intermediate absorbent layer and optionally a fastener means, characterised in that the panty liner is produced chiefly from one or more low hygroscopic materials chosen from group of materials: non-woven, wadding, tow, and other synthetic fibre materials, wherein the moisture content of the panty liner is less than 2.5% after twenty-four hours at 22.5xc2x0 C. in an humidity of 46%, preferably less than 2.0%, and more preferably less than 1.0%.
It has been found that under normal conditions such a panty liner will not absorb moisture to an extent that will have a negative effect on the healthy survival of the lactobacillus during storage. The panty liner may also include a superabsorbent for absorbing fluid that must, of necessity, be taken-up, such as menstruation fluid, this amount corresponding to 2-4 g fluid in normal cases. Thus, the superabsorbent material, which is applied in the core of the product, will take-up the fluid that must be taken-up in order for the product to fulfil its function in use. Although the remaining synthetic tow or wadding material has no appreciable hygroscopic capacity, it has a highly effective dry content at room temperature, which provides the lactobacillus with a dry environment during storage.
Paper based materials of different kinds are normally used in typical products of this kind. For example, pulp fibres, among other things, are most often used in the core of the article, because besides being hydrophilic, such fibres absorb moisture and liquid effectively and are inexpensive. By avoiding the use of paper fibres, as in the case of the present invention, there is achieved a lower moisture content in the product and therefore a higher survival rate of the lactobacillus. A sufficiently effective absorption capacity is obtained in the product with the use of superabsorbents that have the capacity of absorbing anticipated volumes of liquid discharged in use, i.e. a typical volume of about 0-4 ml. In this case, the liquid take-up is concentrated at the core and the remainder of the panty liner is made of material that does not tend to absorb moisture.
The superabsorbent material used may have the form of small SAP grains, large SAP grains, or SAF (superabsorbent fibres). The absorbency of the article with respect to body fluids will therewith be sufficient without having the capacity to take-up an unnecessarily large amount of atmospheric moisture.
According to one embodiment, the product contains no superabsorbent, which is functional in those cases where no fluid is expected to be absorbed in use. This particularly applies to those cases in which it is only desired to transfer the lactobacillus to the wearer in use.
The product may conveniently be provided with a breathable backing sheet, so that less perspiration will be produced when wearing the product, and so that the product will not take-up an unnecessarily large amount of moisture.
By low hygroscopic material is meant material that is able to take-up atmospheric moisture in an amount sufficiently low to maintain a substantially dry environment under normal storage conditions, for example material such as tow, wadding and other synthetic fibre materials.
By tow is meant here a synthetic material consisting of long polypropylene fibres that have been bonded by transversal welds so as to hold the material together.
Wadding is a synthetic high loft material which, for instance, is needled by thin air, resin bonded, thermobonded, or bonded by carded or combed fibres. Wadding is available commercially from, e.g., Libertex.
The inventive panty liner is comprised of a liquid-permeable top sheet, a liquid-impermeable backing sheet, and optionally an intermediate absorbent body. The active additives, preferably lactobacilli are applied in the close proximity of the top sheet. In order to ensure that the lactobacilli will survive and retain their activity until the product is used, it is important in accordance with the inventive concept that the material from which the panty liner is made will attract as little moisture as possible. Trials have shown that a moisture content of 2.5 weight-% is an upper limit value beneath which survival of the lactobacilli is good. Consequently, an inventive panty liner is made of material which will absorb less moisture than said upper limit under tested conditions (see Example 1), such as wadding and-tow, for instance.
Superabsorbent (SAP) is preferably used in order to satisfy those absorption requirements that can arise in use. When a superabsorbent is used, it may also be beneficial to apply a dispersion layer beneath the top sheet, in order to ensure that the liquid delivered by the wearer is led to the superabsorbent material.
In one embodiment, the low hygroscopic material is tow.
In another embodiment, the low hygroscopic material is wadding.
In another embodiment, the top sheet and the wadding are joined together by punctiform bonds or by linear bonds that form a pattern. This is achieved by welding or by applying a high pressure at points, along short lines (dashes) or in some other pattern, wherewith the width of the points or lines in the pattern is about 1-7 mm. This results in a combination of larger and smaller capillaries that promote liquid absorption and transportation of liquid to lower layers.
In a further embodiment, the low hygroscopic material is thick non-woven, for example carded, spun-bonded, or a white or brown non-woven, xe2x80x9cEvolonxe2x80x9d having splittable fibres, with a weight per unit area of 80-140 g/m2, available from Freudenburg, or microfibres.
The superabsorbent material used in the inventive panty liner may have the form of SAP grains, e.g. Hysorb C 7100 from BASF, acid SAP, or SAF fibres. The superabsorbent material is applied in an amount in which it is able to absorb 0-6 g liquid, preferably 2-4 g liquid. This requires an addition of 0.1-0.5 g superabsorbent.
In one embodiment, the panty liner contains no superabsorbent.
When conditioning the inventive panty liner over a period of twenty-four hours and at a temperature of 22.5xc2x0 C. and a humidity of 46%, the panty liner will have a moisture content that is lower than 2.5%, preferably lower than 2.0%, and most preferably lower than 1.0%.
By active additive is meant a substance, an agent or a composition that is applied to the absorbent article during its manufacture and that is intended to change or improve the function of the article in some way or another. Examples of active additives are deodorisers such as zeolite and silica, softeners, such as lotions, lactobacillus for inhibiting the cultivation of other micro-organisms, and acids, such as lactic acid and citric acid, acid SAP, and partially neutralised SAP which is intended to lower the pH and thereby inhibit bacterial growth. The active additive may, for instance, be a micro-organism. According to one preferred embodiment of the invention, the active additive is an acid-producing micro-organism. According to a more preferred embodiment of the invention, the active additive is a lactobacillus and more preferably a lactobacillus of the strain Lactobacillus plantarum LB 931 (deposition No. (DSM): 11918).
When the active moisture-sensitive additive is lactobacillus, the additive can be applied in the form of a freeze-dried powder containing lactobacilli, or in the form of a suspension that contains lactobacilli. In this regard, it us suitable to keep the water content as low as possible or the concentration of lactobacilli as high as possible in the suspension, so as to avoid the addition of unnecessary water that must be later dried off. Lactobacilli will preferably be applied in an appropriate quantity of 104-1011, preferably 106-1010 CFU/product (CFU: Colony Forming Unit).
The liquid-permeable top sheet is comprised of a soft skin-friendly material. The top sheet may be comprised of a layer of different types of non-woven fibre material, or most beneficially of tow or wadding. Other materials that can be used are perforated plastic films, plastic nets, stitched, crocheted or woven textiles, and combinations and laminates of these types of materials. The plastic may be a thermoplastic, for instance polyethylene (PE). The non-woven material may consist of synthetic fibres, such as polyethylene (PE), polypropylene (PP), polyurethane (PU), a polyester, nylon or regenerated cellulose, or a mixture of different fibres. All materials that are used for liquid-permeable top sheets in the production of absorbent articles, such as sanitary napkins, panty liners or incontinence guards, can be used for the liquid-permeable-top sheet of the inventive article, and it will be understood that the aforesaid materials have only been given by way of example, provided that they have effective acquisition properties.
The liquid-impermeable backing sheet consists of a flexible material, preferably a thin film of polyethylene (PE), polypropylene (PP) or a polyester, although it may alternatively consist of a laminate of liquid-permeable material, such as non-woven, wadding or tow, and a liquid-impermeable material. All materials used in liquid-impervious backing sheets for absorbent articles may be used. The backing sheet may, beneficially, be air-permeable.
When using superabsorbents, it is normally necessary to include in the absorbent article a dispersion layer for leading the liquid to be absorbed from the top surface of the article to the superabsorbent polymers. These polymers are normally comprised of paper fibres (cellulose fluff), which is hydrophilic and has capillarity. According to the invention, the dispersion layer is conveniently comprised of synthetic fibre wadding, which is not hydrophilic and therefore does not absorb liquid to the same extent as cellulose fluff. Such a dispersion layer also includes capillaries for dispersing the liquid that is absorbed. Wadding includes relatively large capillaries or pores and when these capillaries or pores are, e.g., welded to a surface material, there are created smaller capillaries/pores that have a greater liquid retention capacity. The presence of a dispersion layer reduces the risk of discharged fluid running to and over the edge of the panty liner and therewith discolouring the panties or other garments of the wearer. It can be suitable to include a liquid acquisition layer (dispersion layer), even when the top sheet itself has good liquid acquisition properties.
With respect to packaging of the inventive panty liner, reference is made to packages and packaging methods disclosed in WO 00/01207.
The panty liner has a length of 60-260 mm. The absorption body has a widest width of 30-80 mm, preferably about 70 mm, and a smallest width at its rear end of 5-20 mm, preferably about 10 mm.
The panty liner is produced conventionally, for example in length-wise production in a one-path or four-path continuous production line.
A number of devices can be used to fasten the panty liner to the wearer""s panties, such as tabs, flaps (wings), adhesive strings or friction surfaces. The panty liner will preferably include flaps or wings that can be folded around the edge of the wearer""s panties and therewith fold the liner in place. The flaps, or wings, may be provided with adhesive strings that are covered with release paper in their packaged state, such release paper consisting of silicone-coated paper that functions to protect the adhesive strings against contaminating substances, such as dust, dirt and the like, and also prevents said strings from drying-out prior to use. Alternatively, it is conceivable to replace the adhesive strings with friction coatings or the like in the region of the absorbent body. Moreover, solely one flap may be provided with adhesive strings, although it is then necessary for the flaps to be dimensioned so that they will mutually overlap subsequent to being folded-in against the underside of the wearer""s panties, or after having been folded around the edges of the panties. Fastener devices other than adhesive may be used to fasten the panty liner to the wearer""s panties, e.g. hook devices of the touch-and-close fastener type capable of co-acting with the textile material from which the panties are made.
Although the invention is primarily concerned with a panty liner, it will be understood that the inventive concept also includes other absorbent articles in which active additives are used.
The invention will now be described by way of an example, although it will be understood that the example ahs no limiting effect on the scope of the invention.