The present invention is directed to a method for applying an aqueous polymer dispersion to a substrate involving forming a viscosity of from 10 to 5,000 mxc2x7Pas, and applying the dispersion to a substrate at a pressure of from 100 to 1500 psi. The method is useful with porous substrates, and especially in non-woven materials. The process provides a precise means of coating a polymer dispersion on the surface of a substrate, or with controlled penetration into the substrate.

This invention relates to a method for applying a polymer dispersion in a precise manner to a substrate, through the use of airless spray technology. The method provides application flexibility for applying the polymer dispersion on the surface of a substrate, or with controlled penetration into the substrate. The method is particularly useful in applying a polymer dispersion to the surface of a porous substrate, and especially useful for applying a binder or a surface treatment to a non-woven substrate.
Aqueous polymer dispersions can be applied to a substrate in many ways, including brushing, immersion (saturation), foaming, and spraying. Spray application is known in the industry as an efficient and high-speed means of applying liquid coatings to substrates.
Spray application of polymeric dispersions is used in the production of non-woven materials. The polymeric dispersions are used as binders to consolidate the base-sheet, used for control linting in Multi Bonded Airlaid (MBAL) materials, or used as surface treatments. Current spray processes used in the production of non-woven materials require that the polymer dispersion be diluted with water, making accurate control of binder distribution within a fiber matrix difficult. Typical spray bonding processes involve dilution of a polymer dispersion to between 10 and 35 percent non-volatile content in order to achieve satisfactory atomization. Application of polymer resin to the non-woven occurs using a spray boom, containing nozzles positioned across the web profile, which are fed from a sealed pressure vessel.
Current polymer spray systems work well for through fiber coating of the non-woven material, resulting in a coating of both the surface and core of the non-woven substrate. Current methods do not allow for surface application only, primarily due to the low viscosity of the diluted dispersion. For precision application, a higher solids dispersion must be used in order to minimize penetration of the substrate, and must be used in conjunction with a system that offers superior atomization of the wet dispersion. Current spray bonding is also prone to over-spray and line contamination.
U.S Pat. Nos. 4,515,836 and 5,573,429 describe the use of airless spray technology for the application of a coating to plastic bottles. In the described airless spray process, higher solids polymeric dispersion (typically from 40 to 60 percent) are applied to plastic bottles.
There is a need for a high-speed process for applying a polymer dispersion in a controlled manner onto, or into, a porous substrate, particularly in the non-wovens industry.
Surprisingly it has been found that polymer dispersions, having viscosities of between 10 and 5,000 mxc2x7Pas can be applied in a precise manner to porous substrates using an airless spray process. One advantage of the process is the ability to use commercial polymer dispersions without the need for dilution. Another advantage is that at the higher solids levels, the polymer dispersion can be applied to the surface only. This precise application of polymer leads to less polymer usage, and the higher solids dispersions require less time and energy to dry, thereby reducing manufacturing costs.
The present invention is directed to a method for applying an aqueous polymer dispersion to a substrate comprising:
a) forming a polymer dispersion having a viscosity of from 10 to 5,000 mxc2x7Pas;
b) applying said dispersion to a substrate by use of airless spray at a pressure of from 100 to 1500 psi.
The present invention relates to a method for applying a polymer dispersion in a precise manner to a substrate, through the use of an airless spray.
An aqueous polymer dispersion, as used herein, refers to polymer particles dispersed in water. The dispersion may be formed by any means known in the art, such as emulsion polymerization, inverse emulsion polymerization, suspension polymerization, and the dispersion of polymer particles into water which are either self-dispersing, or are stabilized using colloid stabilizers, surfactants, or both. Natural polymers may be dispersed with or without the use of stabilizers and/or surfactants.
By airless spray, as used herein, is meant the application of an aqueous polymer dispersion to a substrate using hydraulic pressure instead of air to atomize and spray liquids. This technology involves forcing a polymer dispersion through a small, precise orifice at a pressure of from 100 to 1500 psi. This process results in the dispersion forming a fan pattern containing virtually no air turbulence, and thereby minimal overspray. The absence of air also reduces the droplet velocity, thereby minimizing the disturbance of the web.
Cross-cut nozzles, dome nozzles, and other types of nozzles can be used in the airless spray process. A cross-cut nozzle capable of providing precise fan patterns is preferred over standard airless nozzles. As a cross-cut nozzle wears, the fan pattern widens creating an acceptable problem of over-lapping coverage. As a standard nozzle wears the fan pattern narrows, creating unacceptable gaps between adjacent fan patterns.
The airless spray system ideally includes a high quality filtration system to minimize the risk of nozzle clogging. A high pressure pump is used to pressurize the dispersion to between 100 and 1500 psi. It is noted that a standard air driven piston pump can cause momentary interruptions in sprays as the pump shifts strokes, which could lead to uneven distribution of the polymer dispersion. This problem can be eliminated with appropriately designed fluid circuits using constant pressure pumps or surge chambers, and/or fluid regulators.
Pre-atomization may optionally be used in the present invention. Pre-atomization essentially involves the generation of turbulence within the polymer dispersion prior to entering the nozzle, which can assist in optimizing atomization.
The aqueous polymer dispersion may include any polymer or a mixture of polymers known in the art, and can be made by means known in the art. Polymers useful in the present invention include both natural and synthetic polymers; and homopolymers, copolymers, block polymers, multi-stage polymers, and star polymers. Examples of useful polymer chemistries include, but are not limited to, ethylene vinyl acetate polymers, acrylic homopolymers and copolymers, vinyl acetate homopolymers, starches, cellulosics, all with and without cross-linking capability. Stabilization of such dispersions can be achieved using a wide variety of chemical species, including low molecular weight emulsifying agents, such as anionic, nonionic, cationic, and amphoteric surfactants; high molecular weight protective colloids, such as polyvinyl alcohol, cellulosics, dextrines and starches; or a combination thereof. The polymer may be functionalized to improve performance characteristics after it is applied to the substrate. This includes cross-linking and self-cross-linking functionality, and the range of fully redispersible polymer dispersions to water repellent hydrophobic polymer dispersions. Preferably, the dispersion is not excessively thixotropic in behavior when used with a cross cut nozzle. Polymer dispersions having Newtonian flow characteristics can be used with dome nozzles without preatomization.
The key parameters of the dispersion are the viscosity and solids level. The solids level is preferably maximized to reduce the amount of water that must be removed following application. The viscosity dictates the degree of atomization. Useful viscosities are from 10 to 5,000 mxc2x7Pas, and preferably 100 to 2,000 mxc2x7Pas at the temperature of application. Optimum atomization is obtained using dispersions having a viscosity of from 100 to 2000 mxc2x7Pas. Dispersions with viscosities in excess of 2000 mxc2x7Pas can be used with the airless spray system, but require additional air pressure and possible warming. The viscosity of the dispersion must be within a range that can be handled by the airless spray equipment. Warming the dispersion to temperatures up to 90xc2x0 C., preferably to a temperature of 20xc2x0 C. to 70xc2x0 C., and most preferably to a temperature between 40xc2x0 C. and 60xc2x0 C. provides for the use of higher solids content without exceeding viscosity limitations. The use of heated polymer dispersions offers exceptional control of polymer positioning down to very low add-on levels with a minimum of overspray. Add-on levels of 3 grams per square meter and lower can be achieved. The viscosity level is irrespective of the non-volatile content.
Polymer dispersions having any non-volatile level may be used in the present invention, provided the polymer dispersion is within the defined viscosity limits. Airless spray technology allows dispersions to be sprayed at higher solids levels than conventional spray techniques. Most commercial polymer dispersions, having solids level of from 40 to 70 percent, may be used without the need for dilution.
Other polymer parameters may be adjusted, as known in the art, to achieve the desired enduse properties. The molecular weight and Tg of the polymer can be varied as desired. Cross-linking and self-cross-linking functionality may be added to the polymer. The hydrophobicity/hydrophilicity of the polymer may be adjusted to achieve the desired level of water resistance.
The polymer dispersion may contain other components, including fillers, whitening and opacity agents, odor control agents such as zeolites, slow release fragrances, flame retardants, and antimicrobial agents.
In one preferred embodiment, titanium dioxide is associated with the dispersion. It is advantageous to apply the titanium dioxide at as high a solids level as possible, and the present invention allows for high solids application. The titanium dioxide is combined with the polymer dispersion at a level of from 5 to 40 percent based on the polymer solids content of the dispersion. The titanium dioxide is stabilized in the dispersion by means known in the art, such as through the use of colloids (including cellulosics), and/or surfactants. Preferably the titanium dioxide will have a particle size of between 0.1 microns and 2.5 microns, most preferably 0.15 to 0.5 microns. The polymer/titanium dioxide dispersion is then sprayed onto a non-woven material using the airless spray technique of the present invention. This process has the advantage of placing titanium dioxide onto the surface of the non-woven where it is most useful, and binding it to the non-woven by the polymer in a manner which prevents its release, or dusting.
The process of the present invention allows for the delivery of the polymer dispersion precisely where neededxe2x80x94either in a complete fiber covering operation, on the surface, or other location. Since a higher-solids dispersion can be used in an airless spray process, a through and through process requires less drying timexe2x80x94thereby improving line efficiency. The main advantage of the present process is the ability to selectively apply a polymer dispersion on a substrate surface. Distribution of the polymer dispersion into the core of a non-woven can be controlled by systematically diluting the dispersion with water.
The process of the present invention can be used in any application in which a polymer dispersion is optimally applied in a precise manner. The process is useful on any known substrate. Because the polymer dispersion can be sprayed at a high solids level, the process is particularly useful with porous material where a surface-only application is desired. Since the polymer dispersion can be sprayed at higher solids level and viscosity, penetration of the substrate can be minimizedxe2x80x94resulting in the use of less polymer, and requiring less time, energy, and expense in drying. Porous materials for which the process is useful include wood, leather, fabrics, textiles, paper, tissue, wadding, and especially non-woven materials. Airless spray is also useful in the preparation of laminate structures, typically being constructed from a variety of porous and non porous substrates (e.g. polyethylene) laminated together with accurately applied layers of polymer dispersion between the various components.
The process of the present invention is useful for forming non-woven materials that typically require consolidation, or the inclusion of binder within the configuration to control dusting or effect specialized surface treatments. The non-woven material may include top-sheets, backing, wipes, tabletop articles (e.g. serviettes), fiber-fill, structures used in hygiene products, and wadding. In a wadding operation, it is desirable to have bonding only at the surface. The wadding process often uses a thermal bonding process, which can be performed at relatively high line speed. Conventional polymer resin-binding operations tend to be slower, since water must be evaporated to form the bond, and since conventional spray techniques cannot precisely apply the binder only to the surface without also going through the surface and into the wadding material. This wastes binder, and requires extra drying time. The process of the present invention allows for faster line speed in a resin-bonded operation, since the binder can be applied only to the surface where it is needed, and can be applied at a higher solids contentxe2x80x94requiring less time and expense for evaporation of water.
A Resin Bonded Airlaid (RBAL) application, typically consists of fluff pulp consolidated with a water based polymer dispersion (e.g. self cross-linking copolymers of Vinyl Acetate Ethylene) in ratios of dry binder to pulp ranging from 5:95 to 40:60, including any combinations between these specified ranges. The binder is applied in the wet state using airless spray technology, with the dispersion being diluted to about 15 percent non volatile content prior to application to assist in the homogenous distribution of binder throughout the fibre matrix. Representative web grammage produced in the bonded nonwoven could vary between 30 and 300 grammes per square meter (gsm).
In a Multi Bonded Airlaid (MBAL) application, the binder is primarily used to control linting (dusting) in the final article . The polymer dispersion would be applied to the web at a non volatile content of 30 weight percent using airless spray to position the binder primarily on the web surface with marginal penetration into the core. The web typically used would consist of fluff pulp plus low melting bicomponent fibres and binder applied on both surfaces. The components could vary according to the following illustrative ratios depending on the grammage of the final product: a) Pulp: Bicomponent: Binder (70:25:5) in an 80 gsm configuration; b) Pulp: Bicomponent: Binder (86:10:4) in a 250 gsm configuration.
A polymer dispersion can be surface coated onto a non-woven web, the web consisting of either purely synthetic fibres, natural fibres, or a combination of both. The binder would be applied to the surface using airless spray technology with the dispersion used as supplied (without dilution), typically about 50 percent non volatile. This limits penetration of the binder into the core, producing in effect a surface coating. The binders used could any polymers known in the art and may have added functionality e.g. antimicrobial, very hydrophilic and very hydrophobic types. The latter two examples of which could be applied on alternate sides of the web in the control of fluid management.

Precision polymer dispersion application by airless spray

National Starch and Chemical Investment Holding Corporation


Stabilized alumoxane solutions are provided as well as a method for producing such solutions. The method generally involves the use of metallocene catalyst component(s) that when mixed with alumoxane solutions reduce the tendency for such solutions to form gels.

This invention relates to a method for producing stabilized alumoxane solutions that are resistant to gel formation. Specifically, the method relates to the use of metallocene catalyst components which, when combined with alumoxane solutions, have the effect of stabilizing such solutions by prolonging the time it takes to form gels.
Alumoxane is commonly used as an activator for metallocene catalyst components in the formation of metallocene catalyst systems. A well-known problem associated with alumoxane solutions is the formation of gel or gel-like particles in the solutions as they age. Typically the alumoxane solution will become more and more viscous until the solution completely gels. This typically occurs over a matter of weeks. More concentrated alumoxane solutions form gels more quickly.
The formation of gels in alumoxane solutions creates many serious problems. For example, it is difficult to transfer such solutions through a line. It is also difficult to effectively combine gelled alumoxane solutions with other substances and catalyst systems made with such solutions tend to have lower activity and have been shown to cause increased reactor fouling tendency when used in olefin polymerization.
Gel formation is believed to be associated with continued reaction leading to increased molecular weight of the oligomeric alumoxane structure. Many methods for reducing gel formation have been described. Refrigeration has been shown to reduce the rate of gel formation, however, refrigeration is quite costly. Vigorous shaking of a gelled alumoxane solution temporarily disperses the gels. Gels can partially be removed by decanting the solution. Unfortunately, these methods not only involve extra effort but are not entirely effective.
A number of methods for preparing gel-free or reduced gel alumoxane solutions have been described. For example, U.S. Pat. No. 5,157,137 describes a method of making alumoxane wherein the alumoxane solution is treated with an anhydrous salt and/or hydroxide of an alkali or alkaline earth metal. It is reported that alumoxane solutions made in this way remain gel free for an extended period of time. U.S. Pat. No. 5,235,081 describes a method of removing gels from alumoxane by mixing an aromatic hydrocarbon solvent of the alumoxane with an aliphatic hydrocarbon solvent and then separating the precipitated solids from the alumoxane solution. U.S. Pat. No. 5,371,260 describes the use of primary or secondary amines with subsequent heat and filtration to prepare gel-free alumoxane solutions. U.S. Pat. No. 5,416,229 describes the use of certain electron-rich heteroatom compounds to stabilize alumoxane solutions and reduce gel formation. While these methods may be somewhat effective, it has been found that some catalyst systems made using such stabilized alumoxanes exhibit inferior performance.
The present inventors have found that by adding metallocene to an alumoxane solution, the alumoxane solution surprisingly remains gel free for an extended period of time. Such solutions may be successfully used to prepare catalyst systems that are highly active and that do not cause extensive fouling of the polymerization reactor when used to polymerize olefins.
This invention relates to a method for stabilizing alumoxane, said method comprising the steps of: (a) combining a metallocene catalyst component with a solution of alumoxane thereby forming a stabilized alumoxane solution; and (b) aging the stabilized alumoxane solution for a time period of at least 24 hours. This invention further relates to a method for producing a catalyst system wherein the stabilized alumoxane produced by the method described above is combined with an additional amount metallocene and optionally a porous support material. There is also provided a method for polymerizing olefins comprising contacting the catalyst system described above with olefin monomer(s) under conditions of polymerization.
Generally, the method of the invention involves simply adding one or more metallocene catalyst component to a solution of alumoxane. The resulting stabilized solution may then be aged for a period of time without forming a substantial amount of gels. This period of time may extend up to 5 years or more. Preferably this period of time is greater than 24 hours, more preferably from 24 hours to 5 years, even more preferably from 2 days to 3 years, even more preferably from 1 to 12 months.
As used herein, xe2x80x9cagingxe2x80x9d simply means allowed to sit without being used as a catalyst system or component. During the aging process, a precipitate may form. This precipitate may be dispersed by stirring or shaking or may be easily filtered from the solution.
Preferably the alumoxane solution to which the metallocene is added is fresh. As used herein the terms xe2x80x9cfreshxe2x80x9d and xe2x80x9cfreshly preparedxe2x80x9d when referring to alumoxane means that the alumoxane is not more than four weeks old (i. e., not more than four weeks have passed from the time of preparation), preferably not more than two weeks old, more preferably not more than 1 week old, most preferably not more than 3 days old.
The stability of an alumoxane solution will depend to some extent on its concentration. The more concentrated the solution, the more quickly the solution will gel. Conversely, a less concentrated solution such as a 10 weight percent or less solution, will remain gel-free for a longer period of time.
The alumoxane solutions useful in the practice of this invention are preferably 5 to 50 weight percent alumoxane solutions, more preferably, the weight percent is in the range of from 10 to 30 weight percent methylalumoxane solutions. Methylalumoxane is the preferred alumoxane. These solutions may be prepared by methods well known in the art or conveniently obtained from commercial sources.
Alkylalumoxanes are thought to contain about 4 to 20 of the repeating units:
where R is a C1-C8 alkyl including mixed alkyls. Particularly preferred are the compounds where R is methyl. There are a variety of methods for preparing alumoxane, non-limiting examples of which are described in U.S. Pat. No. 4,665,208, 4,952,540, 5,091,352, 5,206,199, 5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827, 5,308,815, 5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031 and EP-A-0 561 476, EP-B1-0 279 586, EP-A-0 594-218 and WO 94/10180, all of which are fully incorporated herein by reference.
The amount of metallocene added to the alumoxane solution may vary widely but preferably the molar ratio of the aluminum of the alumoxane to the transition metal of the metallocene is preferably in the range of from about 1000:1 to about 10:1, preferably about 500:1 to about 25:1, even more preferably about 200:1 to about 50:1 and most preferably about 150:1 to about 50:1.
The metallocene may be added as a solution in an aromatic solvent such as toluene or as a solid at any temperature. Preferably the mixture is stirred thoroughly until all solids are dissolved.
Any metallocene may be used in the practice of the invention. Metallocenes are typically those bulky ligand transition metal compounds derivable from the formula:
[L]mM[A]n
where L is a bulky ligand; A is leaving group, M is a transition metal and m and n are such that the total ligand valency corresponds to the transition metal valency. Preferably the catalyst is four co-ordinate such that the compound is ionizable to a 1+ charge state.
The ligands L and A may be bridged to each other, and if two ligands L and/or A are present they may be bridged. The metallocene compound may be full-sandwich compounds having two or more ligands L which may be cyclopentadienyl ligands or cyclopentadiene derived ligands or half-sandwich compounds having one ligand L, which is a cyclopentadienyl Ligand or derived ligand.
Metallocene compounds generally contain a multiplicity of bonded atoms, preferably carbon atoms, and typically contain a cyclic structure such as, for example, a cyclopentadienyl ligand, substituted or unsubstituted, or cyclopentadienyl derived ligand or any other ligand capable of xcex7-5 bonding to the transition metal atom. One or more bulky ligands may be xcfx80-bonded to the transition metal atom. The transition metal atom may be a Group 4, 5 or 6 transition metal and/or a metal from the lanthanide and actinide series. Other ligands may be bonded to the transition metal, such as a leaving group, such as but not limited to hydrocarbyl, hydrogen or any other univalent anionic ligand. Non-limiting examples of metallocene components and catalyst systems are discussed in for example, U.S. Pat. Nos. 4,530,914, 4,952,716, 5,124,418, 4,808,561, 4,897,455, 5,278,119, 5,304,614 each of which is herein fully incorporated by reference. Also, the disclosures of EP-A- 0129,368, EP-A-0520732, EP-A-0420436, WO 91/04257 WO 92/00333, WO 93/08221, and WO 93/08199 are each fully incorporated herein by reference.
The development of metallocene catalyst systems in the art for the polymerization of alpha olefins is illustrated in the disclosures of U.S. Pat. No. 4,871,705 to Hoel, U.S. Pat. No. 4,937,299 to Ewen, et al., 5,324,800 (U.S. application Ser. No. 07/752,415, filed Aug. 30, 1991) and EP-A-0 129 368 published Jul. 26, 1989, and U.S. Pat. Nos. 5,017,714 and 5,120,867 to Welborn, Jr. each of which is fully incorporated herein by reference.
Further, the metallocene catalyst component of the invention can be a monocyclopentadienyl heteroatom containing compound. This heteroatom is activated by either an alumoxane, an ionizing activator, a Lewis acid or a combination thereof to form an active polymerization catalyst system. These types of catalyst systems are described in, for example, PCT International Publication WO 92/00333, WO 94/07928, and WO 91/ 04257, WO 94/03506, U.S. Pat. Nos. 5,057,475, 5,096,867, 5,055,438, 5,198,401, 5,227,440 and 5,264,405 and EP-A-0 420 436, all of which are fully incorporated herein by reference. In addition, the metallocene catalysts useful in this invention can include non-cyclopentadienyl catalyst components, or ancillary ligands such as boroles or carbollides in combination with a transition metal.
The preferred transition metal component of the catalyst system of the invention are those of Group 4, particularly, zirconium, titanium and hafnium. The transition metal may be in any oxidation state, preferably +3 or +4 or a mixture thereof. All the catalyst systems of the invention may be, optionally, prepolymerized or used in conjunction with an additive or scavenging component to enhance catalytic productivity, see for example PCT publication WO 94/07927 incorporated herein by reference.
In one embodiment the metallocene catalyst component is represented by the general formula (Cp)mMeRnRxe2x80x2p wherein at least one Cp is an unsubstituted or, preferably, a substituted cyclopentadienyl ring symmetrical or unsymetrically substituted; Me is a Group 4, 5 or 6 transition metal; R and Rxe2x80x2 are independently selected halogen, hydrocarbyl group, or hydrocarboxyl groups having 1-20 carbon atoms or combinations thereof; m=1xe2x88x923, n=0xe2x88x923, p=0xe2x88x923, and the sum of m+n+p equals the oxidation state of Me.
In another embodiment the metallocene catalyst component is represented by the formulas:
(C5Rxe2x80x2m)pRxe2x80x3s(C5Rxe2x80x2m)MeQ3-p-x and
Rxe2x80x3s(C5Rxe2x80x2m)2MeQxe2x80x2
wherein Me is a Group 4, 5, 6 transition metal, at least one C5Rxe2x80x2m is a substituted cyclopentadienyl, each Rxe2x80x2, which can be the same or different is hydrogen, alkyl, alkenyl, aryl, alkylaryl or arylalkyl radical having from 1 to 20 carbon atoms or two carbon atoms joined together to form a part of a substituted or unsubstituted ring or rings having 4 to 20 carbon atoms, Rxe2x80x3 is one or more of or a combination of a carbon, a germanium, a silicon, a phosphorous or a nitrogen atom containing radical bridging two (C5Rxe2x80x2m) rings, or bridging one (C5Rxe2x80x2m) ring back to Me, when p=0 and x=1 otherwise xe2x80x9cxxe2x80x9d is always equal to 0, each Q which can be the same or different is an aryl, alkyl, alkenyl, alkylaryl, or arylalkyl radical having from 1 to 20 carbon atoms, halogen, or alkoxides, Qxe2x80x2 is an alkylidene radical having from 1-20 carbon atoms, s is 0 or 1 and when s is 0, m is 5 and p is 0, 1 or 2 and when s is 1, m is 4 and p is 1.
Preferred metallocene catalyst components are those selected from the group consisting of bis(cyclopentadienyl) metal dihalides, bis(cyclopentadienyl) metal monoalkyl monohalides, bis(cyclopentadienyl) metal dihalides, bis(indenyl) metal dihalides, bis(indenyl) metal dialkyls and their ring-substituted analogs. Preferred metals are those selected from the group consisting of Ti, Zr, Cr and Hf. Preferred halides are those selected from the group consisting of Cl, Br, and F, with Cl being particularly preferred. Particularly preferred metallocenes are those selected from the group consisting of bis(cyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)zirconium dimethyl, bis(pentamethylcyclopentadienyl)zirconi um dichloride, bis(pentamethylcyclopentadienyl)zirconium dimethyl, bis(pentamethylcyclopentadienyl)hafnium dichloride, bis(pentamethylcyclopentadienyl)zirconium dimethyl, bis(1-methyl-3-n-butylcyclopentadienyl)zirconium dichloride, bis(1-methyl-3-n-butylcyclopentadienyl)zirconium dimethyl, bis(1-methyl-3-n-butylcyclopentadienyl)hafnium dichloride, and bis(1-methyl-3-n-butylcyclopentadienyl)zirconium dimethyl.
After the stabilized alumoxane is aged, it may be used in at least one of two ways. First, the alumoxane may be used directly as an active catalyst system. Second, additional metallocene may be added to the aged alumoxane before use as an active catalyst system. If additional metallocene catalyst component is added, preferably, the metallocene and aged alumoxane are combined first prior to charging to the polymerization reactor. It is also preferable to combine the metallocene(s) and aged alumoxane with a support material prior to charging to the reactor. The metallocene may be applied to the support before application of the aged alumoxane or, conversely, the aged alumoxane may be applied first to the support followed by the metallocene. Alternatively, and preferably, the metallocene and aged alumoxane are combined first then applied to the support material.
The mole ratio of the aluminum of the aged alumoxane component to the total of the metallocene component(s) is preferably in the range of ratios between 0.3:1 to 1000:1, preferably 20:1 to 800:1, and most preferably 50:1 to 500:1.
Examples of supporting the catalyst system used in the invention are described in U.S. Pat. Nos. 4,937,217, 4,912,075, 4,935,397, 4,937,301, 4,914,253, 5,008,228, 5,086,025, 5,147,949, 4,808,561, 4,897,455, 4,701,432, 5,238,892, 5,240,894, 5,332,706 and U.S. patent application Ser. Nos. 138,818, filed Oct. 14, 1993, 170,108, filed Dec. 20, 1993, 182,244, filed Jan. 14, 1994,233,668, filed Apr. 26, 1994, 265,533, filed Jun. 24, 1994, 265,532, filed Jun. 24, 1994, 271,598, filed Jul. 7, 1994, 287,322, filed Aug. 8, 1994, 285,380, filed Aug. 3, 1994 and PCT Publication WO 93/11172, all of which are herein incorporated by reference.
The catalyst system of this invention is suited for the polymerization of monomers, optionally with at least one comonomer in any polymerization or prepolymerization process, gas, slurry or solution phase or a high pressure autoclave process. In the preferred embodiment a gas phase or slurry phase process is utilized.
Typically in a gas phase polymerization process a continuous cycle is employed wherein one part of the cycle of a reactor, a cycling gas stream, otherwise known as a recycle stream or fluidizing medium, is heated in the reactor by the heat of polymerization. The recycle stream usually contains one or more monomers continuously cycled through a fluidized bed in the presence of a catalyst under reactive conditions. This heat is removed in another part of the process by a cooling system external to the reactor. The recycle stream is withdrawn from the fluidized bed, cooled, and recycled back into the reactor. Simultaneously, polymer product is withdrawn from the reactor and new or fresh monomer and catalyst is added to replace the polymerized monomer and consumed catalyst. See for example U.S. Pat. Nos. 4,543,399, 4,588,790, 5,028,670, 5,382,638 and 5,352,749, 5,405,922, U.S. application Ser. No. 08/306,055 filed Sep. 14, 1994 and U.S. application Ser. No. 08/317,136, filed Oct. 3, 1994 and PCT patent application WO 94/28032 published Dec. 8, 1994 all of which are fully incorporated herein by reference.
In one embodiment, the invention is directed toward a polymerization process involving the polymerization of one or more of the monomer(s) including ethylene alone or in combination with one or more linear or branched monomer(s) having from 3 to 20 carbon atoms, preferably 3 to 12 carbon atoms. The process is particularly well suited for copolymerization reactions involving the polymerization of ethylene in combination with one or more monomers such as propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, styrene and cyclic and polycyclic olefins such as cyclopentene, norbornene and cyclohexene or a combination thereof. Other monomers for use with ethylene may include polar vinyl monomers, diolefins such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, norbomene, norbomadiene, and other unsaturated monomers including acetylene, 1-alkynes and aldehyde monomers. Higher alpha-olefins and polyenes or macromers may be used also. Preferably the comonomer is an alpha-olefin having from 3 to 15 carbon atoms, preferably 4 to 12 carbon atoms and most preferably 4 to 10 carbon atoms.
In another embodiment ethylene is polymerized with at least two different comonomers to form a terpolymer and the like, the preferred comonomers are a combination of alpha-olefin monomers having 3 to 10 carbon atoms, more preferably 3 to 8 carbon atoms, optionally with at least one diene monomer. The preferred terpolymers include the combinations such as ethylene/butene-1/hexene-1, ethylene/propylene/butene-1, ethylenelpropylene/hexene-1, ethylene/propylene/norbornadiene, ethylene/propylene/1,4-hexadiene and the like.
In one embodiment a scavenger may be used, however, in another preferred embodiment, the process of the invention does not require a scavenger, non-limiting examples of scavenger compounds include for example, triethylaluminum (TEAL), trimethylaluminum (TMAL), tri-isobutylaluminum (TIBAL), tri-n-hexylaluminum (TNHAL), diethyl aluminum chloride (DEAC) and the like.
In another embodiment of the process of the invention an inert hydrocarbon component or antistatic agent as described in U.S. Pat. No. 5,238,278 and U.S. application Ser. No. 08/322,675, filed Oct. 13, 1994 can be introduced into the reactor together, separately or apart, from the catalyst system of the invention.
A slurry polymerization process generally involves pressures in the range of about 1 to about 500 atmospheres or even greater and temperatures in the range of xe2x88x9260xc2x0 C. to about 280xc2x0 C. In a slurry polymerization, a suspension of solid, particulate polymer is formed in a liquid polymerization medium to which ethylene and comonomers and often hydrogen along with catalyst are added. The liquid employed in the polymerization medium can be alkane or cycloalkane, or an aromatic hydrocarbon such as toluene, isobutylene, ethylbenzene or xylene. The medium employed should be liquid under the conditions of polymerization and relatively inert. Preferably, hexane or isobutane is employed. A non-limiting example of a slurry process can be found in PCT Publication WO 94/21691, published Sep. 29, 1994 which is herein fully incorporated by reference.


A formulation which promotes gum and oral health through the presence of natural components exhibiting astringent, antiseptic and local stimulant effects. The formulation can be in the form of a concentrate, an oral rinse, gel, ointment, and other topical forms. The formulation also promotes healing of sores and wounds as well as preventing toothdecay. The use of cayenne as a preferred component has a synergistic effect on other components effects.

This invention pertains to compositions and their method of use in the maintenance and improvement of oral health, more specifically, a formulation of herbal extracts and essential oils, known by herbal health authorities to possess desired beneficial effects, which in combination provide a synergistic effect on the improvement and maintenance of gum and oral health.
Gum disease and oral health problems have reached epidemic proportions. According to the American Dental Association, three out of four adults over the age of 35 have some form of gum disease. Recently, the Surgeon General issued a report on oral health.
Studies have shown that gum (periodontal) disease not only can cause the loss of teeth, but can cause much more serious diseases. Individuals with gum disease have been shown to have an increased incidence of heart disease, diabetes, and respiratory disease and have increased risk of stroke, increased buildup of plaque in carotid arteries, weakened immune systems and increased risk of complications from diabetes.
Treatment of gum disease by a periodontist usually is scaling and planning to remove hidden plaque and tartar below the gum line. In addition, in severe cases of gum disease, the diseased portions of the gums are surgically removed one quadrant at a time, and can potentially require the removal of teeth. These procedures are painful, expensive and merely treat the symptoms of the disease.
Many substances have been used individually and in combinations to improve gum and oral health. It would be highly desirable to combine the substances for optimal improvement of gum and oral health. The solution disclosed herein not only provides optimal improvement of gum and oral health, but also provides for prevention of gum and oral health problems.
A formulation is disclosed which provides optimal improvement of gum and oral health and provide for the prevention of gum and oral health problems. The invention uses a unique combination of ingredients which exhibit desired properties including antiseptic, astringent, stimulant and local analgesic properties, which in the present formulations result in the synergistic properties of all the components. The use of capsicum in the formulation has demonstrated remarkable synergistic, almost catalytic, effect with the other components of the formulation. A preferred formulation is prepared in a concentrated form. Typical use of the concentrate, uses a diluted solution of the concentrate as an oral irrigator or mouth wash which bolsters maximum penetration into gum pockets. The concentration of the solution can be varied to achieve desired results. The concentrate can also be formulated into a toothpaste, oral gel, poultice, paste, salve, and the like. In additional to helping minimize gum disease, the formulations have been shown to aid in the reduction in the formation of cavities and also promotes the healing of cold sores and wounds.
To achieve the desired results, the preferred formulation exhibits astringent, antiseptic (for example antibacterial, antifungal, bactericidal, and virucidal), local stimulant, anti-inflammatory, immuno-stimulant and local analgesic properties. These properties can be attained by using a combination of components, wherein each component exhibits one or more of the desired properties. The formulation can contain more than one component which exhibits the same desired property.
For ease of production, preferred components are in the form of a liquid, such as fluid extracts, tinctures, solid extracts, and the like, but can also be in the form of powders and the like. To promote health and ensure safety, it is also desirable that the components be extracts, oils, powders, etc., of naturally occurring flora and that these components are not chemically processed other than the process used to directly produce the fluid extract, tincture or oil, and are thereby suitable for use in the oral cavity.
Examples of preferred astringents include, but are not limited to, bayberry bark, white oak bark, rhatany bark, sage, and teas,.
Examples of antiseptics include, but are not limited to peppermint oil, Echinacea, bloodroot, cayenne, tea tree oil, wild bergamont, chaparral, stinging metal, bay, myrrh, rhatany bark, toothache tree, calendula, and chamomile.
Examples of local stimulants include, but are not limited to, cayenne, peppermint oil, calendula, wintergreen, bayberry, and sage.
It is contemplated that additional components may include coloring and flavoring additives. As an example of multi-property components, the use of peppermint oil takes advantage of the local stimulant and antiseptic properties as well as providing a flavoring component.
Preferred formulation s include cayenne to utilize its multiple desirable properties and its synergistic effect on the properties of other components in the formulation.
A preferred formulation is comprised of echinacea, bloodroot, bayberry, white oak bark, cayenne, tea tree oil, and peppermint oil. The echinacea provides antiseptic (antibacterial) and local analgesia as well as exhibiting some boost to the immune system. The bloodroot provides an antiseptic effect and prevents the formation of plaques from bacteria, most likely through the presents of the antiseptic sanguinarine which prevents several types of oral bacteria from forming dental plaque. The bayberry tightens gums and provides antiseptic, astringent and local stimulant effects. The white oak bark also tightens gums and provides astringent, antiseptic and anti-inflammatory effects. The cayenne acts as an antibacterial, stimulates circulation, blocks pain, and also supplies a synergistic effect on the effects of the other components in the formulation. The tea tree oil provides antiseptic (antibacterial) and anti-inflammatory effects. The peppermint oil stimulates circulation, provides antiseptic effects and acts as a flavoring agent and breath freshener.
A preferred formulation is comprised of
Another preferred formulation for the composition is comprised of
The above formulations result in a concentrate which can be used in any number of application methods, formulations and compositions. For example, the concentrate can be diluted with water and used as a mouthwash. A preferred rinse comprises up to 5% by volume of the concentrate diluted with purified water. The concentrate could be impregnated in or coated on a dental floss or fibers of a toothbrush. The concentrate can also be added to a toothpaste base, oral gel, or other oral compositions. The concentrate can also be used by placing 1-2 drops directly on a toothbrush or on commercially available toothpaste and used to brush the teeth and gums.
After application, for example by rinsing, brushing, or application of a gel, or the like, it is preferable that the mouth is not rinsed, however; rinsing after use, as for example if used in or with a toothpaste, will not dramatically reduce the effectiveness of the composition.
The concentrate can also be applied directly, or with some suitable carrier, to cold sores (chancre sores) in or around the mouth. The concentrate provides pain relief and also promotes the healing of the sore.
The concentrate can also be applied directly, or with a suitable carrier, to wounds, including lacerations, incisions, surgical incisions, etc., to provide pain relief and the promotion of healing, as well as antiseptic. The concentrate also appears to reduce the formation of scar tissue in/on such wounds.
The following examples are provided for illustrative purposes and are not presented as a limitation on the scope of this invention.

Oral hygiene formulation and method of use


A method is described for automatically and accurately defining tissue borders within ultrasound imaging. A preferred embodiment described provides for accurately delineating endocardial and epicardial tissue borders during ultrasound imaging of the heart using contrast agents. The inventive method requires first defining a set of threshold values corresponding to various imaging depths and correlated within the image. The invention further uses the set of threshold values and a maximization function to accurately identify the tissue boundaries.

This invention relates to ultrasonic diagnostic imaging systems and, in particular, to ultrasonic diagnostic imaging systems, which utilize adaptive processing of contrast-enhanced ultrasound images to accurately and/or automatically detect and define tissue boundaries.
Conventional ultrasound diagnostic imaging procedures, which quantify bodily structures and functions, rely upon an assumption that the acquired ultrasound data will clearly delineate and define tissue boundaries. When the quantification or measurement procedure uses static images or a small set of measurements, the delineation of the bodily structure may be measured manually. An example of such a procedure is the obstetrical measurements of a developing fetus. The static images of the developing fetus must be acquired during periods when fetal activity is low. Once an image is acquired, only a few circumference or length measurements are usually required to compute development characteristics such as gestational age and anticipated delivery date from the static images. These measurements can readily be made manually on the fetal images. Manual measurements, however, may be time consuming and subjective.
Other diagnostic imaging procedures, particularly those involving movement in and/or around the object being imaged, for example, taking measurements of the heart and its functioning (e.g., ejection fraction), are much more complicated than simply measuring static images. The heart is always beating and hence tissue and blood are always in motion. More particularly, as the heart contracts and expands (relaxes) to pump blood, its contours (endocardial and epicardial boundaries) constantly move and change with respect to image space. To fully assess many characteristics of cardiac function, it is necessary to evaluate many, and at times all, of the images acquired during the heart cycle (one heartbeat). This may amount to thirty to one hundred and fifty or more images. Cardiac structures of interest, such as the endocardium, epicardium or valves, must then be delineated in each of the images. The constant cardiac motion causes the structures to appear slightly different in each image or frame acquired during the cardiac cycle. This is a painstaking, time-consuming task for a technician. And while ultrasonic contrast agent injected into the blood provides for delineating between myocardium and vascular pathways, contrast agent is nevertheless a strong attenuator of ultrasound energy, which under certain circumstances leads to blurring of tissue boundaries and inaccurate interpretation of cardiac function.
The state of the art of ultrasound imaging and diagnosis, including but not limited to cardiac and vascular imaging and diagnostics, would readily benefit from an improved and/or automatic process for more clearly delineating specific anatomy and tissue boundaries. Quantification of cardiac function often relies on the delineation of structure or tissue boundaries as an input. For example, myocardial wall thickening is currently assessed in stress-echocardiographic exams, where, for example, the actual size of the ventricle is measured and diagnosis is based on such measurement. The degree of wall thickening is typically qualitatively scored by the clinician conducting the stress test without the use of measurement tools because (as mentioned above) segmental measurements over the cardiac cycle are too time-consuming. This leads to inaccuracies and misdiagnosis. Moreover, techniques for assessing blood perfusion information using contrast agents or Doppler techniques which rely upon conventional processes and techniques for delineating cardiac borders are also inaccurate at times.
Research into systems that automatically analyze ultrasound images and draw borders around objects in the images has been underway for over a decade. Progress is at times impeded by the inherent specular nature of and speckle noise within ultrasound images, as well as the variability with which tissue structures may appear in an image. Many conventional systems use assisted or semi-automatic approaches, which require that the user manually mark key reference points in an image, or draw a complete border of an object in one image. The inputs are then used as references from which the balance of a border or other borders will be drawn. This need for user input limits semi-automatic techniques to operating only with stored images and prevents their use in real time.
Several prior art writings which may provide a flavor of the issues involved in ultrasound imaging of cardiac borders include Wilson, et al., Automated Vessel Analysis Of Echocardiographic Apical 4-Chamber Images; DEPT. OF MATHMATICS, UNIVERSITY OF FLORIDA, Gainesville, Fla. 32611, SPIE, August, 2000; Hozumi, et al., Echocardiographic Estimation Of Left Ventricular Cavity Area With a Newly Developed Automated Contour Tracking Method, American Society of Echocardiography, October 1997, pgs. 822-829; Mignotte, et al., Endocardial Boundary Estimation And Tracking In Echocardiographic Images Using Deformable Templates And Markov Random Fields, Pattern Analysis & Applications (2001), 4:256-271.
An automatic border detection (ABD) system which reliably delineates the border of an object in an ultrasound image without user preconditioning, and in real time is found in U.S. patent application Ser. No. 09/732,613. The application is commonly owned with the owner hereof, and its disclosure is incorporated herein by reference in its entirety. The inventive content shall be referred to hereinafter as "Philips ABD inventions." The Philips ABD inventions teach techniques for automatically, and with user input, delineating the border or boundary of an object by locating key landmarks of the ultrasound image of the object. After locating the key landmarks in the ultrasound image data, the inventive processes fit one of a plurality of predefined standard shapes to the landmarks and object. In one particular embodiment of the Philips ABD inventions, an ultrasound system is disclosed which displays both the end systole and end diastole images of a cardiac cycle, and automatically draws borders on both images.
Prior art FIG. 1 herein corresponds to the Philips ABD inventions. More particularly, FIG. 1 shows an ultrasound image 10 which is one of a sequence of an apical four-chamber view of the heart, which was acquired by a phased array transducer probe. The prior art acquisition process requires that the probe is oriented to view the heart from the proximity of its apex 11. The largest chamber in the image (the central and upper right portion of the image) is the left ventricle (LV). As the real-time ultrasound image sequence is acquired, an ECG trace 12 of the heart cycle is simultaneously acquired and displayed at the bottom of the display. Triangular marker 14 denotes the point or phase of the cardiac cycle at which the currently displayed image was acquired.
As the user views the display of FIG. 1, the heart is seen beating in real time as the ECG waveform 12 scrolls beneath the ultrasound images 10. The instantaneously displayed heart phase is indicated by the marker 14. A typical duration of the heart cycle when the body is at rest is about one second. Imaging of one cycle consequently requires acquiring and displaying approximately 30-90 image frames. Clinicians often acquire and save the sequence of images of a heart cycle and then replay them (in a continuous "loop"), repetitively displaying the selected cardiac cycle.
When the protocol of the FIG. 1 embodiment of the Philips ABD inventions is actuated, the display changes to a dual display. The process is highlighted in prior art FIG. 2, where an end diastole image 16, and end systole image 18 are displayed side-by-side. The protocol also recognizes the end diastole and end systole points of the cardiac cycle in relation to the R-wave of the ECG waveform 12. That is, the ECG waveform R-wave is used to identify and display the ultrasound images at these two phases of the heart cycle. The dual display of prior art FIG. 2 shows the ECG waveform 12 for the selected heart cycle beneath each ultrasound image. Marker 14 indicates the end diastole and end systole phases at which the two displayed images were acquired.
The protocol further provides that the ABD-driven processor first draws the endocardial border of the LV in the end systole image 18 of prior art FIG. 3A. The first step in drawing the border of the LV requires locating three key landmarks in the image, the medial mitral annulus (MMA), the lateral mitral annulus (LMA), and the endocardial apex. Defining a search area 24 for the MMA (as shown in FIG. 3A) begins the process of locating. The ABD-driven processor is preconditioned to analyze four-chamber views of the heart with the transducer 20 from its apex. Consequently, it expects the brightest vertical near field structure in the center of the image to be the septum 22. This means that the column of pixels in the image with the greatest total brightness value should define the septum. With these cues, the prior art ABD-driven processor locates the septum 22, and then defines an area in which the MMA should be identified. This area is defined from empirical knowledge of the approximate depth of the mitral valve from the transducer in an apical view of the heart. Search area 24 is defined in this manner.
A filter template defining the anticipated shape of the MMA is then cross-correlated to the pixels in the MMA search area. This template may be created from expert knowledge of the appearance of the MMA in other four-chamber images as used by Wilson, et al., in their paper "Automated analysis of echocardiographic apical 4-chamber images," Proc. of SPIE, August, 2000. For that matter, it appears that any of a geometric corner template, right angle corner template, and octagon corner template may be used as filter templates. For example, an octagon corner template 28 (the lower left corner of an octagon) as their search template for the MMA is shown at the right side of prior art FIG. 4A, where in actual practice, the binary matrix shown at the left side of prior art FIG. 4A represents the octagon template.
The conventional ABD-driven processor performs template matching by cross-correlating different sizes of this template with the pixel data in different translations and rotations until a maximum correlation coefficient above a predetermined threshold is found. To speed up the correlation process, the template matching may initially be performed on a reduced resolution form of the image. This highlights major structures and may be produced by decimating the original image resolution. When an initial match of the template is found, the resolution may be progressively restored to its original quality and the location of the MMA progressively refined by template matching at each resolution level. Once the MMA has been located, a similar search is made for the location of the LMA, as shown in prior art FIG. 3B.
In prior art FIG. 3B, a small box 26 marks the location established for the MMA in the image 18, and a search area to the right of the MMA is defined as indicated by a box 34. A right corner geometric template, preferably a right octagon corner template 38 as shown in prior art FIG. 4B, is matched by cross-correlation to the pixel values in the search area of box 34. Again, the image resolution may be decimated to speed the computational process and different template sizes may be used. The maximal correlation coefficient exceeding a predetermined threshold defines the location of the LMA. With the MMA 26 and the LMA 36 found, the next step in the process is to determine the position of the endocardial apex, which may be determined as shown in prior art FIG. 5.
The pixel values of the upper half of the septum 22 are analyzed to identify the nominal angle of the upper half of the septum, as indicated by the broken line 43. The pixel values of the lateral wall 42 of the LV are analyzed to identify the nominal angle of the upper half of the lateral wall 42, as shown by the broken line 45. If the lateral wall angle cannot be found with confidence, the angle of the scanlines on the right side of the sector is used. A line 48 bisects the angle between the broken lines 43, 45, and the apex is initially assumed to be located at some point on this line. With the horizontal coordinate of the apex defined by line 48, a search is made of the slope of pixel intensity changes along the line 48 to determine the vertical coordinate of the apex. This search is made over a portion of line 48 which is at least a minimum depth and not greater than a maximum depth from the transducer probe, approximately the upper one-quarter of the length of line 48 above the mitral valve plane between the MMA 26 and the LMA 36. Lines of pixels along the line 48 and parallel thereto are examined to find the maximum positive brightness gradient from the LV chamber (where there are substantially no specular reflectors) to the heart wall (where many reflectors are located).
A process for finding a gradient is part of Philips ABD inventions, which may be understood broadly by viewing prior art FIGS. 6A, 6B, and 6C. More particularly, FIG. 6A shows a portion of an ultrasound image including a section of the heart wall 50 represented by the brighter pixels in the image. Drawn normal to the heart wall 50 is a line 48, which, from right to left, extends from the chamber of the LV into and through the heart wall 50. If the pixel values along line 48 are plotted graphically, they would appear as shown by curve 52 in prior art FIG. 6B, in which brighter pixels have greater pixel values. The location of the endocardium is not the peak of the curve 52, which is in the vicinity of the center of the heart wall, but relates to the sense of the slope of the curve. The slope of the curve 52 is therefore analyzed by computing the differential of the curve 52 as shown by the curve 58 in prior art FIG. 6C. This differential curve has a peak 56, which is the maximal negative slope at the outside of the heart wall (the epicardium). The peak 54, which is the first major peak encountered when proceeding from right to left along curve 58, is the maximal positive slope, which is the approximate location of the endocardium. The pixels along and parallel to line 48 in FIG. 6A are analyzed in this manner to find the endocardial wall and hence the location of the endocardial apex, marked by the small box 46 in prior art FIG. 5.
While the Philips ABD inventions do provide a tool for drawing cardiac borders, such prior art systems and processes cannot always be relied upon to identify true endocardial borders. For example, in ultrasound imaging which includes the use of contrast agents, signal energy returning from the contrast agent (reflecting, resonating or bursting microbubbles) is not always homogeneous. That is, returning signals are affected by ultrasound speckle, blood supply, non-uniform bubble destruction, signal attenuation along scanlines, etc. Further, due to speckle, signal loss and variation in the myocardium, applying a simple thresholding technique to the myocardium edge yields only staggered points, which may or may not be linear. Results include borders drawn with edge points that do not fill along the border at all.
It is therefore at least one object of the present invention to provide a method for endocardial and epicardial delineation of the myocardium for use with parametric imaging of cardiac perfusion, and ultrasound system for implementing same.
It is at least another object of the invention to provide a method for endocardial and epicardial delineation of the myocardium for use with parametric imaging of the cardiac perfusion, which utilizes an array of thresholds corresponding to image depth, and ultrasound system for implementing same. Preferably, the imaging depth is determined as a function of a center scanline in an ultrasound cardiac image.
It is at least another object of the invention to provide a method by which endocardial, epicardial and apical edges of the myocardium are approximated by smooth curves, and ultrasound system implementing same. Preferably, the inventions use a maximization function to realize the best fit of threshold-determined points of a polynomial function of degree N, where N is an integer number.
And it is at least another object of the invention to provide an ultrasound imaging method and diagnostic imaging system which shows improved tissue boundary delineation over those methods and system known in the conventional arts, with or without the use of ultrasound contrast agents.
Those skilled in the art should note that while a substantial portion of the disclosure refers particularly to cardiac and contrast-enhanced ultrasound imaging and diagnostics, reference thereto is for exemplary purposes only. The present invention is directed to an improved method for delineating tissue boundaries in general, through the use of the inventive thresholding technique described, and is not limited to cardiac imaging and diagnostics, or other vascular-related imaging and diagnostics.
More particularly, while the prior art for automatic border detection does provide tools for drawing tissue borders, such conventional border detection and delineation systems and processes cannot always be relied upon to identify true tissue borders. This is sometimes the case with Philips ABD inventions as discussed above. More particularly, visual distinction between pixels is at times unclear while using the Philips ABD inventions for a variety of reasons. For example, in contrast agent enhanced ultrasound imaging, signal energy returning from the contrast agent (reflecting, resonating or bursting microbubbles) is not always homogeneous. That is, returning signals are affected by ultrasound speckle, tissue inhomogeneity, blood supply, non-uniform bubble destruction, signal attenuation along scanlines, etc. Further, due to speckle, signal loss and variation in the myocardium, applying a simple thresholding technique to the myocardium edge yields only staggered points, which may or may not be linear. Results include borders drawn with edge points that do not fill along the border at all.
In a preferred embodiment, the present invention overcomes the shortcomings of the conventional arts by generating and utilizing an array of thresholds which are a function of image depth. The array of thresholds is then used to identify endocardial and epicardial borders more accurately than known ABD or ACD methods. That is, once the threshold array is acquired and stored, the orientation of the structure (e.g., heart) with respect to the direction of a center scanline is determined. The center scanline is defined by first automatically (or manually) identifying several landmarks or key points within the image, and using the landmarks to generate center the scanline. Preferably, three (3) key points or landmarks are used. Accurate thresholds are then calculated from the array of thresholds for use at a given depth to combat signal loss or attenuation at the depth when searching for structural edges.
In one implementation, the embodiment may be utilized in cardiac diagnostic imaging. That is, FIG. 7 herein shows a high quality cardiac image with contrast agent in the left ventricular (LV) cavity. While the distinction between the LV cavity and myocardium is generally clear in this figure, swirls may be seen in the LV. A gradual loss of contrast signal toward the mitral level is seen as well, which may at times thwart simple threshold based segmentation. FIG. 8 shows three key points or landmarks already mentioned. The three key points or landmarks may be automatically determined, as described in the Philips prior art ABD inventions, or may be manually input by a user. The three points are shown as white squares in FIG. 8, and define the mitral valve (MMA and LMA) and apex of the LV cavity. A central axis or scanline is drawn between the apical point of the LV cavity and the bisector point of the mitral plane (seen as a vertical scanline in the figure).
The reader should note that the key points or landmarks (e.g., 3) described are identified in particular merely for exemplary purposes. The invention is not limited to these particular three points or even a fixed number of key points. That is, as long as one skilled in the art is able to determine a set of thresholding values which are defined and correlated as a function of image depth and/or quality, any method may be used for defining a point of axis within the image for use as a focal point or landmark. It is the use of the thresholding values which renders the invention unique. Moreover, while the inventions are described in the preferred embodiments for use in cardiac ultrasonic imaging, they are not limited to tissue border detection and delineation within the heart only. The principles set forth herein may be implemented in any ultrasonic imaging process which attempts to delineate tissue boundaries in any organ or vessel, particularly in processes using contrast agents, for example, any perfusion analysis, and for 3-D imaging.
For that matter, the inventions described herein are not limited to two-dimensional planar ultrasound echo images, but may 3-D contrast-enhanced images of the heart or other organs. In 3-D applications, key landmarks and chord projections are extended to the three-dimensional space, and a 3D-contour model is used rather than a polygon approximation the 3-D boundaries of the structure.
The method includes calculating a series of chords in such a manner that the chords project out from the central axis toward the myocardium. In one implementation, the chords may be represented by gray lines in the cardiac image as shown in FIG. 8. The chords therein are arranged to be parallel to the mitral valve plane, and spaced at regular intervals. At the origin of each chord (intersection of gray parallel lines and the central scanline at the central axis), small neighborhoods of pixel intensity values are summed, and the mean of the value is determined by the disclosed method. This is one process for defining a threshold for use herein, where the threshold value is a percentage of the mean value found for each chord. Traveling along a particular chord, starting from the central axis, if the intensity value is determined to fall below the threshold for N consecutive pixels, the area is determined to be an edge (marked by white "X's" in FIG. 8). The method requires repetition of this step in the process for all chords. Because a new threshold is determined for each chord, the process adapts to the local intensity when trying to determine edges.
The present invention also addresses other shortcomings in the art. That is, due to speckle, signal loss, and variation (for example, in the left ventricle and myocardium) applying a simple threshold at the edges of a tissue structure (e.g., the myocardium) yields a series of staggered points. The may be readily seen in FIG. 9 along the edges of the myocardial border. And because prior art thresholding techniques do not consider image morphology, many points do not fall along the actual border at all. To remedy this, the invention provides smooth curves to approximate the edges of a tissue structure being imaged, for example, the endocardial, epicardial and apical edges of the myocardium. The invention does so by fitting the threshold-determined points with a polynomial function of degree N (where N is an integer number), realizing a robust and visually pleasing edge. The inventive approach requires three distinct steps to realize a smooth curve which accurately approximates the tissue edges. The first step requires that a polynomial of degree N be fit through all of the threshold-determined points of a particular edge, for example, left endocardial. The second step requires calculating the mean distance between the polynomial fit and actual threshold-determined points. The third step requires eliminating outlier points which are further than a factor F times (F is an integer value) the mean distance. These second and third steps are iterated until no additional outlying points are illuminated. The result is a robust curve fitting. The result, however, does not provide any information about how well the polynomial fits the actual border.
The invention further provides for determining the best polynomial approximation to the real edges through the use of a maximization function. The required maximization function uses three parameters. The three parameters are the mean intensity along the polynomial, the number of threshold points used to approximate the polynomial and goodness-of-fit parameter (such as the chi-squared error) of the polynomial approximation to the threshold points. FIG. 9 is a cardiac image which shows the inventive polynomial fitting to a series of threshold-determined points which are very far from the scanline or center axis described above. Many of the threshold points, seen as small white x's in FIG. 9, are determined by the inventive process to be outliers. The invention delineates these outliers in the image by marking them as small white filled circles (see FIG. 9). These are marked as filled circles merely to distinguish them from x's because the outliers fall outside the echo sector.
The method of determining the best polynomial, which uses these three parameters, does so iteratively. The threshold values determined along each chord from the central axis are multiplied by a percentage factor, which varies between an upper and lower limit. The polynomial fit and maximization function are calculated for each threshold percentage, and a graph is generated, as shown in FIG. 12. The process is iterated so that one polynomial fit and one maximization function result is generated for each arbitrary step between the upper and lower threshold limits. The maximization function attempts to simultaneously minimize the mean intensity along the polynomial approximation, maximize the number of points used in the polynomial approximation, and minimize the error between the edge points and the polynomial approximation (minimize the chi-squared error). The output of maximization function is graphed per iteration, and a peak in the graph indicates the best polynomial fit at the best threshold (arrow in FIG. 12). Results have shown that such an approach yields maximized polynomial approximation to the real edge in terms of position and border type.
FIG. 10 shows a further iteration of the polynomial fitting process with respect to the image, and its state as shown in FIG. 9. There, the threshold percentage is increased, and the maximization function has achieved a higher value than that which was achieved in the iteration shown in FIG. 9. That is, more points, highlighted by the white x's in the figure, are used for the curve fitting, and the number of outliers (small white filled circles) is significantly decreased. This proves to be a very convenient tool in any tissue border delineation operation, rendering subsequent volume measurements quite routine.
FIG. 11 shows a representation of the FIG. 9 image as the best estimate of the true edge by the inventive process of this invention. The number of points used in the polynomial curve fitting has been maximized, and the mean intensity of the threshold points along the edges has been minimized. Moreover, the chi-squared error between the polynomial approximation and the threshold point is minimized. More to the point, the results of the inventive maximization function are graphically shown in FIG. 12, where the x-axis is the iteration number, with each iteration corresponding to particular threshold percentage, and the y-axis is the value of the maximization function. The peak, as indicated by the arrow in FIG. 12, corresponds to threshold percentage values, which, in turn, yield the best approximation of the edge.
FIG. 13 shows another iteration of the cardiac image as first seen in FIG. 9, where the threshold percentage is too high. The threshold points remain in the left ventricular cavity and the maximization function yields very low values, as can be seen by the right side of the graph in FIG. 12. The trace is fit to the threshold values, marked by the x's in the figures. The trace is fit using a polynomial approximation of degree N, preferably of degree 2, 3, or 4. The higher the degree of the polynomial approximation, the more freedom for curviness for the approximation. The reader should note that it is along the center scanline that the initial estimates of the threshold are made, and that the landmarks are merely setup to create a frame of reference for the final curve fit. The key points or landmarks also set up a "known" geometry that passes through the middle of the object whose edges we want to identify, and create known endpoints for the final curve fit. As mentioned above, while three key points or landmarks are preferred, varying circumstances might require more or less than three key points.
The inventive process described herein can be automated, such that all of the steps described occur with a minimum of user interaction, or may be used interactively, with the clinician to adjust threshold percentage limits to realize optimal tissue border definition, and the increased accuracy of any volumetric quantification occurring subsequently based thereon. The reader should note that the preferred embodiments of the invention as set forth herein are is for exemplary purposes only. The scope of the invention is limited only by the scope and limitations of the claims appended hereto.

Adaptive processing of contrast enhanced ultrasonic diagnostic images


Fluorinated emulsifiers, in particular, perfluorooctanoic acid are bound to anionic exchange resins for the purification of aqueous effluent from the production of fluoropolymers. Said emulsifiers may be quantitatively eluted from the exchanger with a water-miscible organic solvent, containing a small amount of ammonia. It is of advantage to distil off the ammonia containing solvent, recycle the emulsifier to a further polymerization and recycle the ammoniacal solvent for elution. Addition of alkalis improves the elution efficiency.

This application is a 371 national stage application of PCT International Application Serial No. PCT/EP00/10638 filed Oct. 28, 2000 (International Publication Number WO 01/32563, published May 10, 2001), which claims priority to German Application No. 199 53 285.0, filed Nov. 5, 1999.
The invention pertains to a method for eluting fluorinated emulsifiers from anion exchanger resins in a basic environment, which is especially useful for purifying aqueous effluent from the production of fluoropolymers.
Fluoropolymers such as fluoroelastomers, fluorothermoplastics and polytetrafluoroethylene (PTFE) are produced through aqueous radical emulsion polymerization. Emulsion polymerization requires highly fluorinated emulsifiers to ensure satisfactory colloidal stability. The emulsifiers used should not react with the fluoropolymer radicals, and therefore should not be telogenic. Usually used is APFOS, the ammonium salt of perfluorooctanoic acid (PFOS).
The polymerization is followed by the isolation of the polymer through coagulation of the polymer dispersion, either mechanically, at high shear speed, or chemically, by adding strong mineral acids such as HCl or HNO3. The coagulated fluorothermoplastics are usually agglomerated by adding organic solvents that are usually not water-miscible, such as benzene or fluorinated hydrocarbons. The isolated polymer resins are washed with water. With 5 to 10 tons of water used for each ton of resin, relatively large amounts of process water, called aqueous effluent here, are generated. The aqueous effluent contains an average of 30 to 1000 ppm of PFOS. It is characteristic of the coagulation of fluoropolymers produced in the presence of fluorinated emulsifiers, that the emulsifier is desorbed to a great extent during coagulation, and a very large proportion of it is washed out. Thus, more than 80% of the fluorinated emulsifiers that are used get into the aqueous effluent. Along with latex particles, this aqueous effluent also contains the additives from the various polymerization formulas, such as buffers, initiators and various chain transmitters, for example, diethyl malonic ester and its decomposition products, alkyl chloride or alkane, benzene and other organic compounds from the processing.
The fluorinated emulsifier, APFOS in particular, is a very expensive compound and contributes very substantially to the overall cost of fluoropolymers from emulsion polymerization. As a result, its recovery is very important for economic reasons. In addition, fluorinated emulsifiers are practically non-degradable biologically, and injury to the health is suspected according to the most recent studies.
It is therefore desirable to remove the emulsifier from the aqueous effluent, to recover it and to recycle it to the emulsion polymerization. Removal from the aqueous effluent is preferably carried out using anion exchanger resins in accordance with U.S. Pat. No. 3,882,153 and EP-B-14 431. Other aqueous effluent treatments were suggested in this regard in WO-A-99/62858 and WO-A-99/62830. Both aqueous effluent treatments pertain to removal of PFOS from industrial aqueous effluents by means of anion exchangers, whereby strongly basic anion exchangers are recommended. The anionic exchange is hindered by the presence of fluoropolymer latex particles that clog the anion exchanger columns. According to WO-A-99/62858, the latex particles are precipitated through the addition of relatively large amounts of salt before the ionic exchange.
According to WO-A-99/62830, the fine latex particles are stabilized through the addition of nonionic tensides, thus preventing clogging of the anion exchanger columns, even during continuous operation.
Removal of the emulsifier from the aqueous effluent with an anion exchanger resin is very efficient. Particularly in the case of strongly basic anion exchanger resins, practically quantitative removal takes place. The emulsifier is selectively adsorbed, and thus the entire capacity of the ionic exchanger can be fully utilized.
However, the elution, termed recovery in the following, is made substantially more difficult in accordance with the strong adsorption. For example, the elution with solutions of 1 mol/liter each of NH3, NaOH and KF of a strongly basic anion exchanger resin that is charged to breakdown with APFOS yields APFOS concentrations in the range of only 0.1 mmol/liter (40 ppm) in the eluate. Consequently, this method for recovering APFOS from larger volumes of aqueous effluent is not economically justifiable.
To elute for economically viable recirculation, an eluate peak concentration that is as high as possible is needed. According to EP-B-14 431, a peak concentration of 180,000 ppm with an eluent comprised of 89 wt.-% methanol, 4 wt.-% sulfuric acid and 7 wt.-% water can be achieved. The elution takes place in an acidic environment.
In a basic environment, according to U.S. Pat. No. 3,882,153 a relatively high peak concentration is achieved with an APFOS-charged, weakly basic anion exchanger during elution with 0.5 to 2 molar aqueous ammonia solution. However, the peak concentration of APFOS that can be achieved is smaller than in EP-B-14 431 by a factor of 2 to 3, and is still not satisfactory for a technically practicable process.
According to the unpublished German patent application 199 32 771.8 of Jul. 14, 1999, the elution of strongly basic anion exchanger resins in a basic environment runs substantially more efficiently in the presence of organic, water-miscible solvents. However, the peak concentration of 180,000 of EP-B-14 431 is achieved only with mixtures that are relatively laborious technically.
The object of the present invention is to make available a method in which fluorinated emulsifiers, PFOS in particular, can be recovered from anion exchanges with technically simple eluent mixtures with APFOS concentrations that are as high as possible.
It has now been found that with moderately and weakly basic anion exchanger resins, the PFOS concentrations in the eluate can be substantially increased with ammoniacal organic solvents. This eluate concentration is increased even further in the presence of alkali hydroxides.
The solution is a method for eluting fluorinated emulsifiers is made available in which weakly to moderately strong basic anion exchanger resins that are charged with fluorinated emulsifiers, particularly PFOS, are eluted with ammonia containing, water-miscible organic solvents.
According to the invention, the 180,000 ppm that can be achieved in the state of the art can be markedly surpassed, to beyond 300,000 ppm, for example, and specifically by using technically simple eluent mixtures.
The present invention makes possible significantly higher peak concentrations, thus considerably reducing the amount of highly flammable organic solvent needed for regenerating an anion exchanger resin.
Concentrated eluates of this type bring with them substantial advantages for the technical handling of the recovery. In addition, the recycling of PFOS becomes significantly easier, as will be explained in the following. The organic solvent, including the ammonia, is separated by means of distillation and is replaced with water as required. The distillate mixture can be used for regenerating the ion exchanger directly. During distillation, the organic impurities from the aqueous effluent from the processing, such as chain transmitters or benzene, are removed from the eluate in a trouble-free manner during removal of the organic solvents, because the salts of PFOS are not volatile in water vapor.
The present invention represents a technical method for recovering PFOS from industrial aqueous effluents. Recycling in the sense of the present invention consists in making available the emulsifier, which is free of the impurities that enter during polymerization.
The ammonia concentration in the mixture is advantageously a minimum of 0.1 mol/liter and a maximum of 4 mol/liter, preferably 1 to 2.5 mol/liter. The ammonia concentration is advantageously produced by adding appropriate amounts of concentrated aqueous ammonia solutions, such as are commercially available, to the organic solvent. The system must contain an adequate amount of water so that the required anions can be released.
Suitable organic solvents are water-miscible, and should have a boiling point below 150xc2x0 C., preferably below 110xc2x0 C. xe2x80x9cMisciblexe2x80x9d is preferably to be understood in the sense of xe2x80x9cinfinitely misciblexe2x80x9d. Preferred solvents, which can be used individually or in a mixture, are alkanols with 1 to 4 carbon atoms, acetone, dialkyl ethers of monoglycol and diglycol, whereby alkyl groups are understood to mean methyl or ethyl. Especially preferred solvents are methanol, ethanol, n- and iso-propanol and dimethyl monoglycol ether. The essential cation is the ammonia ion. Addition of alkali hydroxides leads to higher eluate concentrations.
The definition of strongly, moderately and weakly basic anion exchangers can be found in the xe2x80x9cEncyclopedia of Polymer Science and Engineeringxe2x80x9d, John Wiley and Sons, 1985, Volume 8, page 347, and xe2x80x9cKirk-Othmerxe2x80x9d, John Wiley and Sons, 3rd Edition, Volume 13, page 687. Strongly basic anion exchangers typically contain quaternary amines, moderate strength tertiary amines and the weak secondary amines as functional exchange locations. The resin vendors classify the strength of the resins in the product description supplements.
Moderate strength anion exchangers are preferred because of their good effectiveness in removing APFOS from industrial aqueous effluents, especially in the presence of the nonionic emulsifiers described in German patent application 199 33 696.2 of Jul. 17, 1999.
In principle, this inventive method can be carried out with all fluorinated anionic emulsifiers. Essentially, this involves fluorinated alkanoic carboxylic and alkanoic sulfonic acids, whereby the alkyl residue is partly or preferably completely fluorinated and is generally linear or even branched.
Primarily to be understood here by the term fluorinated emulsifiers are perfluorinated alkanoic acids with the formula CF3(CF2)nCOOH (n=3 to 10), in particular PFOS, on which the method according to the invention can preferably be applied. Also covered by this term, however, are partially fluorinated alkanoic acids with the formula XCF2(CF2)nCOOH (Xxe2x95x90H or Cl, n=3 to 10), perfluorinated or partially fluorinated alkanoic sulfonic acids with the formula XCF2(CF2)nSO3H (Xxe2x95x90H or preferably F, n=3 to 10), and perfluoro-[(xcex2-propoxy)propionic acids]. The fluorinated emulsifier can also contain [(CF2)nO] groups where nxe2x89xa72. These fluorinated emulsifier acids can also be eluted according to the method per the invention. Mixtures of the named fluorinated emulsifier acids can also be adsorbed and eluted, particularly those that contain PFOS as a primary constituent.

Method for recovering fluorinated emulsifiers