The present invention relates to a process for the reaction of at least one organic compound with one oxygen-delivering substance, for example a hydroperoxide, in the presence of at least one catalyst containing a metal-organic framework material comprising pores and a metal ion and an at least bidentate organic compound, said bidentate organic compound being coordinately bound to the metal ion. Further, the present invention is directed to the products being obtainable by the process according to the invention.

The present invention relates to a process for the epoxidation of at least one organic compound with oxygen or an oxygen-delivering compound, in the presence of at least one catalyst containing a metal-organic framework material comprising pores and a metal ion and an at least bidentate organic compound, said bidentate organic compound being coordinately bound to the metal ion. Further, the present invention is directed to the products being obtainable by the process according to the invention.
Reactions of organic compounds with oxidizing agents as hydroperoxides are well known in the prior art, for example from DE 100 55 652.3 and further patent applications of the present applicant, such as DE 100 32 885.7, DE 100 32 884.9 or DE 100 15 246.5.
The state of the art for catalysts used in epoxidation reactions is given by materials containing zeolites, in particular catalysts which comprise a titanium-, vanadium-, chromium-, niobium- or zirconium-containing zeolite as a porous oxidic material. Such catalysts are described, for example, in WO 00/07965.
In a promising novel and alternative strategy to create micro- and/or mesoporous catalytically active materials, metal ions and molecular organic building blocks are used to form so-called metal-organic frameworks (MOFs). The metal-organic framework materials as such are described, for example, in. U.S. Pat. No. 5,648,508, EP-A-0 709 253, M. O""Keeffe et al., J. Sol. State Chem., 152 (2000) p. 3-20, H. Li et al., Nature 402 (1999) p. 276 seq., M. Eddaoudi et al., Topics in Catalysis 9 (1999) p. 105-111,B. Chen et al., Science 291 (2001) p. 1021-23. Among the advantages of these novel materials, in particular for applications in catalysis, are the following:
(i) larger pore sizes can be realized than for the zeolites used presently
(ii) the internal surface area is larger than for porous materials used presently
(iii) pore size and/or channel structure can be tailored over a large range
(iv) the organic framework components forming the internal surface can be functionalized easily.
However, these novel porous materials have only been described as such. The use of these catalytically active materials in reactions of technical importance, in particular for epoxidation reactions, has not been disclosed yet.
It is an object of the present invention to provide a catalyst for the reaction of organic compounds with oxygen and/or oxygen-delivering compounds, wherein the catalyst for said reaction contains a novel material, in addition to, or instead of, catalytic materials according to the prior art, particularly in addition to, or instead of, zeolites.
This object is solved by providing a process for the epoxidation of at least one organic compound with oxygen and/or at least one oxygen-delivering compound in the presence of a catalyst, wherein said catalyst contains a metal-organic framework material comprising pores and at least one metal ion and at least one at least bidentate organic compound, which is coordinately bound to said metal ion.
As epoxidation agents, oxygen and oxygen-delivering compounds can be used. This includes but is not limited to ozone, water, oxidizing enzymes, reactive oxides, such as permanganates, chromic oxide, nitric oxide and the like. If oxygen is used, the gas may be mixed with other reactive gases and/or inert gases. Preferred are hydroperoxides known from the prior art which are suitable for the reaction of the organic compound. Mixtures of at least two of the aforementioned epoxidation agents are included as well. The generic formula of a hydroperoxide can be given as Rxe2x80x94Oxe2x80x94Oxe2x80x94H. In principle, any organic or inorganic entity known to the expert in the field may be used as the group xe2x80x9cRxe2x80x9d. Examples of such hydroperoxides are tertbutyl hydroperoxide, ethylbenzene hydroperoxide, and cumenehydroperoxide. In the present invention, preference is given to using hydrogen peroxide as hydrol peroxide. The present invention therefore also provides a process as described above, in which the hydroperoxide used is hydrogen peroxide. Preference is given to using an aqueous hydrogen peroxide solution. The hydrogen peroxide, or any hydroperoxide for that matter, can be either prepared outside the reaction or by starting from hydrogen and oxygen, or other suitable components, in situ within the reaction.
With respect to epoxidation reactions, DE 100 55 652.3, DE 100 32 885.7, DE 100 32 884.9, DE 100 15 246.5, DE 199 36 547.4, DE 199 26 725.1, DE 198 47 629.9, DE 198 35 907.1, DE 197 23 950.1 are fully encompassed within the content of the present application with respect to their respective content.
Other known processes for epoxidation reactions are not excluded from the present application, and are, for example, described in Weissermel, Arpe xe2x80x9cIndustrielle Organische Chemiexe2x80x9d, publisher VCH, Weinheim, 4th Ed., pages 288 to 318 and in U. Onken, Anton Behr, xe2x80x9cChemische Prozesskundexe2x80x9d, Vol. 3, Thieme, 1996, pages 303 to 305 as well as Weissernel, Arpe xe2x80x9cIndustrial Organic Chemistryxe2x80x9d, 5th Ed., Wiley, 1998, pages 159 to 181.
Among the reactions which are possible in the process of the present invention, the following are mentioned by way of example and without limiting the general scope of the present invention:
the epoxidation of olefins, e.g. the preparation of propylene oxide from propylene and H2O2 or from propylene and mixtures which provide H2O2 in situ;
hydroxylations such as the hydroxylation of monocyclic, bicyclic or polycyclic aromatics to give monosubstituted, disubstituted or higher-substituted hydroxyaromatics, for example the reaction of phenol and H2O2, or of phenol and mixtures which provide H2O2 in situ, to form hydroquinone;
oxime formation from ketones in the presence of H2O2, or mixtures which provide H2O2 in situ, and ammonia (ammonoximation), for example the preparation of cyclohexanone oxime from cyclohexanone;
the Baeyer-Villiger oxidation.
In the process of the present invention, organic compounds which have at least one Cxe2x80x94C double bond are epoxidized.
Examples of such organic compounds having at least one Cxe2x80x94C double bond are the following alkenes: ethene, propene, 1-butene, 2-butene, isobutene, butadiene, pentene, piperylene, hexenes, hexadienes, heptenes, octenes, diisobutene, trimethylpentene, nonenes, dodecene, tridecene, tetradecene to eicosene, tripropene and tetrapropene, polybutadienes, polyisobutenes, isoprenes, terpenes, geraniol, linalool, linalyl acetate, methylenecyclopropane, cyclopentene, cyclohexene, norbornene, cycloheptene, vinylcyclohexane, vinyloxiran, vinylcyclohexene, styrene, cyclooctene, cyclooctadiene, vinylnorbornene, indene, tetrahydroindene, methylstyrene, dicyclopentadiene, dinvinylbenzene, cyclododecene, cyclododecatriene, stilbene, diphenylbutadiene, vitamin A, beta-carotene, vinylidene fluoride, allyl halides, crotyl chloride, methallyl chloride, dichlorobutene, allyl alcohol, methallyl alcohol, butenols, butenediols, cyclopentenediols, pentenols, octadienols, tridecenols, unsaturated steroids, ethoxyethene, isoeugenol, anethole, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, vinylacetic acid, unsaturated fatty acids such as oleic acid, linoleic acid, palmitic acid, naturally occurring fats and oils.
The process of the present invention is preferably carried out using alkenes having from 2 to 8 carbon atoms. Particular preference is given to reacting ethene, propylene and butene.
As has been mentioned above, metal-organic framework materials as such are described in, for example, U.S. Pat. No. 5,648,508, EP-A-0 709 253, M. O""Keeffe et al., J Sol. State Chem., 152 (2000) p. 3-20, H. Li et al., Nature 402 (1999) p. 276 seq., M. Eddaoudi et al., Topics in Catalysis 9 (1999) p. 105-111, B. Chen et al., Science 291 (2001) p. 1021-23. An inexpensive way for the preparation of said materials is the subject of DE 10111230.0. The content of these publications, to which reference is made herein, is fully incorporated in the content of the present application.
The catalyst used in the present invention contains at least one of the metal-organic framework material, for example one of the materials described below.
The metal-organic framework materials, as used in the present invention, comprise pores, particularly micro- and/or mesopores. Micropores are defined as being pores having a diameter of 2 nm or below and mesopores as being pores having a diameter in the range of above 2 nm to 50 nm, respectively, according to the definition given in Pure Applied Chem. 45, p. 71 seq., particularly on p. 79 (1976). The presence of the micro- and/or mesopores can be monitored by sorption measurements for determining the capacity of the metal-organic framework materials to take up nitrogen at 77 K according to DIN 66131 and/or DIN 66134.
For example, a type-I-form of the isothermal curve indicates the presence of micropores [see, for example, paragraph 4 of M. Eddaoudi et al., Topics in Catalysis 9 (1999)]. In a preferred embodiment, the specific surface area, as calculated according to the Langmuir model (DIN 66131, 66134) preferably is above 5 m2/g, further preferred above 10 m2/g, more preferably above 50 m2/g, particularly preferred above 500 m2/g and may increase into the region of to above 3000 m2/g.
As to the metal component within the framework material that is to be used according to the present invention, particularly to be mentioned are the metal ions of the main group elements and of the subgroup elements of the periodic system of the elements, namely of the groups Ia, Ia, IIIa, IVa to VIIIa and Ib to VIb. Among those metal components, particular reference is made to Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb, and Bi, more preferably to Zn, Cu, Ni, Pd, Pt, Ru, Rh and Co. As to the metal ions of these elements, particular reference is made to: Mg2+, Ca2+, Sr2+, Ba2+, Sc3+, Y3+, Ti4+, Zr4+, Hf4+, V4+, V3+, V2+, Nb3+, Ta3+, Cr3+, Mo3+, W3+, Mn3+, Mn2+, Re3+, Re2+, Fe3+, Fe2+, Ru3+, Ru2+, Os3+, Os2+, Co3+, Co2+, Rh2+, Rh+, Ir2+, Ir+, Ni2+, Ni+, Pd2+, Pd+, Pt2+, Pt+, Cu2+, Cu+, Ag+, Au+, Zn2+, Cd2+, Hg2+, Al3+, Ga3+, In3+, Tl3+, Si4+, Si2+, Ge4+, Ge2+, Sn4+, Sn2+, Pb4+, Pb2+, As5+, As3+, As+, Sb5+, Sb3+, Sb+, Bi5+, Bi3+ and Bi+.
With regard to the preferred metal ions and further details regarding the same, particular reference is made to: EP-A 0 790 253, particularly to p. 10, 1. 8-30, section xe2x80x9cThe Metal Ionsxe2x80x9d, which section is incorporated herein by reference.
In addition to the metal salts disclosed in EP-A 0 790 253 and U.S. Pat. No. 5,648,508, other metallic compounds can be used, such as sulfates, phosphates and other complex counter-ion metal salts of the main- and subgroup metals of the periodic system of the elements. Metal oxides, mixed oxides and mixtures of metal oxides and/or mixed oxides with or without a defined stoichiometry are preferred. All of the above mentioned metal compounds can be soluble or insoluble and they may be used as starting material either in form of a powder or as a shaped body or as any combination thereof.
As to the at least bidentate organic compound, which is capable to coordinate with the metal ion, in principle all compounds can be used which are suitable for this purpose and which fulfill the above requirements of being at least bidentate. Said organic compound must have at least two centers, which are capable to coordinate with the metal ions of a metal salt, particularly with the metals of the aforementioned groups. With regard to the at least bidentate organic compound, specific mention is to be made of compounds having
i) an alkyl group substructure, having from 1 to 10 carbon atoms,
ii) an aryl group substructure, having from 1 to 5 phenyl rings,
iii) an alkyl or aryl amine substructure, consisting of alkyl groups having from 1 to 10 carbon atoms or aryl groups having from 1 to 5 phenyl rings,
said substructures having bound thereto at least one at least bidentate functional group xe2x80x9cXxe2x80x9d, which is covalently bound to the substructure of said compound, and wherein X is selected from the group consisting of
CO2H, CS2H, NO2, SO3H, Si(OH)3, Ge(OH)3, Sn(OH)3, Si(SH)4, Ge(SH)4, Sn(SH)3, PO3H, AsO3H, AsO4H, P(SH)3, As(SH)3, CH(RSH)2, C(RSH)3, CH(RNH2)2, C(RNH2)3, CH(ROH)2, C(ROH)3, CH(RCN)2, C(RCN)3, wherein R is an alkyl group having from 1 to 5 carbon atoms, or an aryl group consisting of 1 to 2 phenyl rings, and CH(SH)2, C(SH)3, CH(NH2)2, C(NH2)2, CH(OH)2, C(OH)3, CH(CN)2 and C(CN)3.
Particularly to be mentioned are substituted or unsubstituted, mono- or polynuclear aromatic di-, tri- and tetracarboxylic acids and substituted or unsubstituted, aromatic, at least one hetero atom comprising aromatic di-, tri- and tetracarboxylic acids, which have one or more nuclei.
A preferred ligand is 1,3,5-benzene tricarboxylate (BCT). Further preferred ligands are ADC (acetylene dicarboxylate), NDC (naphtalen dicarboxylate), BDC (benzene dicarboxylate), ATC (adamantane tetracarboxylate), BTC (benzene tri-carboxylate), BTB (benzene tribenzoate), MTB (methane tetrabenzoate) and ATB (adamantane tribenzoate).
Besides the at least bidentate organic compound, the framework material as used in accordance with the present invention may also comprise one or more mono-dentate ligand(s), which is/are preferably selected from the following mono-dentate substances and/or derivatives thereof:
a. alkyl amines and their corresponding alkyl ammonium salts, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms (and their corresponding ammonium salts);
b. aryl amines and their corresponding aryl ammonium salts having from 1 to 5 phenyl rings;
c. alkyl phosphonium salts, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms;
d. aryl phosphonium salts, having from 1 to 5 phenyl rings;
e. alkyl organic acids and the corresponding alkyl organic anions (and salts) containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms;
f. aryl organic acids and their corresponding aryl organic anions and salts, having from 1 to 5 phenyl rings;
g. aliphatic alcohols, containing linear, branched, or cyclic aliphatic groups, having from 1 to 20 carbon atoms;
h. aryl alcohols having from 1 to 5 phenyl rings;
i. inorganic anions from the group consisting of: sulfate, nitrate, nitrite, sulfite, bisulfite, phosphate, hydrogen phosphate, dihydrogen phosphate, diphosphate, triphosphate, phosphite, chloride, chlorate, bromide, bromate, iodide, iodate, carbonate, bicarbonate, and the corresponding acids and salts of the aforementioned inorganic anions,
j. ammonia, carbon dioxide, methane, oxygen, ethylene, hexane, benzene, toluene, xylene, chlorobenzene, nitrobenzene, naphthalene, thiophene, pyridine, acetone, 1-2-dichloroethane, methylenechloride, tetrahydrofuran, ethanolamine, triethylamine and trifluoromethylsulfonic acid.
Further details regarding the at least bidentate organic compounds and the mono-dentate substances, from which the ligands of the framework material as used in the present application are derived, can be taken from EP-A 0 790 253, whose respective content is incorporated into the present application by reference.
Within the present application, framework materials of the kind described herein, which comprise Zn2+ as a metal ion and ligands derived from terephthalic acid as the bidentate compound, are particularly preferred. Said framework materials are known as MOF-5 in the literature.
Further metal ions and at least bidentate organic compounds and mono-dentate substances, which are respectively useful for the preparation of the framework materials used in the present invention as well as processes for their preparation are particularly disclosed in EP-A 0 790 253, U.S. Pat. No. 5,648,508 and DE 10111230.0.
As solvents, which are particularly useful for the preparation of MOF-5, in addition to the solvents disclosed in the above-referenced literature, dimethyl formamide, diethyl formamide and N-methylpyrollidone, alone, in combination with each other or in combination with other solvents may be used. Within the preparation of the framework materials, particularly within the preparation of MOF-5, the solvents and mother liquors are recycled after crystallization in order to save costs and materials.
The pore sizes of the metal-organic framework can be adjusted by selecting suitable organic ligands and/or bidendate compounds (=linkers). Generally, the larger the linker, the larger the pore size. Any pore size that is still supported by a the metal-organic framework in the absence of a host and at temperatures of at least 200xc2x0 C. is conceivable. Pore sizes ranging from 0,2 nm to 30 nm are preferred, with pore sizes ranging from 0,3 nm to 3 nm being particularly preferred.
In the following, examples of metal-organic framework materials (MOFs) are given to illustrate the general concept given above. These specific examples, however, are not meant to limit the generality and scope of the present application.
By way of example, a list of metal-organic framework materials already synthesized and characterized is given below. This also includes novel isoreticular metal organic framework materials (IR-MOFs), which may be used in the context of the present application. Such materials having the same framework topology while displaying different pore sizes and crystal densities are described, for example in M. Eddouadi et al., Science 295 (2002) 469, whose respective content is incorporated into the present application by reference
The solvents used are of particular importance for the synthesis of these materials and are therefore mentioned in the table. The values for the cell parameters (angles xcex1, xcex2 and xcex3 as well as the spacings a, b and c, given in Angstrom) have been obtained by x-ray diffraction and represent the space group given in the table as well.
Examples for the synthesis of these materials as such can, for example, be found in: J. Am. Chem. Soc. 123 (2001) pages 8241ff or in Acc. Chem. Res. 31 (1998) pages 474ff, which are fully encompassed within the content of the present application with respect to their respective content.
The separation of the framework materials, particularly of MOF-5, from the mother liquor of the crystallization may be achieved by procedures known in the art such as solid-liquid separations, centrifugation, extraction, filtration, membrane filtration, cross-flow filtration, flocculation using flocculation adjuvants (non-ionic, cationic and anionic adjuvants) or by the addition of pH shifting additives such as salts, acids or bases, by flotation, as well as by evaporation of the mother liquor at elevated temperature and/or in vacuo and concentrating of the solid. The material obtained in this step is typically a fine powder and cannot be used for most practical applications, e.g. in catalysis, where shaped bodies are required.

Process for the epoxidation of an organic compound with oxygen or an oxygen-delivering compounds using catalysts containing metal-organic frame-work materials

The Regents of the University of Michigan


Lithographic printing ink formulations compatible with cationic catalysts containing a diluent and rheology modifying resins curable by cationic polymerization in the presence of water or fountain solution.

This invention relates to novel lithographic printing ink compositions having low amounts of volatile organic components (VOC) that consist of diluents polymerizable by cationic addition polymerization and cured in the presence of water or fountain solution.
Today, a major goal of national environmental programs is the reduction or elimination of evaporative emissions of organic chemicals into the atmosphere which would eliminate: the health risks associated with continual human exposure to organic vapors in the work-place; the potential contribution of VOC to hydrocarbon and ozone-related pollution of the atmosphere; and the theoretical contribution VOC may make to the atmospheric xe2x80x9cgreenhouse effectxe2x80x9d. Manufacturers across the industrial spectrum have been called upon to look at the formulations of their end products and manufacturing processes and change or alter the product formulations or process steps consistent with the national goal. This is a prodigious challenge, one not easily met in the best of circumstances and not achievable without a severe deleterious impact on end-product properties and/or process cost.
Inks typically include a variety of organic components in their formulation such as one or more organic solvents, monomers, oligomers, crosslinking agents, gelling agents and the like, all selected for their contribution to application-specific ink properties. For lithographic printing inks, conventional web offset heatset inks (WOHS) comprise the largest market segment and are, consequently, a most important segment to convert to VOC-free systems. These inks usually contain a pigment, polymeric binders, additives such as driers or talcs, and volatile solvents or diluents. As their name implies, the inks dry by a setting mechanism. The drying takes place by removal of the solvent when the printed article passes through a high temperature oven where solvent is evaporated into the atmosphere. As such, the drying process for these inks presents a significant opportunity for the printing industry to reduce VOC pollutants emanating from their current printing practices. But that opportunity must be captured without severely affecting the physical printing operation and its cost.
WOHS inks have been formulated that eliminate or substantially reduce VOCs by replacing solvents or diluents in the formulation with acrylate monomers and acrylated oligomers which serve as diluents for pigments, etc. These inks are then cured by free radical initiated polymerization to form polymeric binders. In this instance, as a first choice the formulation is restricted to monomers that polymerize by well recognized free radical initiation mechanisms, where the rate of polymerization is fast and commensurate with the web print speeds of WOHS. When this requirement is is factored into the end properties required of the ink polymeric binder, the choice of monomer is largely restricted to acrylates and the acrylate moiety. But acrylate monomers are relatively expensive for products of this class. Therefore, when coupled with the additional cost pressures inherent in product reformulation, the use of acrylates to reduce VOC produces a severe upward pressure on the cost of WOHS inks.
It is well known in polymer science that there are other means to catalyzing monomers that yield polymers with physical properties potentially useful in low VOC WOHS inks. These monomers polymerize at rates competitive with those achieved by the free radical polymerization of acrylates and, hence, they are compatible with the speed of WOHS printing. These alternative methods include anionic and cationic catalysis, redox initiation, thermal and electron beam. However, each of these approaches have strengths and weaknesses when considered as a basis for reformulating WOHS inks for lower VOC content. Electron Beam initiated polymerization would, for example, require modifications to the physical printing plant to accommodate new equipment at a potentially steep cost. Tonically catalyzed polymerization would present a challenge to the practical feasibility of the overall offset printing process that takes place in the presence of aqueous fountain solutions.
Fountain solutions are typically an aqueous mixture of chemical components used in off-set printing to keep the non-image area of the lithographic printing plate free of ink and often contain basic components to produce high pH, acidic components for low pH or acid/base buffers designed to maintain an intermediate fountain solution pH of about 3, or at least 5-7. Consequently, one skilled in the art would reasonably expect that fountain solutions to seriously retard or stop inks catalyzed by cationic catalysts from curing.
McKie et al, GB2142279A, describes an energy curable printing ink composition consisting of a cationic polymerizable resin, diluent, photoinitiator, and colorant. However, the printing is a screen ink and screen inks typically have a viscosity between 15 and 60 poises. By contrast, UV curable lithographic inks have a viscosity above 100 poises (R. H. Leach, xe2x80x9cThe Printing Ink Manualxe2x80x9d, Fourth Edition, 312 and 498 (1988)). Moreover, screen inks are used in dry transfer printing processes and therefore are not curable in the presence of water or fountain solution.
In general, it is known that water, particularly in the form of high humidity or moisture, poisons anionic and cationic polymerizations. So it would seem unlikely, that any cationically catalyzed ink curing would work in the presence of water or fountain solution; see UV Curing: Science and Technology, Vol. II Chapter 6, pgs. 248-282, by S. Peter Pappas, Published by Marketing Technology Corp. Thus, high quality, commercial grade, UV curable lithographic printing ink formulations, polymerizable by cationic addition polymerization and essentially devoid of VOCs and acrylates are desirable.
The object of the present invention is to develop a lithographic printing ink formulation having a low complement of VOC yet fully compatible with commercial printing operations.
It is also an objective of the present invention to formulate low VOC lithographic UV curable printing inks that are cured in the presence of water or fountain solution.
Another object of the invention is to formulate a WOHS ink employing a cationic catalyst and gelling agents compatible with cationic UV cured systems.
A lithographic printing ink cured by UV radiation in the presence of water or fountain solution comprising: a diluent polymerizable by cationic addition polymerization; a cationic photoinitiator; rheology modifying resin binder and colorant; having a viscosity greater than 100 poises.
The images produced by the novel printing ink formulations of the invention are cured following offset printing by a novel process comprising a surprisingly effective cationic catalytic polymerization of the reactive monomer diluents or derivatized oligomers in the formulation. A binder for the ink system is formed that provides a hard coat and a high gloss printed image. Despite the presence of aqueous fountain solution in proximal contact with the formed image subsequent to printing, it has been found that the cationic polymerization of reactive monomers in the uncured ink image is, nevertheless, readily initiated and effectively cures the printed image.
The cationic polymerization catalyst photoinitiators included in the ink formulations of the invention are cationic catalyst precursors that have the capability of releasing cationic catalysts when acted upon by an appropriate agent. Preferably, the initiators release cationic catalyst upon exposure to an energy source such as heat, light or an electron beam. A useful initiator is one which reacts or rearranges upon exposure to ultraviolet (UV) light to release a cationic catalyst which goes unaffected by fountain solution. A particularly preferred cationic precursor is Cyracure 6990, available from Union Carbide. Upon exposure to UV light and subsequent to printing, Cyracure 6990 releases a super acid, which catalyzes the polymerization of the reactive monomers to form a cured printed image. Heat may also be applied to the printed article during or after the curing step to facilitate or complete curing.
While the instant discovery obviates the need to formulate free radical polymerized inks systems for low VOC, a need for rheology modifiers compatible with these cationic systems was formed. This need however, has been met by the discovery of a useful class of high molecular weight rosin esters that form gel like structures compatible in cationically polymerizable diluents. When these rosin esters are used in the present invention which contains cationically polymerizable diluents, a novel lithographic printing ink or over print coating varnish results wherein the rheology of the ink or varnish is controllable and the cured print image is a hard and glossy and has good adhesion.
Optionally, a non-ink protective top coating for printing can be produced by the invention by eliminating the pigment from the formulation. The composition, so formed, can be advantageously used in off-set printing to form a clear, protective top coating over the cured inked image immediately and subsequent to the printing and image curing sequence of the printing process. The top coating may use similar diluents and catalyst precursors as those employed in the ink and can be cured with a similar UV light source.
The WOHS printing inks of the invention meet the print quality and environmental requirements of having a low or negligible VOC content by using low cost, resin-producing, film forming, monomers as diluents that provide a cost advantage over more conventional low VOC containing acrylates. By resorting to a means other than free radical polymerization, relatively inexpensive monomers can now be used in conjunction with catalyst systems producing inks having cure rates that are fully compatible with WOHS printing speeds. The catalyst initiator systems used in the invention are unique as that they are present as catalyst precursors, preferably cationic photoinitiators, yet they are activated in the curing step of the printing process.
In the present invention, the curing of ink can be carried out with a wide range of monomers or oligomers by means such as thermal initiation, electron beam initiation, or UV initiation. For practical reasons though, ionically catalyzed curing is preferred since the polymerization rates are fast and commensurate with WOHS printing speeds. In addition, the cure step does not require major additions or modifications of the printing apparatus. Also, cationic polymerization proceeds nearly to completion, leaving little or no residue of monomer that may contribute to elevated VOCs. Of the available cure means for the printed ink image, it has been discovered that cationic catalysis works well in the presence of fountain solutions and the resulting properties of the cured ink are excellent.
Diluents
The diluents used in the ink compositions of the invention provide a two-fold function. They are used to replace organic solvents ordinarily used in ink formulations to solubilize the components of the ink. They are also included to polymerize and/or copolymerize (subsequent to printing) the film and binder of the printed ink image. The diluents may be low molecular weight liquid monomers and comonomers including oligomers that contain cationically crosslinkable moieties.
For cationically polymerizable diluent monomers or comonomers, a wide variety of ethylenically unsaturated monomers, oxiranes, oxetanes and oxolanes can be used. Vinyl compounds are an especially useful resource of ethylenically unsaturated compounds for diluent monomers. Although many vinyl monomers are not readily polymerized by cationic polymerization, useful vinyl monomers which may be homopolymerized or copolymerized include alkyl vinyl ethers such as methyl vinyl ether, styrene, alpha alkyl styrene and isobutylene and other alpha olefins.
One preferred diluent is divinyl ether of triethylene glycol.
It is well known that the epoxide group, oxirane, can be readily polymerized by cationic polymerization; consequently, oxirane and substituted oxiranes are a preferred resource to provide diluent monomers useful in the present invention. These oxiranes include oxides of alkenes, alkadienes, cycloalkenes, cycloalkadienes, and oxides of olefinically unsaturated natural products such vegetable oils and natural resins including soya oil, linseed oil, unsaturated fats, unsaturated hydrocarbons, used alone or in combination. Specific examples include vinylcyclohexene dioxide (available from Union Carbide), 1,2,7,8-diepoxyoctane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (available from Ciba-Geigy), Bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate (available from Union Carbide), Bis(3,4-epoxycyclohexylmethyl)adipate (available from Union Carbide), Butanediol diglycidyl ether, Cresyl glycidyl ether (available from Wilmington Chemical Corp.) and C12-C14 Alkyl glycidyl ether (available from Ciba-Geigy). Particularly useful oxiranes include limonene dioxide, oxides of linseed oil and oxides of soya oil, employed alone or in combination.
The oxiranes of the present invention have the following structure:
where R1, R2, R3 and R4 are independently selected from hydrogen, alkyl, alkenyl, aryl or cycloalken-diyl when R2 and R3 are taken in combination.
The reactive epoxy functionality of the diluents generally are in relatively low molecular weight monomers. However, it is within the scope of the present invention to include liquid oligomeric epoxidized monomers either alone or in combination with more typical low molecular weight epoxies. Variations such as this are conveniently made to augment the film properties or adhesion of the cured ink. These oligomers can have epoxidation functionality greater than two and may be cycloaliphatic or glycidyl type.
Those skilled in the art will appreciate that these diluents can be used individually or in combination as a mixture. Other co-diluents such as polyols can be used in the combination to enhance certain other properties of the ink such as homogeneity, cure speed or film flexibility.
Cationic Catalyst
The post-print curing of the ink compositions H is carried out by the cationic polymerization of monomeric diluents in contact with Lewis acids or Bronsted catalyst such as HF, H2SO4, AlCl3, BF3, FeCl3, TiCl4, CF3SO3H, ZnCl2 and P2O5. xe2x80x9cSuper acidsxe2x80x9d such as those prepared from mixed metal oxides and phosphorous or antimony fluorides can also be employed. Mixed metal oxide super acids are described by M. Hino and by K. Arata, J. Chem. Soc. Chem. Commun., 1987, pg. 1259; and in K. Arata and M. Hino, Proc. 9th International Congress on Catalysis, 1988, Vol. 4, pg. 1727 and U.S. Pat. No. 5,453,556. However, Lewis acid catalyst are not present in the inks as formulated since the preprinting stability, storability and overall utility of the inks would be compromised by any oligomer and/or high polymer formation. Rather, Lewis acid precursors are preferably used as cationic photoinitiators which, when acted upon, release Lewis acid catalysts, which in turn, initiate diluent polymerization and curing reactions. Such cationic catalyst precursors are defined herein as cationic polymerization catalyst initiators.
While the cationic catalyst is preferably included as a cationic photoinitiator in the ink formulation in another embodiment within the scope of the present invention the photoinitiator or an active cationic catalyst may be added as a portion of a two part ink formulation, i.e, one part containing the cationically curable components of the ink formulation and the other containing the cationic catalyst or photoinitiator. A suitable application means, for example, can combine the two parts at an appropriate moment on the lithographic plate to carry out the curing step of the printing process.
A preferred form of cationic polymerization catalyst initiators are photoinitiators which release active Lewis acid catalyst upon exposure to light, particularly UV light. Photoinitiators are well known in the field of catalysis chemistry and are available from Union Carbide Corporation; Ciba Specialties, Incorporated; Sartomer Corporation and General Electric Corporation. The preferred photoinitiators release super acids upon exposure to UV light according to the reaction:
where M is phosphorus or antimony and Ar is an aryl typically selected from a mixed triarylsulfonium, iodonium or ferrocenium salt. Irgacure 261 is a typical ferrocenium salt that releases a super acid catalyst when exposed to UV light. The super acid catalyzes the polymerization and crosslinking of, for example, epoxy groups in the printed ink image with themselves or with hydroxy groups.
UV light initiated cationic chemistry has many advantages over UV light initiated free radical chemistry for the preparation of low VOC inks. First, cationic polymerization is not inhibited by the presence of cationic and anionic polymerization reactions. As a result, the predictability of the success in curing WOHS lithographic inks with cationic catalysts was highly uncertain. Indeed, the course of the research confirmed that certain cationic photoinitiators known in the art, such as m, m1 dimethoxybenzyl tosylate, are moisture sensitive and are inadequate to perform as catalyst initiators for curing WOHS lithographic inks. However, certain cationic polymerization catalyst initiators reported herein were found to be sufficiently insensitive to fountain solution during printing and allowed curing to proceed successfully.
Without intending to be bound by theory, having made the instant discovery, it is now thought that the unexpected curing occurring in the presence of fountain solution is attributable to a combination of factors. First, the typical immiscibility of fountain solution with the inks, especially inks of the invention, forms a two phase emulsion that strongly inhibits the contamination of the ink phase by fountain solution components. Therefore, the concentration/activity of polymerization retarding components from the fountain solution to be found in the ink phase is small and the rate of any chain termination or catalyst poisoning reaction is consequently small. On the other hand, cationic addition polymerization reactions such as epoxy polymerization are known to proceed at high rates of reaction, even at room temperature. At the higher ink heat-set temperatures, typically used in the printing process, the reaction rates would be even higher. Accordingly, the competitive rates of reactions of chain termination/catalyst poisoning versus addition polymerization in the ink organic phase are overwhelmingly in favor of diluent addition polymerization unexpectedly and rapid ink curing occurs.
Photoinitiators
Particularly preferred photoinitiators employed in the ink formulations of the present invention are available from Union Carbide Corporation and are mixed triarylsulfonium hexafluoroantimonate salts (UVI-6974) and mixed triarylsulfonium hexafluorophosphate salts (UVI-6990) having the structures:
The photoinitiators are preferably used in quantities between 0.5 and 20 weight percent and more preferably in quantities between 5-10 weight percent and most preferably 6 weight percent.
Colorants
Colorants selected for UV cured cationic inks are limited due to the generation of a cationic catalyst that initiates the polymerization and crosslinking of the monomeric diluent groups. The presence of basic components in for example a pigment or a dye colorant, generally amines, can neutralize acid initiators and hinder the curing mechanism thereby reducing the curing speed to a point where printing is retarded. This creates a problem because many pigments are either treated with amines to promote dispersion or contain strong basic groups in their structure. However a wide range of special pigments have been found to be particularly useful in the inks of the present invention and can be employed without seriously reducing printing speeds. These colorants are available in a wide variety of colors and are compatible with UV cationic epoxide curing. Suppliers of dyes and pigments include BASF Corp., Harcros Corp., Sun Chemical Corp., Silberline Corp., U.S. Bronze Hoechst-Celanese Corp., Columbia Chemical Corp., Degussa Corp., Halox Corp. and DuPont Corp.
Rheology Modifying Resins
The key properties needed for the resin systems useful in the present invention are low cost, soluble in the diluent, particularly epoxy diluents, a reactive or non-reactive resin with a melting point of greater than 100xc2x0 C. and the ability to control the overall rheology of the printing ink.
To control the rheology of the inks of the invention it has been discovered that high molecular weight rosin ester resins can be used as rheology modifiers since these materials form gel type structures when dissolved in the diluents of the invention. Ordinarily, high molecular weight rosin ester resins are not used in acrylate-based low VOC inks because they are insoluble in the diluent system. However, they can dissolve in the low viscosity epoxies and vinyl ether that are the preferred diluents of the invention. Importantly, rosin ester resins do not interfere with the cationic polymerization curing of the inks. Preferred high molecular weight rosin ester resins are known in the art as self structured. These high molecular weight, self structured, rosin ester resins provide the following advantages to the inks of the invention: high elasticity and improved rheology; improved gloss and density due to good flow and emulsion stability on the lithographic press; cured film exhibits good adhesion on plastic, metal and metalized substrates due to low shrinkage; print quality is much better especially on high speed presses; cured ink exhibits good mechanical properties especially when is multifunctional epoxy diluents are used.
Rosin ester resins suitable for use in the present invention are well known in the art and are described, in part, in U.S. Pat. No. 5,498,684. They are prepared as derivatives of natural resins as described in Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 21, Fourth Edition, 1997, pgs. 291-301, incorporated herein by reference. High molecular weight rosin ester resins are preferred such as those obtained by esterification of abietic acid with pentaerythritol or Diels-Alder maleation of levopimaric acid with maleic anhydride and are available from Westvaco Corporation, Lawter Corporation, Union Camp Corporation and AKZO Corporation. Preferred rosin ester resins include Westvaco RP339, Lawter UR165 and DSM RL-62.
Reactive resins and modified resin systems customarily used in lithographic inks meeting these properties include polyester resins, phenolic resins, hydrocarbon resins, and the like bearing oxygen, vinyl ether or pendant hydroxy functionality.
The following resin systems are particularly suitable for use with the inks of the present invention:
Gelling Agents
A further method of controlling the rheology of the present ink formulation is to add gelling agents. Traditionally, these gelling agents are inorganic chelating agents that influence the degree and type of viscosity enhancement occurring in the ink. Although inorganic chelating agents are useful in low VOC ink formulations derived for acrylate oligomers and/or monomers, they are not all compatible with the cationic curing systems of the invention and may, in some instances create significant stability problems in the ink formulation. Therefore, gelling varnishes must be tailored for use in cationic systems.
Table 1 lists the weight percent range for each component in the ink of the present invention.
A particularly preferred magenta UV cationic lithographic ink composition is presented in Table 2.

Low VOC cationic curable lithographic printing inks


A catheter assembly for delivering an endoprosthesis within a body lumen. A delivery catheter assembly is provided which includes a stent with biocompatible material thereon for preventing the stent from expanding or otherwise dislodging from the catheter. The stent with biocompatible material is secured to an expandable member of a delivery catheter, whereby inflation of the expandable member causes the biocompatible material to fail, thereby permitting the stent to expand and deploy in a body lumen.

This invention relates to apparatus and methods for the treatment of body lumens, and particularly to delivery systems for endoprostheses. More particularly, the invention relates to biocompatible and/or bioabsorbable sheaths for self-expanding stents. The present invention also is directed to a delivery system for self-expanding stents which facilitates minimal stent movement during deployment to achieve more accurate stent placement within the patient""s vasculature.
Several interventional treatment modalities are presently used for heart disease including balloon and laser angioplasty, atherectomy and by-pass surgery. In a typical cardiovascular intervention, a guiding catheter having a preformed distal tip is percutaneously introduced over a first wire, such as a 0.035xe2x80x3 wire, that has been placed in the vasculature through a guiding sheath into an artery and advanced within the cardiovascular system until the distal tip of the guiding catheter is seated in the ostium of a coronary artery. The first wire is removed and a guidewire, such as a 0.014xe2x80x3 guidewire, is advanced distal to the treatment area. Then a dilatation catheter is back-loaded onto the guidewire and tracked to the treatment area through the guiding catheter. Once in position across the lesion, the balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressure (e.g., greater than four atmospheres) to compress the plaque of the lesion and to otherwise expand the inner lumen of the artery.
Further details of dilatation catheters, guidewires, and devices associated therewith for angioplasty procedures have been known for a number of years, and by way of example, several forms of such devices can be found in U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lindquist); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622 (Samson, et al.); U.S. Pat. No. 4,554,929 (Samson, et al.); U.S. Pat. No. 4,616,652 (Simpson); U.S. Pat. No. 4,638,805 (Powell); U.S. Pat. No. 4,748,982 (Horzewski, et al.); U.S. Pat. No. 5,507,768 (Lau, et al.); U.S. Pat. No. 5,514,154 (Lau, et al.); U.S. Pat. No. 5,451,233 (Yock); and U.S. Pat. No. 5,458,615 (Klemm, et al.); and U.S. Pat. No. 5,700,286 (Tartaglia, et al.).
A focus of recent development work in the treatment of heart disease has been directed to endoprosthetic devices called stents. Stents are generally cylindrically shaped intravascular devices which are placed within an artery to hold it open. The device can be used to reduce the likelihood of restenosis and to maintain the patency of a blood vessel immediately after intravascular treatments. In some circumstances, they can also be used as the primary treatment device where they are expanded to dilate a stenosis and then left in place.
Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of the balloon portion of a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent, which may be formed from shape-memory metals such as super-elastic nickel titanium (NiTi) alloys which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such self-expanding stents can typically be expanded without the need for application of a controlled force on the stent, such as is applied through the inflation of the balloon portion of a dilatation catheter. Such self-expanding stents may be manufactured from expandable heat-sensitive materials that allow for phase transformation of the materials to occur at set temperatures, resulting in the expansion and/or contraction of the stents.
One method and system developed for delivering stents to desired locations within the patient""s body lumen involves advancing the stent delivery system through the patient""s vascular system until the stent is positioned within the treatment area, and then inflating the expandable member on the catheter to expand the stent within the blood vessel. The expandable member is then deflated and the catheter withdrawn, leaving the expanded stent within the blood vessel, holding open the passageway thereof. This approach is common with stents of the first type, i.e., stents that are not self-expanding.
Implanting self-expanding stents within the patient""s vasculature often require different methods than the one set forth above for non-self-expanding stents. Some prior art stent delivery systems for self-expanding stents include a catheter with an inner lumen upon which the compressed or collapsed stent is mounted, and an outer restraining sheath which is eventually placed over the compressed stent prior to deployment. When the stent is to be deployed in the body vessel, the outer sheath is moved in relation to the inner lumen to xe2x80x9cuncoverxe2x80x9d the compressed stent, allowing the stent to move to its expanded condition. Some delivery systems utilize a xe2x80x9cpush-pullxe2x80x9d technique in which the outer sheath is retractable while the inner sheath is pushed forward or held in place. Still other systems use an actuating wire which is attached to the outer sheath. When the actuating wire is pulled to retract the outer sheath over the collapsed stent, the inner lumen must remain stationary, preventing the stent from moving axially within the body vessel.
Because proper positioning of the stent is critical to the performance of the stent, it is imperative that the physician knows exactly where the stent will be placed upon deployment.
What has been needed and heretofore unavailable is an improved device and method for accurately providing for release and deployment of stents, including self-expanding stents. The present invention satisfies these and other needs.
Briefly, and in general terms, the present invention is directed to a bio-compatible or bio-absorbable addition to a stent and/or stent delivery system. More particularly, the invention relates to a bio-compatible or bio-absorbable sheath, lining, or filament positioned on or in a stent. The bio-compatible or bio-absorbable material is designed to be implanted in the body along with the stent. After implantation, the material may be absorbed into the body, such as where the material is a bio-absorbable material that dissolves over a period of time.
In one embodiment of the invention, a bio-absorbable or bio-compatible filament is wound through or around an expandable stent. The filament may have sufficient strength to help in constraining the stent in an unexpanded configuration. Such a filament may still have sufficient weakness to permit the stent to be expanded via the application of a force, such as via the application of force provided by the expansion of a balloon catheter where the stent is positioned on the balloon. Expansion of the stent may be achieved by applying sufficient force to cause the filament to break or otherwise fail or relax. Expansion of the stent may be achieved by changing the configuration of the filament, such as by pulling or pushing, proximally or distally, on the filament until it no longer provides sufficient restraint to prevent the stent from expanding. The filament may be formed from various materials, including polymers. The filament may comprise one or more therapeutic agents, such as a drug useful in treating arterial walls.
Such a filament may be bonded to the delivery catheter and/or the stent, such as where a polymer filament is heat-bonded in a tightly-coiled position around the stent. During stent deployment, which may be achieved through inflation of a balloon catheter, the bonding of the filament to the stent and/or delivery catheter may fail, in whole or in part, loosening the tightness of the filament around the stent and permitting the stent to expand.
The filament maybe used to constrain self-expanding stents to prevent their expanding prior to the desired time and position for stent deployment. The filament may also be used with non-self-expanding stents, such as balloon-expandable stents, to help to retain the stent on a delivery system, such as a delivery catheter. The filament may also comprise and/or be used to deliver therapeutic agents, such as drugs or radiation therapy materials, or other materials that improve stent delivery, deployment, and/or performance, including materials that improve stent visibility under fluoroscopy or that facilitate radiation therapy.
In a further embodiment of the invention, the bio-compatible and/or bio-absorbable material forms a sheath and/or coating that surrounds the stent, in whole or in part. Like the filament, the sheath and/or coating may have sufficient strength to help in constraining the stent in an unexpanded configuration, and may still have sufficient weakness to permit the stent to be expanded by applying sufficient force to cause the sheath to break or otherwise fail and/or relax. The sheath and/or coating may be formed from various materials, including polymers, and may comprise one or more therapeutic agents. In the case of a coating that is bonded to the stent, the coating may be applied to the inner or outer surface of the stent.
In a further embodiment of the invention, the bio-compatible and/or bio-absorbable material is positioned in openings in the stent itself. For example, the material may be positioned to fill one or more of the openings in an expandable stent pattern. In stents that require such openings to change shape during stent expansion, the material may serve to prevent stent expansion by preventing the openings from changing shape. For example, the material may serve as an adhesive that holds the sides of the opening in close proximity to one another, thereby preventing the stent from expanding. The material maybe configured to fail or otherwise relax when sufficient force is applied to expand the stent, such as the force applied by inflation of a catheter balloon.


Devices, methods and systems for stabilizing at least a portion of the spinal column are provided. Devices include anchors and coupling members for engaging an elongate member. Systems include an elongate member sized to span a distance between at least two vertebral bodies and being at least partially formed of a flexible material. A number of anchors and coupling members are used to secure the elongate member to each of the vertebral bodies. The anchors can be compressed towards one another and the elongate member secured thereto and/or the elongate member can be tensioned to provide corrective forces to the spine.

The spine is subject to various pathologies that compromise its load bearing and support capabilities. Such pathologies of the spine include, for example, degenerative diseases, the effects of tumors and, of course, fractures and dislocations attributable to physical trauma. In the treatment of diseases, malformations or injuries affecting spinal motion segments (which include two or more adjacent vertebrae and the disc tissue or disc space therebetween), and especially those affecting disc tissue, it has long been known to remove some or all of a degenerated, ruptured or otherwise failing disc. It is also known that artificial discs, fusion implants, or other interbody devices can be placed into the disc space after disc material removal. External stabilization of spinal segments alone or in combination with interbody devices also provides advantages. Elongated rigid plates, rods and other external stabilization devices have been helpful in the stabilization and fixation of a spinal motion segment.
While the external stabilization systems of the prior art are a step in the right direction, there remains room for additional improvements. Oftentimes, the geometric and dimensional features of these systems and patient anatomy constrain the surgeon during surgery and prevent optimal placement, attachment and loading of the spinal motion segment.
Thus, there is a general need in the industry to provide methods and devices for stabilizing a spinal motion segment that reduce surgeon constraints during surgery and optimize placement and attachment of the stabilization devices to the spinal motion segment. There are also needed improved devices for connecting longitudinal members to the spinal column. There is also a need for stabilization devices that allow segmental motion to be maintained after attachment thereto. There are further needs for stabilization devices that maintain the desired corrective forces on the spinal motion segment. The present invention is directed to meeting these needs and others in a novel and unobvious manner.

This patent is subject to a terminal disclaimer.

Flexible spinal stabilization system and method


A plurality of detector rings in which detectors arranged densely or spatially in a ring shape or in a polygonal shape are arranged, with an open space kept in the body axis direction, coincidences are measured for some of or all of detector pairs connecting the detector rings apart from the open space to perform three-dimensional image reconstruction, thereby imaging the open space between the detector rings as a tomographic image. Therefore, the open space is secured, with the deteriorated quality of an image suppressed, thus making it possible to easily gain access to a patient under PET scanning from outside a gantry and also provide irradiation of particle beams for cancer treatment as well as X-ray CT scanning.

PET (Positron Emission Tomography) is a method for injecting radiopharmaceuticals labeled with a positron emission nuclide into the body to image the spatial and temporal distribution of the radiopharmaceuticals. In particular, PET scanning in which a radiopharmaceutical called fludeoxyglucose (FDG) is used has become the focus of attention because of the usefulness in making an early diagnosis of cancers over the entire body.
In PET, a radiopharmaceutical to be injected is selected to obtain information on various functions of the brain and organs. It was, however, difficult to accurately localize a site of cancer, if the cancer was found, due to the shortage of anatomical information. It is described that X-ray CT images are structural images, while PET images are functional images. In response to the above-described demands, PET/CT scanners capable of performing PET and X-ray CT scanning continuously on the same bed have been made commercially available from many companies, thus greatly contributing to the widespread use of FDG-PET.
On the other hand, it is also important to treat cancers found by a PET diagnosis or others. A method for treating cancers by using nuclear radiation, unlike conventional surgical procedures or chemotherapies has become the focus of attention. In particular, particle radiotherapy in which heavy ion particle beams or proton beams are irradiated only at a cancer site has gained a great deal of attention as a method for providing excellent therapeutic effects and characteristics of acutely concentrated irradiation to lesions. Irradiation is performed by controlling accurately the direction and dosage of beams according to treatment plans carefully calculated on the basis of X-ray CT images which have been taken separately. However, in reality, it is difficult to confirm accurately whether irradiation has been performed in accordance with treatment plans or not. If the patient is positioned wrongly to result in deviation of the irradiation field, the deviation is not easily detected. Therefore, a method in which PET is used to monitor the irradiation field of particle beams in real time is now gaining attention. According to this method, a PET radiopharmaceutical is not injected but annihilation radiation resulting from projectile fragmentation reactions or target nuclear spallation reactions by beam irradiation is imaged by using the principle of PET. Since a site at which the annihilation radiation is generated is strongly correlated with the dosage distribution of irradiation beams, this method is expected to monitor treatment.
The principle of PET is as follows. As shown in FIG. 1, positrons emitted from a positron emission nuclide 8 by the decay of positrons undergo pair annihilation with electrons in the vicinity, and the thus generated pair of annihilation (gamma) photons 8a, 8b at 511 keV are determined by a pair of radiation detectors 10a, 10b according to the principle of coincidence. Thereby, the position at which the nuclide 8 is present can be localized on one line segment connecting between the pair of detectors 10a, 10b (coincidence line: line-of-response: LOR). When an axis from the head of a patient to the feet is defined as a body axis, a distribution of the nuclide on a planar surface intersecting perpendicularly with the body axis is obtained by image reconstruction in two-dimensional mode from data of the coincidence line determined on the planar surface in various directions.
Therefore, as shown in FIG. 2 (A) covering a polygonal-type PET scanner and in FIG. 2 (B) covering a ring-type PET scanner, earlier PET scanners were provided with a constitution to arrange detectors 10 on a planar surface which was given as a field-of-view (FOV) in such a manner as to surround the FOV in a polygonal shape (A) or a ring shape (B). In FIG. 2 (B), numeral 6 depicts a patient and that of 11 depicts a detector ring.
In the 1990s, as illustrated in FIG. 3 (A) covering a multi-layer polygonal-type PET scanner and in FIG. 3 (B) covering a multi-layer ring-type PET scanner, 3-D mode PET scanners were developed one after another in which detector rings 11 were arranged in the body axis direction of the patient 6 to give a multiple ring 12, thereby a FOV in two-dimensional mode was changed to that in three-dimensional mode, and the coincidence was also determined between the detector rings 11 to increase the sensitivity greatly.
On the other hand, as illustrated in FIG. 4, gamma camera opposition-type PET scanners which rotate gamma cameras 14 arranged in opposition have also been developed. However, this type of PET scanner is insufficient in sensitivity due to the limited solid angle of a detector, with no widespread use. Positron imaging equipment in which cameras are not rotated has been commercially available mainly for experimental uses. The equipment is to obtain planar images parallel with the face of the detector and not for tomography (corresponding not to X-ray CT but to radiography in X-ray equipment).
In order to increase the resolution of an image in view of the principle of image reconstruction, it is necessary that coincidence lines are obtained densely.
The detector sensitivity of a PET scanner is important in increasing the accuracy of an image. The detector sensitivity is generally considered insufficient. In order to compensate for the insufficiency, the dosage of a injecting nuclide at about 5 mCi (=185 MBq) (an effective dosage equivalent to about 40 times higher than that used in X-ray photograph of the chest) and the scanning time which is long, about 30 minutes are required. These factors cause mental and physical burdens to patients and are also one of the reasons that medical institutions cannot lower examination costs.
Therefore, in order to increase the detection sensitivity, recently developed PET scanners tend to array detectors, with no clearance left therebetween, and also arrange them long in the body axis direction. A patient port 13 (refer to FIG. 3) is approximately about 60 cm in diameter and from 40 cm up to 100 cm long in the body axis direction.
However, there is such a problem that a long patient port further increases the closed nature of the port, thereby causing psychological stress to patients. In particular, a PET scanner is frequently used not only in cancer screening tests for healthy people but also in examinations for patients having various types of diseases including mental disorders. Therefore, it is strongly desired to reduce the psychological stress to patients. A situation in which a patient under PET scanning is not visually confirmed for health conditions is not desirable also for medical personnel who perform PET scanning. Further, in research for understanding brain functions, many experiments are conducted in which blood samples are taken at intervals of several minutes during PET scanning or visual stimulations are given to visualize reactions inside the brain by using PET. The long patient port causes problems in these experiments as well.
Further, where a PET scanner is used to monitor particle radiotherapy in real time, not only a site to be treated can be determined during the same session by the PET scanner but also a PET scanner is required to be high in sensitivity because annihilation radiation resulting from irradiation is at a trace amount as compared with the amount of nuclide injected on ordinary PET scanning. In order to realize the high sensitivity, detectors must be arranged densely and extensively. However, since the detectors are not to block particle beams, it was difficult to arrange the detectors on the PET scanner in such a manner as to meet simultaneously the above-described two conditions. In the Gesellschaft für Schwerionenforschung mbH (GSI) of Germany and the National Cancer Center (Hospital East) of Japan, the rotational opposition-type PET scanner shown in FIG. 5 (A) is used to monitor treatment. Gamma camera opposition-type PET scanners can be easily arranged so as not to block particle beams 22 irradiated from a therapeutic radiation controller 20 but definitely hold a disadvantage in that the detector sensitivity is fundamentally lower.
A research group in Germany has proposed a fixed slit-type PET scanner as shown in FIG. 5(B) in which a slit 12s is made on the side of a multilayer ring PET scanner for allowing beams to pass through, making evaluation based on the computer simulation. However, the slit lacks necessary information for image reconstruction because of the presence of the slit, resulting in the deteriorated quality of an image, which is regarded as a problem (P. Crespo, et al., "On the detector arrangement for in-beam PET for hadron therapy monitoring," Phys. Med. Biol. Journal, vol. 51 (2006) pp. 2143-2163).
FIG. 6 illustrates a representative constitution of a conventional PET/CT scanner (refer to U.S. Pat. No. 6,490,476 B1). In this drawing, the numeral 32 depicts an X-ray tube of the X-ray CT scanner 30, and the numeral 34 depicts an X-ray detector, both of which are rotated to perform scanning. There is now available a type in which each of the PET scanner and the X-ray CT scanner is provided with a completely independent gantry and a type in which they are housed into one gantry in an integrated manner. The PET scanner and the X-ray CT scanner may be arranged in a different order, depending on the type, but they are always arranged in tandem inside the gantry. In terms of the movement of a bed 7, there is a type in which a gantry moves with respect to a fixed bed and a type in which a bed moves with respect to a fixed gantry.
Whichever the type may be, in a conventional PET/CT scanner, a field of view (FOV) of the PET is not in agreement with that of X-ray CT, or is several dozen centimeters apart from each other. There is found a potential problem that the same site is not determined during the same session by PET and X-ray CT. In the conventional PET/CT scanner, a bed is moved relatively with respect to a gantry, that is, a temporal difference is given, by which the same site can be imaged by PET and X-ray CT. In currently available FDG-PET check-ups, scanning is performed in several minutes at each site due to the fact that a radiopharmaceutical moves slowly in the body and the sensitivity is lower. For this reason, the above-described temporal difference is not recognized as a problem. However, a discrepancy between PET images and X-ray CT images on the chest which entails the deformation by respiration is found. This discrepancy is now recognized as a serious problem.
Thanks to the recently advanced development of PET scanners and PET radiopharmaceuticals, new PET radiopharmaceuticals and PET scanners extremely high in sensitivity will become available. Therefore, increased demand can be expected for imaging the pharmacokinetics inside the body at a higher speed. In this instance, the above-described temporal difference may be recognized as a problem.
A FOV of the conventional PET scanner in the body axis direction is limited to about 20 cm. Therefore, a bed is moved over several dozen minutes intermittently or continuously to image an entire body of a patient. Therefore, a site apart at a greater distance than the FOV in the body axis direction cannot be imaged theoretically during the same session. Although there are problems such as complicated data processing, the greatest reason for the limited FOV in the body axis direction is the increased equipment cost due to a greater number of detectors. On the other hand, there is a strong demand for expansion of the FOV in the body axis direction. For example, the Research Institute for Brain and Blood Vessels Akita conducted research in which two commercially available PET scanners were arranged together to image brain and heart regions during the same session and independently from each other (H. Iida, et al., "A New PET Camera for noninvasive quantitation of physiological functional parametric images. HEADTOME-V-Dual.," Quantification of brain function using PET (eds. R. Myers, V. Cunningham, D. Bailey, T. Jones) p. 57-61, Academic Press, London, 1996).
In the above constitution, although the FOV in the body axis direction is expanded intermittently, an increasing number of detectors are installed to raise the cost. Further, since each of the PET scanners makes an independent coincidence determination, no detection can be made for the radiation from a nuclide present at a region between the scanners, thus resulting in a failure in imaging the region between the scanners.
In positron imaging equipment not for tomography but for planar imaging, an idea has been proposed that detectors are arranged at sparsely spaced clearances, thereby sampling of the coincidence line can be sparsely performed to increase the uniformity and also expand a FOV (Japanese Published Unexamined Patent Application No. Hei 9-211130 and Japanese Published Unexamined Patent Application No. 2001-141827).
However, where this idea is applied as it is to a PET scanner so that detectors are arranged sparsely on a ring, the coincidence line necessary for image reconstruction is lacking to inevitably result in the deteriorated quality of an image.
On the other hand, Japanese Published Unexamined Patent Application No. Hei 5-150046 has proposed a method in which a FOV different from that which is imaged by a PET scanner as a tomographic image is measured simply at low cost as a projected image. As illustrated in FIG. 7, this method assumes such a case that the head of a subject 101 is measured by using a PET scanner (detector 102) and the heart is measured during the same session for the conditions by using another device (detector 105). This method may have demand for an activation test or the like in which, for example, 15O-labeled water is injected to measure the change in local cerebral blood flow in response to stimulation. Images of the brain must be obtained as tomographic images. Regarding the heart, only monitoring of blood flow pumped by the heart will be sufficient. Therefore, this method is considered to assume that a PET scanner for obtaining tomographic images and positron imaging equipment for obtaining projected images are arranged in tandem. Specifically, the PET scanner needs the image reconstruction for obtaining tomographic images, while the positron imaging equipment does not need the image reconstruction because measured data in itself is a projected image. In this method, some of the detectors used in the PET scanner also act as detectors of the positron imaging equipment, thereby providing an advantage that these two sets of equipment are combined into one set of integrated equipment to reduce the cost. In FIG. 7, the numerals 103 and 106 depict coincidence circuits, and those of 104 and 107 depict data processors.
The above method is to expand a FOV, however, it may be considered to secure an open space from a different point of view. However, provided by the detector 5 is not a tomographic image but a projected image.
Japanese Published Unexamined Patent Application No. Hei 5-150046 has also proposed that a plurality of detectors 5 are arranged to pick up projected images at the same time in various directions but has not described a point where an image is reconstructed to obtain a tomographic image.

PET scanner and image reconstruction method thereof

National Institute of Radiological Sciences


A combined arterial and venous blood tubing set is provided for transport of blood between a patient and a blood processing unit. The set comprises an arterial set component comprising arterial tubing having an arterial patient connector at one end and an arterial unit connector at the other. A venous set component has venous tubing with a venous patient connector at one end and a venous unit connector at the other end. The arterial and venous patient connectors, and the arterial and venous unit connectors, are respectively, substantially, and releasably directly connected to each other. As a result of this, the arterial, and venous set components cooperate to form a loop. Other features of improved sets are also disclosed.

The field of blood processing primarily comprises hemodialysis and plasmapheresis, although other forms of blood treatment may also be used, for example, hemoperfusion, passing blood through adsorbent cartridges, and the like. To accomplish this, blood sets are used to convey blood from the patient to a blood processing device, and then to return the blood from the device back to the patient. The former blood set is called the arterial set, while the latter set is called the venous set.
In combination, the arterial and venous sets comprise several yards of tubing, and thus are rather cumbersome to handle. Furthermore, cost is of course a critical matter, especially when a patient has a chronic need for treatment as in hemodialysis, so that even small cost savings can add up to a substantial amount over a year or more of repeated usage of disposable arterial and venous sets.
Furthermore, priming of the sets is an issue requiring the skilled attention of technicians, so that any improvement or simplification in the priming process, and other processes of use of the arterial and venous sets, can be valuable.
By this invention, numerous improvements to conventional arterial and venous blood sets are provided for reduction of cost and improved ease and efficiency of use.
By this invention, a combined arterial and venous blood tubing set may be provided for the transport of blood between a patient and a blood processing unit. The combined set comprises an arterial set component which comprises arterial tubing having an arterial patient connector at one end and an arterial unit connector at the other end. A venous set component of the set comprises venous tubing having a venous patient connector at one end and a venous unit connector at the other end.
In accordance with this invention, the arterial and venous patient connectors, and the arterial and venous unit connectors, are respectively substantially and releasably directly connected to each other in such manner that the arterial and venous set components cooperate to form a loop.
This facilitates the installation of the-sets into a hemodialysis machine, for example, resulting in greater ease of installation with a saving of time. Eventually, the set components wind up serving in the normal manner of arterial and venous sets. Even with a relatively small increase or improvement in ease and time saving, the improvement can be quite substantial particularly in the treatment of chronic conditions, as in most hemodialysis, so that the effect of the improvement in time savings can add up to a substantial amount over the course of a year.
Particularly, the arterial and venous unit connectors may be directly connected together with a frangible seal, to permit their breaking apart after the combined set has been primed, for subsequent connection to a blood processing unit.
Thus, the fully primed arterial and venous sets may be directly connected to a reused dialyzer. Solution may then be circulated through the system with air being removed from the dialyzer, but no air being sent to the dialyzer through the primed sets, which reduces the number of air bubbles being trapped within the dialyzer itself. Air coming from the dialyzer will then be typically removed by a bubble trap in the sets, so that it is not recirculated again to the dialyzer.
By this invention, particularly wet, reused dialyzers (or other blood processing devices) can be effectively primed to exhibit improved performance because of a reduced number of trapped air bubbles within the membrane system of the dialyzer.
The arterial and venous patient connectors of the respective arterial and venous sets may optionally be substantially directly connected together by an interconnector tube to permit circulatory priming of the arterial and venous sets, and also to avoid the need of other end closures at the arterial and venous patient connectors, if the arterial and venous sets are supplied to the user in interconnected form as in this invention.
The interconnector tube preferably comprises a tube having a connector such as a female luer connector at each end, for connection with the patient connectors of the arterial and venous sets. Also, the tube may have an attached, integral cap to close an end of the tube after disconnection of one of the patient connectors. Thus, one of the patient connectors may have its sterility preserved while the other patient connector is being attached to a fistula set and access to the patient""s bloodstream is being obtained.
Priming of the connected arterial and venous sets can be performed in a manner similar to that disclosed in Utterberg U.S. Pat. No. 5,951,870, preferably with the modifications described below:
The arterial and venous sets respectively preferably have the substantially directly connected end connectors to form a closed loop as described above. One may pass priming solution into and through a portion of the directly connected arterial and venous sets in a first direction that is reversed to the normal direction of blood flow through the sets, while removing air from one of the sets through a branching port from one of the sets.
One also may pass priming solution into a second direction of flow opposite to the first flow direction through the system (which opposite direction is the normal direction of flow through the system) while continuing to remove air from the system through the port, until substantially all air desired is removed from the arterial and venous sets.
Thereafter, with the flow stopped temporarily the unit arterial and venous connectors are separated and connected to the blood processing unit such as a dialyzer preferably with the blood outlet at the top to facilitate bubble removal. One then pumps the priming solution through the arterial and venous sets and the blood processing unit in the second flow direction (i.e., the normal flow direction which is reversed to the first flow direction), to flush the sets and blood processing unit, without passing substantial amounts of air into the blood processing unit.
This method can be accomplished while pumping the solution with a flow pump such as a roller pump through the set, which operates in only a single, pumped flow direction throughout the entire priming process, the normal, second flow direction described above. The first flow direction, which is reverse to the second flow direction, may take place by gravity flow if desired. Preferably, the arterial and venous patient connectors are substantially directly connected together throughout substantially all of the performance of the above method.
The invention also pertains to a tubular medical fluid set having an in-line bubble trap chamber having a top wall. The top wall defines a port which communicates with flow tubing of the tubular set. The port communicates with a port tube which extends into the chamber and has a tube end which is spaced below the top wall, and preferably below the intended blood/air interface. The tube end defines a wall that directs flow out of the tube circumferentially into and through the bubble trap chamber. Thus, blood entering the chamber through the tube is directed circumferentially about the chamber wall, the effect of which is to direct bubbles radially inwardly, rather than downward.
The chamber also preferably defines a baffle to convert circumferential flow into turbulent flow at positions above the tube end wall and the circumferentially directed blood and at the blood-air interface. This prevents formation of a blood whirlpool having a significant, centrally depressed upper surface. Thus, the centrally disposed bubbles will rise to the top of the chamber to join an air space that is typically present there, without being sucked downwardly as would be caused by the presence of such a blood whirlpool having a centrally depressed upper surface.
Accordingly, the flow pattern of blood near the top of the bubble trap chamber described comprises a top segment of largely turbulent blood flow, and a lower segment of largely circumferential blood flow.
As another aspect of this invention, priming of a tubular medical fluid set may take place, the set having an in-line bubble trap chamber, preferably on the venous set. One passes priming solution into the tubular set preferably at a point pre-pump on the arterial set and bubble trap chamber, while withdrawing air from the set through a port in an upper portion of the chamber. The port communicates with a port tube extending into the chamber in positions which are spaced below a top chamber wall.
Further in accordance with this invention, preferably the in-line bubble trap chamber has an upper portion which defines a port that communicates with the exterior. The port communicates with a port tube extending into the chamber, having a port tube opening spaced below the top wall within the chamber, to automatically define a predetermined air volume and liquid level in the chamber approximately at or above the tube opening as the tubular set is filled with priming solution.
The bubble trap chamber top wall also may define an axially depressed portion which, in turn, defines a needle pierceable, resealable injection site to permit an injection needle of at least about xc2xd inch needle length to penetrate said injection site and to communicate with liquid below said liquid level which preferably is set by the port tube arrangement mentioned above. contrary to the prior art, this injection site carried on the top wall of a bubble trap chamber resides at a lower position from other portions of the top wall, providing a desired inner volume under the other portions for air above a liquid level. In combination with this, the resealable injection site is carried on the axially depressed portion of the top wall, so that the injection site is closer to the liquid level within the bubble trap chamber, preferably permitting an injection needle of at least about xc2xd inch needle length to penetrate the injection site and to communicate with the liquid below the liquid level, while still permitting an air volume within the bubble trap chamber of preferably at least about 4 cc. This permits direct access to the blood by a conventional hypodermic needle from the top of the chamber, for blood sampling from the chamber injection site, permitting infusion of the very expensive drug erythropoietin (xe2x80x9cEPOxe2x80x9d), with pump flushing of the needle several times, drawing blood into the needle and out again to rinse all possible EPO into the set and then the patient, to avoid wasting of the highly valuable material.
Further in accordance with this invention, a tubular blood set for transfer of blood between a patient and a blood treatment device has main blood flow tubing and a flexible branch tube connected in branching relation to the main tubing. The branch tube is adapted for connection at its other end to a source of physiological, cell-free solution, as is conventional.
As particularly shown in Utterberg et al pending patent application Ser. No. 09/203,274, filed Dec. 1, 1998, some of the blood passing through the main blood flow tubing may extend into the branch tube to form a blood-solution interface, so that a pressure monitor which is also connected to the branch tube is protected from contact with blood by the presence of an amount of cell-free solution in the branch tube and a non-compressible, air-free pressure sensing path is provided through the cell free solution and the blood across the interface.
In accordance with this invention, to suppress pressure pulses from the main blood line tending to disrupt the blood-solution interface, a portion of the flexible branch tube is equipped with pulse suppression means. Such means may comprise a partially collapsible portion of the branch tube, a ball valve, a duckbilled valve or the like. The required aspects of the flattened tube or valve are that relatively unrestricted flow is allowed from an attached saline bag to the bloodline but flow from the blood line to the branch tube is suppressed progressively as the negative pressure in the blood line increases. To preferably accomplish this, the pulse-suppressing portion of the flexible branch tube is substantially flattened. Accordingly, this tube portion has a lumen that can and does reduce its cross-sectional area responsive to negative pressure in that area to a degree substantially greater than cylindrical tubing. This results in the suppression of negative pressure pulses created by the pumping of blood through the main flow tubing, which negative pressure pulses tend to disrupt the blood-solution interface in the branch tube. However, if the tube portion that is flattened is preferably placed in the branch tube between the blood-solution interface and the main blood flow tubing, the effect of these negative pressure pulses is damped at the interface area. However, the tube portion, or an alternative valve, can increase its cross-sectional area at any time responsive to positive pressure. Thus, if there is an urgent need to provide saline solution to the extracorporeal blood flow path in the event of a crisis, the tube portion or valve can expand back to its normal cylindrical shape or seating of the valve is less, so that increased solution flow can pass therethrough.
The flattened branch tube portion may comprise a flattened lumen cross section that defines a periphery having at least one open groove, which is transverse to the cross section, to avoid complete closing of the branch tube under negative pressure. Furthermore, a generally cylindrical, flexible branch tube may be used, the tube being flattened at the tube portion by a removable slide clamp which comprises a pair of arms defining a slot between them. The tube portion resides in the slot and, as is preferable, at least one of the arms defines a transversely extending groove that forms the open groove in the tube portion.
Further in accordance with this invention, a protector for a female luer connector is provided, which comprises: an outer sleeve, a central transverse wall defined in the outer sleeve, a male luer projecting axially within the sleeve from the transverse wall to engage the female luer connector along with the sleeve. A tube projects axially within the sleeve from the transverse wall into the direction opposed to the male luer. The tube and the male luer have connected lumens, with the tube having an outer end that is substantially recessed within the sleeve.
Accordingly, a female luer connector may be used as a air venting and/or drain line during priming, for example, with accordance with the teaching of Utterberg U.S. Pat. No. 5,951,870. However, after priming, rather than closing off this line it can be used for the addition of supplemental medication, added solution, or the like because the female luer connector on the end can have its sterility retained by the protector of this invention.
Specifically, the protector of this invention has an outer sleeve inner wall which has screw threads or preferably is free of screw threads. The sleeve inner wall preferably defines axially extending ribs at least on the side of the transverse wall that carries the male luer, to facilitate axially sliding connection and retention with the female luer connector. Furthermore, it is preferred for the tube outer end, which does not need to carry a taper like a male luer, to terminate at a point no more than about two thirds of the distance from the transverse wall to the end of the outer sleeve which is opposed to the male luer, so that this tube serves as a spout for the venting of air and priming solution, and is retained in aseptic condition, since it is recessed in the outer sleeve and thus protected.
Also, it is preferred for a hinged cap to be attached to the outer sleeve in a position which permits closure of the cap over the outer sleeve end that is opposed to the male luer , for preservation of aseptic conditions between priming and subsequent use of the female luer connector.
Thus, sets for blood processing are provided which exhibit significant distinction and advantage over the prior art.


A method of stripping silver from a printed circuit board without attacking the underlying base metal. The stripping solution comprises an oxidizing agent, an alkaline pH adjuster, and a silver solubilizing agent. After the silver has been sufficiently removed from the surface of the printed circuit board, the printed circuit board is contacted with a neutralization solution to remove any smut remaining on the surface. The silver stripping solution does not contain cyanide or chromium and does not require the use of anodic current.

This invention relates to a method of treating a printed circuit board to chemically remove plated silver from a printed circuit board without the use of harmful chemicals or the application of external current.
In the manufacture of electronic equipment utilizing printed circuits, connections of electronic components to the printed circuits are made by soldering of the leads of the components to the through-holes, surrounding pads, lands, and other points of connections.
To facilitate this soldering operation, the printed circuit fabricator is required to arrange that the through-holes, pads, lands, and other points of connection are receptive to the subsequent soldering processes. Thus, these surfaces must be readily wettable by the solder and permit an integral conductive connection with the leads or surfaces of the electronic components. Because of these needs, printed circuit fabricators have devised various methods of preserving and enhancing the solderability of surfaces.
Soldering directly to copper surfaces has been difficult and inconsistent. These problems are due mainly to the inability of keeping the copper surfaces clean and free of oxidation throughout the soldering operation. Immersion silver deposits have been found to provide excellent solderability preservatives, which are particularly useful in the fabrication of printed circuit boards. The soluble source of silver ions can be derived from a variety of silver compounds. An example of a silver immersion plating process can be found in U.S. Pat. No. 6,200,451, to Redline et al., the subject matter of which is hereby incorporated by reference. The immersion silver solution is used to plate a thin layer of silver onto the surface to be soldered. The resultant silver coating is generally between 1 and 100 micro-inches in thickness for effective enhancement and preservation of the solderability of the surface.
In general, an immersion plating process results from a replacement reaction whereby the surface being plated dissolves into solution and at the same time the metal being plated deposits from the plating solution onto the surface. The immersion plating initiates without prior activation of the surfaces. The metal to be plated is generally more noble that the surface metal. Thus, immersion plating is usually significantly easier to control and significantly more cost effective than electroless plating, which requires sophisticated auto catalytic plating solutions and processes for activation of the surfaces prior to plating.
In the course of fabricating a printed circuit board, it may also be necessary to afterwards strip the silver from all or selected copper, or other metal, surfaces over which it was deposited. This need arises, for example, where it is necessary to plate another metal, such as nickel or gold, directly over the copper at certain portions of the board, or where it is desired to apply a solder mask over certain bare copper surfaces. It also may be necessary to strip silver from the copper layer in the course of treating a reject piece in order to recover and reuse the underlying copper material.
It is well known in the art of stripping silver to use chemicals such as cyanides, chromates, and strong acid solutions to facilitate the removal of silver from the surface of a substrate. In addition it is well known to use an anodic current to facilitate the removal of silver, with or without the use of such chemicals.
Examples of useful silver strippers are inhibited acid or cyanide solutions. The acids include sulfuric and sulfonic acids and other mineral acids useful in metal stripping compositions. The cyanide stripper compositions include alkali or alkaline earth metals or ammonium cyanide stripping compositions known to those in the art. The inhibited compositions typically are inhibited by nitrocompounds. Examples of useful inhibiting compounds include nitrobenzenes, nitrobenzoic acids, nitrobenzaldehydes, nitroparafins, and nitroalkanes.
While these methods do facilitate the removal of plated silver, these methods are unacceptable due to environmental concerns relating to the use of cyanide or chromate. The chemicals used in the prior art also have a tendency to attack the underlying solder mask or substrate. In addition, there may be an inability, when using an anodic current, to apply current across the entirety of the printed circuit board.
U.S. Statutory Invention Registration H1,136, to Janikowski, the subject matter of which is hereby incorporated by reference, discloses a method for electroplating silver which comprises a plating solution and/or stripping solution of an alkali hydroxide and ethylenediamine. While the plating and/or stripping solution does not contain cyanide, the process of the invention does require an anodic current.
Likewise, U.S. Pat. No. 5,002,649, to Smith, the subject matter of which is hereby incorporated by reference, discloses an apparatus for electrolytically or chemically stripping plating material, including silver plating, from a selected surface. The apparatus requires anodic current, although the stripping can be accomplished either electrolytically or chemically. In addition, the chemical stripping solution may contain cyanide.
The method of the present invention provides a new stripping solution for removing silver that does not contain any of the more toxic chemicals of prior art stripping solutions or require the use of an anodic current to facilitate removal of the plated silver. In addition, the silver stripping solution of the present invention does not attack either the base metal to which the silver is plated or the solder mask. The method provides an inventive stripping solution to chemically remove plated silver from printed circuit boards without the problems inherently found in the prior art.
The present invention relates to a method of stripping silver from a printed circuit board without attacking the underlying base metal. Another benefit of the method of the present invention is its ability to selectively remove silver without attacking the solder mask.
The present invention comprises a method for removing plated silver from a printed circuit board comprising the steps of:
(a) contacting said printed circuit board with a stripping solution comprising an oxidizing agent, an alkaline pH adjuster, and a silver solubilizing agent; and
(b) neutralizing said printed circuit board with a neutralization solution.

Method of stripping silver from a printed circuit board