A free-flowing solid which does not self-ignite, comprising:

The present invention relates to a solid which does not self-igniting, comprising:
a) at least one support component,
b) at least one chemical compound which per se is self-igniting,
c) at least one inert liquid and
d) further components if desired.
The present invention additionally relates to processes for preparing a solid which does not self-ignite and to the use of such a solid for catalytic or stoichiometric carbon-carbon bond linking or for hydrogenation.
It has long been known, and is frequently desirable, to fix reactive, chemical compounds chemically or physically on support materials and thereby to enhance their suitability for particular chemical processes. Examples of important industrial-scale chemical processes are polymerization, hydrogenation or the drying of fluids, for example liquids or gases.
In polymerization processes, for example, especially in the production of polyolefins, use is made of solid, support-bound Ziegler, Phillips or metallocene catalyst systems. A common feature of these catalysts is that they include generally pyrophoric constituents, with the result that the catalysts may spontaneously ignite, especially under oxidizing conditions, for example on the ingress of air.
The self-ignitability of the solids, demonstrated by way of example in polyolefin catalysts, hinders or even prevents totally their use in large-scale industrial processes, since for safe working it necessitates special protective measures, which are often expensive and technically complex.
In addition, the classification of these solids, especially the polyolefin catalysts, as self-igniting substances greatly limits their transportation; for example, rapid despatch by air freight is not permitted.
WO 95/07939, WO 87/03889, WO 93/23439 and WO 94/28034 disclose the preparation of support-bound metallocene catalysts in suspension, subsequent removal of the solvent and drying of the solid to give a free-flowing catalyst. WO 93/23439 specifies drying as an essential step to obtain catalysts having advantageous properites. The dried catalysts of the prior art have the disadvantage that they are self-igniting.
Wetting of the dry solids, especially the polymerization catalysts, leads in general to unwanted properties in the catalysts, such as reduced polymerization activity, or formation of lumps which are difficult to meter.
It is an object of the present invention, therefore, to provide solids, especially flowable polyolefin catalysts, which are not self-igniting and which are virtually unimpaired in their other relevant properties.
We have found that this object is achieved by a solid which does not self-ignite, comprising:
a) at least one support component,
b) at least one chemical compound which per se is self-igniting,
c) at least one inert liquid and
d) further components if desired.
This solid is referred to below as xe2x80x9cnovel solidxe2x80x9d. We have also found a process for preparing a novel solid where the components a) to d) are mixed and then some of component c) is removed. We have also found a process for preparing a novel solid where components a) to d) are mixed, then virtually all of component c) is removed, and then a component c) is added to the dry solid again in an amount such that this solid does not self-ignite. We have also found that the novel solid can be used for catalytic or stoichiometric carbon-carbon bond linkage or for hydrogenation or drying of liquids.
There is broad scope for variation in the support component a). All organic or inorganic solids are suitable in general, especially those that are porous. Examples of particularly suitable inorganic support components a) are particulate oxides or salts. Examples of particularly suitable organic support components a) are particulate polymers.
Examples of particulate organic support material a) are polyolefins such as polyethylene, polypropylene, poly-1-butene and polymethyl-1-pentene and copolymers with the monomers on which these polymers are based, and also polyesters, polyamides, polyvinyl chloride, polyacrylates, polymethacrylates and polystyrene. However, preference is given to particulate inorganic support materials a), such as porous oxides, for example SiO2, Al2O3, MgO, ZrO2, TiO2, B2O3, CaO and ZnO. Metal halides, such as MgCl2, are other suitable supports. The support materials a) preferably have a particle diameter of from 1 to 300 xcexcm, in particular from 30 to 70 xcexcm. Examples of particularly preferred supports are silica gels, preferably those of the formula SiO2.aAl2O3, in which a is a number in the range from 0 to 2, preferably from 0 to 0.5; ie. aluminosilicates or silicon dioxide. Products of this kind are obtainable commercially, for example Silica Gel 332 from Grace.
There is likewise broad scope for variations in the component b) which per se is self-igniting and is defined by its property of self-ignition. Self-ignition is defined by the UN Recommendations Section 14.3 and EEC Directive 92/69, A 13, as described at length in the Examples. Examples of compounds which fall within this definition are organometallic compounds, metal hydrides or organometal hydrides, principally those of groups 1, 2, 3, 4, 5, 6, 12, 123, 13, 14 and 15 of the Periodic Table of the Elements (group numbering in accordance with the 1985 IUPAC Recommendation). Examples of particularly suitable components b) are lithium organyls, aluminum organyls and boron organyls. Preference is given to open-chain or cyclic alumoxane compounds which according to U.S. Pat. No. 4,794,096 can be obtained by reacting aluminum trialkyls with water. They are composed of from 5 to 30 structural units "Brketopenst"O Al(R1)"Brketclosest" connected in chain form or cyclic form, in which each R1 is a C1-C4-alkyl, preferably methyl or ethyl. The alumoxane compounds can also be present in a mixture with other metal alkyls, preferably with aluminum alkyls.
Also used are aluminum organyls of the formula Al(Rxe2x80x2)3, in which Rxe2x80x2 is hydrogen, C1-C10-alkyl, preferably C1-C4-alkyl, especially methyl, ethyl or butyl. Rxe2x80x2 can also be arylalkyl or alkylaryl each of 1 to 10 carbons in the alkyl and 6 to 20 carbons in the aryl. Also suitable are aluminum alkyls Al(Rxe2x80x2)3 in which Rxe2x80x2 can be fluorine, chlorine, bromine or iodine, with the proviso that at least one radical Rxe2x80x2 is a C-organic radical or hydrogen. Particularly preferred compounds are trimethylaluminum, triethylaluminum, triisobutylaluminum, diisobutylaluminum hydride and diethylaluminum chloride.
The components b) can be employed alone or as mixtures in the novel solid, the proportions of the mixture not being critical.
The components b) are generally applied by impregnating the support solid with the liquid and/or dissolved components b). Solvents suitable for this purpose are in general those which constitute component c). Component c) is an inert liquid, in other words a chemical compound which is liquid under standard conditions and which under standard conditions does not undergo, or undergoes only very slowly, chemical reaction with component b), with partial or complete chemical conversion of component b), in general decomposition, or with its own partial or complete chemical conversion. Partial chemical conversion is generally not the case until more than about 10 mol-%, preferably 3 mol-% and, in particular, 1 mol-% of the pure substance c) employed has been converted.
Highly suitable compounds for use as component c) are inert organic compounds such as aliphatic, isocyclic or aromatic hydrocarbon carbons. Examples are n-hexane, n-heptane, n-octane, isododecane, cyclohexane, toluene, ethylbenzene, 1-hexene, 1-pentene, 1-heptene and 1-octene, preferably n-heptane. It is of course also possible to use mixtures or isomers of these compounds as component c), especially those which are offered commercially, such as EC 180 from Shell or Isopar from Exxon.
The content of the liquid c) in the novel solid comprising a) to c) and optionally d) is such that c) is just no longer self-igniting but is still flowable, ie. contains virtually no coarse components. In accordance with our current state of knowledge, the amount of the liquid c) depends inter alia on the propensity to self-ignition of component b).
The novel solid usually comprises from 10 to 70% by weight, based on the solid not containing c), of c), preferably from 25 to 60% by weight and, in particular, from 30 to 40% by weight of c), as determined by the method of gas chromatography.
Polymerization catalysts, preferably olefin polymerization catalysts, based on the novel solid normally comprise a transition metal component d) as well.
Examples of particularly suitable transition metal components d) are the halides, preferably the chlorides, or alkoxides, preferably methoxides, ethoxides or isopropoxides, of the transition metals titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum and tungsten. Very particularly preferred components d) are metallocene complexes, ie. transition metal compounds having at least one cyclopentadienyl ligand or at least one ligand derived from the cyclopentadienyl structural unit.
Particularly suitable metallocene complexes are those of the formula I
where
M is titanium, zirconium, hafnium, vanadium, niobium or tantalum,
X is fluorine, chlorine, bromine, iodine, hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl having 1 to 10 carbons in the alkyl and 6 to 20 carbons in the aryl, xe2x80x94OR7 or xe2x80x94NR7R8, where
R7 and R8 are C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each of 1 to 10 carbons in the alkyl and 6 to 20 carbons in the aryl,
R2 to R6 are hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl which in turn may carry a C1-C10-alkyl as substituent, C6-C15-aryl or arylalkyl, where two adjacent radicals may together be saturated or unsaturated cyclic groups of 4 to 15 carbons, or are Si(R9)3 where
R9 is C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl,
Z is X or
xe2x80x83where
R10 to R14 are hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl which may in turn carry a C1-C10-alkyl as substituent, C6-C15-aryl or arylalkyl and where two adjacent radicals together may be saturated or unsaturated cyclic groups of 4 to 15 carbons, or are Si(R15)3 where
R15 is C1-C10-alkyl, C6-C15-aryl or C3-C10-cycloalkyl, or where the radicals R5 and Z together form a group xe2x80x94R16xe2x80x94Axe2x80x94in which
R16 is
xe2x80x83xe2x95x90BR17, xe2x95x90AlR17, xe2x80x94Gexe2x80x94, xe2x80x94Snxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x95x90SO, xe2x95x90SO2, xe2x95x90NR17, xe2x95x90CO, xe2x95x90PR17 or xe2x95x90P(O)R17,
xe2x80x83where
R17, R18 and R19 are identical or different and are hydrogen, halogen, C1-C10-alkyl, C1-C10-fluoroalkyl, C6-C10-fluoroaryl, C6-C10-aryl, C1-C10-alkoxy, C2-C10-alkenyl, C7-C40-arylalkyl, C8-C40-arylalkenyl or C7-C40-alkylaryl or where two adjacent radicals in each case with the atoms linking them form a ring, and
M2 is silicon, germanium or tin,
A
xe2x80x83where
R20 is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl, alkylaryl or Si(R21)3,
R21 is hydrogen, C1-C10-alkyl, C6-C15-aryl which may in turn be substituted by C1-C4-alkyl, or is C3-C10-cycloalkyl
or where the radicals R5 and R13 together form a group xe2x80x94R16xe2x80x94. of the metallocene complexes in formula I, preference is given to
Preference is given to those transition metal complexes which contain as ligands two, possibly bridged, aromatic ring systems, ie. in particular the transition metal complexes of the formulae Ib and Ic.
The radicals X can be identical or different but are preferably identical.
Of the compounds of the formula Ia, particular preference is given to those where
M is titanium, zirconium or hafnium,
X is chlorine, C1-C4-alkyl or phenyl, and
R2 to R6 are hydrogen or C1-C4-alkyl.
Of the compounds of the formula Ib, in those which are preferred
M is titanium, zirconium or hafnium,
X is chlorine, C1-C4-alkyl or phenyl,
R2 to R6 are hydrogen, C1-C4-alkyl or Si(R9)3 and
R10 to R14 are hydrogen, C1-C4-alkyl or Si(R15)3.
Particularly suitable compounds are those of the formula Ib in which the cyclopentadienyl radicals are identical.
Examples of particularly suitable compounds include:
bis(cyclopentadienyl)zirconium dichloride,
bis(pentamethylcyclopentadienyl)zirconium dichloride,
bis(methylcyclopentadienyl)zirconium dichloride,
bis(ethylcyclopentadienyl)zirconium dichloride,
bis(n-butylcyclopentadienyl)zirconium dichloride and
bis(trimethylsilylcyclopentadienyl)zirconium dichloride
and also the corresponding dimethylzirconium compounds.
Of the compounds of the formula Ic, particular suitability is possessed by those where
R2 and R10 are identical and are hydrogen or C1-C10-alkyl,
R6 and R14 are identical and are hydrogen, methyl, ethyl, isopropyl or tert-butyl,
R3, R4, R11 and R12 are defined as follows:
R4 and R12 are C1-C4-alkyl,
R3 and R11 are hydrogen,
or two adjacent radicals R3 and R4 and R11 and R12 together are cyclic groups of 4 to 12 carbons,
R16 is
M is titanium, zirconium or hafnium and
X is chlorine, C1-C4-alkyl or phenyl.
Examples of particularly suitable complex compounds include
dimethylsilanediylbis(cyclopentadienyl)zirconium dichloride,
dimethylsilanediylbis(indenyl)zirconium dichloride,
dimethylsilanediylbis(tetrahydroindenyl)zirconium dichloride,
ethylenebis(cyclopentadienyl)zirconium dichloride,
ethylenebis(indenyl)zirconium dichloride,
ethylenebis(tetrahydroindenyl)zirconium dichloride,
tetramethylethylene-9-fluorenylcyclopentadienylzirconium dichloride,
dimethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)-zironium dichloride,
dimethylsilanediylbis(3-tert-butyl-5-ethylcyclopentadienyl)-zirconium dichloride,
dimethylsilanediylbis(2-methylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-isopropylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-tert-butylindenyl)zirconium dichloride,
diethylsilanediylbis(2-methylindenyl)zirconium dibromide,
dimethylsilanediylbis(3-methyl-5-methylcyclopentadienyl)-zirconium dichloride,
dimethylsilanediylbis(3-ethyl-5-isopropylcyclopentadienyl)-zirconium dichloride,
dimethylsilanediylbis(2-methylindenyl)zirconium dichloride,
dimethylsilanediylbis(2-methylbenzindenyl)zirconium dichloride
dimethylsilanediylbis(2-ethylbenzindenyl)zirconium dichloride,
methylphenylsilanediylbis(2-ethylbenzindenyl)zirconium dichloride,
methylphenylsilanediylbis(2-methylbenzindenyl)zirconium dichloride,
diphenylsilanediylbis(2-methylbenzindenyl)zirconium dichloride,
diphenylsilanediylbis(2-ethylbenzindenyl)zirconium dichloride,
and dimethylsilanediylbis(2-methylindenyl)hafnium dichloride
and also the corresponding dimethylzirconium compounds.
Of the compounds of the formula Id, those which are to be mentioned as being particularly suitable are those where
M is titanium or zirconium,
X is chlorine, C1-C4-alkyl or phenyl,
R16 is
A is
xe2x80x83and
R2 to R4 and R6 are hydrogen, C1-C10-alkyl, C3-C10-cycloalkyl, C6-C15-aryl or Si(R9)3, or where two adjacent radicals are cyclic groups of 4 to 12 carbons.
Complex compounds of this kind can be synthesized by methods known per se, with preference being given to the reaction of the appropriately substituted, cyclic hydrocarbon anions with halides of titanium, zirconium, hafnium, vanadium, niobium or tantalum.
Examples of corresponding preparation techniques are described, inter alia, in the Journal of organometallic Chemistry, 369 (1989), 359-370.
It is also possible to employ mixtures of different metallocene complexes.
The novel solid, and especially the polymerization catalysts based on it, may additionally include, as component d), a compound which forms metallocenium ions. This can be selected either from the group of the compounds b), preferably aluminoxanes and especially methylaluminoxane, or from the group of the following compounds, if desired in addition to b).
Suitable compounds which form metallocenium ions are strong, neutral Lewis acids, ionic compounds with Lewis-acid cations, and ionic compounds with Brxc3x6nsted acids as cation.
Preferred strong, neutral Lewis acids are compounds of the formula II
M3X1X2X3xe2x80x83xe2x80x83II
where
M3 is an element from main group III of the Periodic Table, especially B, Al, Ga preferably B, and
X1, X2 and X3 are hydrogen, C1- to C10-alkyl, C6- to C15-aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl each having 1 to 10 carbons in the alkyl and 6 to 20 carbons in the aryl, or are fluorine, chlorine, bromine or iodine, and in particular are haloaryls, preferably pentafluorophenyl.
Particularly preferred compounds of the formula II are those in which X1, X2 and X3 are identical, preference being given to tris(pentafluorophenyl)borane.
Suitable ionic compounds with Lewis-acid cations are compounds of the formula III
[(Ya+)Q1Q2 . . . Qz]d+xe2x80x83xe2x80x83III
where
Y is an element from main groups I to VI or from subgroups I to VIII of the Periodic Table,
Q1 to Qz are radicals with a single negative charge such as C1-C28-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl each of 6 to 20 carbons in the aryl and 1 to 28 carbons in the alkyl, or are C1-C10-cycloalkyl which may be substituted by C1-C10-alkyls, or are halogen, C1-C28-alkoxy, C6-C15-aryloxy, silyl or mercaptyl groups,
a is an integer from 1 to 6,
z is an integer from 0 to 5, and
d corresponds to the difference a-z but is greater than or equal to 1.
Carbonium cations, oxonium cations, and sulfonium cations, and cationic transition metal complexes, are particularly suitable. Particular mention may be made of the triphenylmethyl cation, the silver cation and the 1,1xe2x80x2-dimethylferrocenyl cation. They preferably possess noncoordinating counterions, especially boron compounds as are specified in WO 91/09882, preferably tetrakis (pentafluorophenyl) borate.
Ionic compounds with Brxc3x6nsted acids as cations and preferably likewise noncoordinating counterions are specified in WO 91/09882; a preferred cation is N,N-dimethylanilinium.
Suitable processes for preparing the novel solid are the following.
Support solid a), preferably a porous inorganic oxide, especially silica gel, is suspended in the inert liquid c), preferably an aliphatic, isocyclic or aromatic hydrocarbon, especially heptane and/or toluene. The component b), preferably an organometallic compound from group 3 of the Periodic Table of the Elements or an aluminoxane, as defined above, preferably methylaluminoxane, or else a mixture of components b) and d), which may also react chemically with one another, is added to the suspension. Components b) and, if desired, d) can also be present as solutions, preferably in inert organic solvents, such as aliphatic, isocyclic hydrocarbons or aromatic hydrocarbons, ie. n-hexane, n-heptane, isododecane, toluene or ethylbenzene. The temperatures for this reaction are not critical. Components a), b) and c) and, if used, d) are usually reacted at from xe2x88x9270 to 120xc2x0 C., preferably at from 0 to 50xc2x0 C.
Subsequently, virtually all of the solvent c) can be removed and the solid which remains is dried, usually at from 20 to 120xc2x0 C., and a defined amount of component c) is added (variant A), or else the amount of component c) in the novel solid can be established at the desired level by incomplete removal (variant B). The liquid c) added in variant A can, but need not, be chemically identical to the liquid c) originally present in the mixture.
A highly suitable process for preparing a solid polymerization catalyst, preferably for olefin polymerization, which is not self-igniting is the following.
Support solid a), preferably a porous inorganic oxide, especially silica gel, is suspended in the inert liquid c), preferably an aliphatic, isocyclic or aromatic hydrocarbon, especially heptane and/or toluene. Component b), preferably an organometallic compound from group 3 of the Periodic Table of the Elements, such as tri-C1-C10-alkylaluminum compounds, especially trimethylaluminum, or an aluminoxane, as defined above, preferably methylaluminoxane, is added to the suspension. Component b) can also be present as a solution, preferably in inert organic solvents, such as aliphatic, isocyclic hydrocarbons or aromatic hydrocarbons, ie. n-hexane, n-heptane, isododecane, toluene or ethylbenzene. The temperatures for this reaction are not critical. Components a), b) and c) are usually reacted at from xe2x88x9270 to 120xc2x0 C., preferably from 0 to 50xc2x0 C. After this impregnation process, it is common to remove virtually all of the solvent and to dry any solid which remains, preferably at from 20 to 120xc2x0 C., in particular at from 40 to 80xc2x0 C. The drying period is generally not critical and as a rule is in the range from 0.1 to 24 hours, depending on batch size.
The solid obtainable in this way is then usually mixed with a solution of the metallocene, preferably of the biscyclopentadienyl compounds Ib, Ic as defined above, especially bis(n-butylcyclopentadienyl)zirconium dichloride, bis(isobutylcyclopentadienyl)zirconium dichloride, dimethylsilanediylbis(indenyl)zirconium dichloride, dimethylsilanediylbis(2-methylbenzoinindenyl)zirconium dichloride, and with the metallocenium-forming compound, preferably methylaluminoxane. Subsequently, the solvent c) is normally removed almost completely, the solid which remains is dried, preferably at from 20 to 120xc2x0 C., in particular from 40 to 80xc2x0 C., and a defined amount of component c) is added (variant A) or else the amount of component c) in the novel solid can be established at the desired level by incomplete removal of component c) (variant B). The liquid c) added in variant A can, but need not, be chemically identical to the liquid c) originally present in the mixture.
The solid catalysts obtainable in this way are highly suitable for polymerizing C2-C12-alk-1-enes at from xe2x88x9250 to 300xc2x0 C. under pressures in the range from 0.5 to 5000 bar.
Of the C2-C12-alk-1-enes, preference is given to ethylene, propene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene and to mixtures of these C2-C12-alk-1-enes. Particular preference is given to homo- or copolymers of propene, the proportion of propene in the copolymers being at least 50 mol-%. Of the propene copolymers, those which are preferred include ethylene or 1-butene or mixtures thereof as additional monomers. Preferred ethylene polymers are copolymers with a proportion of from 50 to 99.9 mol-% of ethylene and from 0.1 to 50 mol-% of a C3-C10-alk-1-ene such as propene, 1-butene, 1-hexene, 1-octene, 1-decene or a mixture of these C3-C10-alk-1-enes, the proportions in the mixture not being critical.
The process for preparing polymers is usually conducted at from xe2x88x9250 to 300xc2x0 C., preferably at from 0 to 150xc2x0 C., and at pressures in the range from 0.5 to 5000 bar, preferably from 1 to 80 bar.
The polymerization can be accomplished in solution, in suspension, in liquid monomers or in the gas phase. Polymerization is preferably effected in liquid monomers, in suspension or in the gas phase, preference being given to the stirred gas phase or to the gas-phase fluidized-bed technique.
The process can be carried out continuously or batchwise. Suitable reactors include continuously operated stirred vessels or fluidized-bed reactors; alternatively, if desired, a row of series-connected reactors (reactor cascade) can be used.
The novel solid is notable for its lack of self-ignitability, which has been defined in accordance with the UN Recommendations Section 14.3 and EEC Directive 92/69, A 13. In accordance with these recommendations, the storage of small amounts of the novel solid in air is investigated. If it has not self-ignited within five minutes, it is classified as not self-igniting.
The novel solid, preferably consisting of components a), b) and c), can be used to dry fluids. Examples of these fluids are monomers, such as the above-defined C2-C2-12-alk-1-enes, for example ethylene, propylene, 1-butene and 1-hexene, and also organic solvents, such as those which constitute component c), examples being n-heptane and toluene. Gaseous fluids are the noble gases, preferably argon, and also nitrogen and gaseous hydrocarbons, for example propane and butane.

Abstract: a) at least one support component,

Abstract: c) at least one inert liquid and

Abstract: d) further components.


Methods and devices for optimized ridge near field apertures for thermally assisted magnetic recording are disclosed. The aperture dimensions and supporting dielectric materials are optimized for maximum energy absorption at the magnetic recording layer for a light source having a wavelength of 780 nm, which can be produced by low cost laser diodes.

1. Field of the Invention
This invention relates to devices for generating near-field light. More particularly, the present invention relates to methods and structures for generating optimized near-field light for thermally assisted magnetic recording.
2. Description of the Related Art
Near-field light sources are useful for generating subwavelength, intense light for use in optical microscopes, optical measurement instruments, spectroscopic instruments, optical recording and optical reproduction equipment, lithography equipment, and for thermally assisted magnetic recording. In the latter application, heat is applied to a magnetic substrate via a very small, but intense light source to reduce the anisotropy of fine grain magnetic structures. These fine grain structures are capable of high recording densities, but have an anisotropy at room temperature that is too high for typical magnetic fields produced by conventional recording heads. Heating allows the media to be written with field strengths of conventional heads. Another potential advantage is that lower field strengths produced by heads having broader field dimensions may also be used, which relaxes the tight dimensional requirements of the magnetic source or write head. However, to be useful for high density recording, the light source utilized for heating must be on the order of 50 nm or less in diameter. This is far beyond the optical diffraction limit for conventional light sources such as solid state lasers.
One method that commonly used to produce such a near-field light source is the ridge aperture or "C" shaped aperture. The device consists of rectangular shaped aperture placed in an electrically conductive metal film, which is supported on a transparent substrate. The substrate is transparent to the wavelength of incident radiation, and covers the area of the aperture. Extending into the center portion of the aperture is an electrically conductive ridge, generally an extension of the surrounding metal film. Incident radiation, polarized in the direction parallel to the ridge produces a near-field light source which appears close to or at the end of the ridge, in the gap between the end of the ridge and the opposing boundary of the aperture. Numerous prior art references have described the formation of near field light sources using ridge apertures, many of which are summarized below. It is clear from these publications that intensity of the near field light source depends strongly on: (1) the particular dimensions of the aperture, which include the length and width of the outer boundary as well as the length and width of the ridge; (2) the thickness and composition of the metal film surrounding the aperture; and, (3) the frequency of light used to illuminate the aperture. For thermally assisted recording, heating of the recording media is of prime importance, so besides the variables cited above, the absorption characteristics of the media and location of the near-field light source above the media become additional parameters of importance. Most practitioners skilled in the art disclose information dealing with efficiency of the apertures, which is computed from the ratio of the light flux impinging on the entire aperture to the flux generated by the near-field source, with little regard to the impact of adsorption efficiency within the media being heated by the near-field source. Furthermore, since cost is always a concern in today's mass storage device technology, it would be useful to build a device to produce near-field light sources utilizing 780 nm wavelength light emitting diode light sources, which are low cost devices.
What is needed is a device for producing near field light sources for use in thermally assisted magnetic recording applications, optimized for low cost 780 nm wavelength illumination light sources, that is also optimized for maximum adsorption efficiency by the recording media.
Sendur et al., in an article entitled "Ridge waveguide as a near-field aperture for high density data storage", Journal of Applied Physics, Volume 96, No. 5, September 2004, discloses the performance of the ridge waveguide as a near-field aperture in data storage systems. Finite element method (FEM) and finite-difference time-domain (FDTD) based software are used in the numerical simulations. To verify accuracy at optical frequencies, the FEM and FDTD are first compared to analytical results. The accuracy of these techniques for modeling ridge waveguides at optical frequencies is also evaluated by comparing results with plane wave illumination. The FEM, which is capable of modeling focused beams, is then used to simulate various geometries involving ridge waveguides. Near-field radiation from ridge waveguide transducer is expressed in terms of power density quantities. Previous studies in the literature consider the performance of the transducer in free space, rather than in the presence of a recording magnetic medium. The effect of the recording magnetic medium on the transmission efficiency and spot size is discussed using numerical simulations. The effect of various geometric parameters on the optical spot size and transmission efficiency is investigated and discussed. Based on our numerical simulations, a promising transducer design is suggested to obtain intense optical spots well below the diffraction limit. Numerical simulations suggest that a full width at half maximum spot diameter of 31 nm in the recording magnetic medium can be obtained. The maximum value of the absorbed optical power density in the recording medium is about 1.67×10−4 mW/nm3 for a 100 mW input power. This adsorbed power density is reported for a wavelength of 516 nm and silver conductive films. In-track and cross-track profiles for this design are compared with Gaussian distributions.
Batra et al., in an article entitled "Topology Visualization of the Optical Power Flow through a Novel C-Shaped Nano-Aperture", published in IEEE Visualization 2004, discloses a study describing the application of flow topology visualization techniques to the investigation of optical transmission through a novel C-shaped metal nano-aperture. This feature based vector field visualization technique can be extended generally to the flourishing field of Finite-Difference-Time-Domain (FDTD) methods used in many nano-photonics problems. Because of the diverse applications of the FDTD method and the vast amount of information it produces, an effective high-level abstraction of the data set can not only provide critical insight into the physical phenomena, it will also help direct ongoing research efforts. Recently discovered C-shaped sub-wavelength (nano) metallic apertures, when irradiated at specific resonance frequencies, have extraordinary power transmission five to six orders of magnitude beyond what is observed for conventional round or square apertures. These apertures produce optical spot sizes as small as 25-50 nm using visible light in the near-field of the aperture with a brightness 10-100 times higher than that of the illuminating beam.
Shi et al., in an article titled "Design of a C Aperture to Achieve λ/10 Resolution and Resonant Transmission", published in J. Opt. Soc. Am. B, vol. 21, No. 7, July 2004, discloses small subwavelength apertures providing high spatial resolution that is not limited by the diffraction limit. However, application of these apertures to practical problems has been hindered by the critical problem of extremely low power transmission efficiency. A well-designed C aperture can provide both a high spatial resolution of λ/10 and a high power throughput greater than 1. The authors present the underlying design ideas of the C aperture and report interesting general properties of optical transmissions through a single two-dimensional subwavelength aperture, based on numerical finite-difference time-domain simulations and fundamental observations. These results are expected to provide helpful information for both C aperture applications and general studies of subwavelength metallic structures.
Shi et al., in an article entitled "Ultrahigh Light Transmission Through a C-shaped Nanoaperture", published in Optics Letters, Vol. 28, No. 15, Aug. 1, 2003, discloses that optical resolution beyond the diffraction limit can be achieved by use of a metallic nanoaperture in a near-field optical system. Conventional nanoapertures have very low power throughput. Using a numerical finite-difference time domain method, the authors discovered a unique C-shaped aperture that provides ˜3 orders of magnitude more power throughput than a conventional square aperture with a similar near-field spot size of ˜λ/10. Microwave experiments at 6 GHz quantitatively confirmed the simulated transmission enhancement. The high transmission of the C-aperture, or one of the related shapes, is linked to both a propagation mode in the aperture and local surface plasmons.
Shi et al., in an article entitled "Mechanisms for Enhancing Power Throughput from Planar Nano-Apertures for Near-Field Optical Data Storage", published in J. Appl. Phys., Vol 41(2002), pp 1632-1635, discloses that near field optical data storage systems are important for ultrahigh density data storage. One type of near field optical data storage system uses a planar nanoaperture to define the data storage resolution. However, conventional nano-apertures have a tradeoff between resolution and power throughput. A "C" aperture design has been recently reported to overcome this problem. A study on the mechanisms for power throughput enhancement, based on a detailed study of nanoslits using numerical simulations is presented. Generating a propagation mode is essential for high power throughput, and by optimizing the design of the aperture thickness, resonant transmission can be achieved for even higher power throughput.
Matteo et al., in an article entitled "Fractal extensions of near-field aperture shapes for enhanced transmission and resolution", published in Optics Express, Vol. 13, No. 2, Jan. 24, 2005, discloses families of fractals investigated as near-field aperture shapes. They are shown to have multiple transmission resonances associated with their multiple length scales. The higher iterations exhibit enhanced transmission, and spatial resolution exceeding the first order. Near-field enhancements of greater than 400 times the incident intensity and resolutions of better than λ/20 have been shown with apertures modeled after third iteration prefractals. Enhancements as large as 1011 have been shown, when compared with conventional square apertures that produce the same spot size. The effects of the complex permittivity values of the metal film are also addressed.
Matteo et al., in an article entitled "Spectral analysis of strongly enhanced visible light transmission through single C-shaped nanoapertures", published in App. Phys. Letters, Vol. 35, No. 4, Jul. 26, 2004, discloses single C-shaped apertures designed, fabricated, and characterized in an Au film, resonant in the visible regime. The C-shaped apertures showed transmission enhancement of 13-22 times over a square aperture of the same area and suggest as high as 106 times enhancement over square apertures that are designed to produce the same near-field spot size. Spectra from individual apertures demonstrate the ability to tune this resonance over 70 nm by scaling the dimensions of the apertures. This shows the C aperture to be a versatile tool for gaining high-resolution, enhanced transmission through single subwavelength apertures at optical wavelength.
Chen et al., in an article entitled "Imaging of optical field confinement in ridge wave guides fabricated on very-small-aperture laser", published in App. Phys. Letters, Vol. 83, No. 16, Oct. 20, 2003, discloses the optical field confinement in a ridge wave guide nano-structure ("C" aperture) designed for ultrahigh-density recording, observed using an apertureless near-field scanning optical microscope. The aperture was fabricated on a commercial edge-emitting semiconductor laser as the light source. High-contrast near-field images at both 1× and 2× lock-in detection frequencies were obtained. The emission patterns are in agreement with theoretical simulation of such structures. A 90 nm×70 nm full width half maximum spot size was measured and is comparable to the ridge width of the aperture.
Itagi et al., in an article entitled "Ridge waveguide as a near-field optical source", published in App. Phys. Letters, Vol. 83, No. 22, Dec. 1, 2003, discloses the feasibility of using a ridge waveguide at optical frequencies as a near-field optical transducer, using the finite difference time domain method. The complete electromagnetic field picture of the ridge waveguide, in the absence and presence of the irradiated medium, is presented. A power efficiency of 7% and an optical spot with full width half maximum of 50 nm×80 nm is obtained in the medium. We show that impedance considerations play a major role in the transducer-medium optical coupling.
U.S. Pat. No. 5,696,372 discloses a near-field electromagnetic probe that converts an incident energy beam into an interrogating beam which exhibits, in the near-field vicinity of the probe, a transverse dimension that is small in relation to the wavelength of the incident energy beam. The probe comprises an energy source for providing the incident energy beam with a wavelength λ. An antenna is positioned in the path of the incident energy beam and comprises at least a first conductive region and a second conductive region, both of which have output ends that are electrically separated by a gap whose lateral dimension is substantially less than λ. The electromagnetic system which produces the incident energy should preferably have its numerical aperture matched to the far-field beam pattern of the antenna. Further, the incident beam should have a direction of polarization which matches the preferred polarization of the antenna. The near-field probe system of the invention can also sense fields in the near-field gap and reradiate these to a far-field optical detector. Thus the probe can serve to both illuminate a sample in the near-field gap, and to collect optical signals from an illuminated sample in the near-field gap.
U.S. Pat. No. 6,649,894 discloses an optical near-field probe of high resolution and high efficiency. A near-field light is generated using a tapered, plane scatterer formed on a substrate surface. The intensity of the near-field light is enhanced by making the area of the scatterer smaller than that of a light spot and by selecting the material, shape, and size of the scatterer so as to generate plasmon resonance. An optical near-field generator having a high light utilization efficiency can be obtained.
U.S. Pat. No. 6,714,370 discloses a recording head for use in conjunction with a magnetic storage medium, comprising a waveguide for providing a path for transmitting radiant energy, a near-field coupling structure positioned in the waveguide and including a plurality of arms, each having a planar section and a bent section, wherein the planar sections are substantially parallel to a surface of the magnetic storage medium, and the bent sections extend toward the magnetic storage medium and are separated to form a gap adjacent to an air bearing surface, and applies a magnetic write field to sections of the magnetic recording medium heated by the radiant energy. A disc drive including the recording head and a method of recording data using the recording head are also provided.
U.S. Pat. No. 6,768,556 discloses a near-field probe including a metallic scatterer fabricated on a substrate in a contour of a circular cone, a polygonal pyramid, a planar ellipse, or a triangle and a film of a metal, a dielectric, or a semiconductor formed in a periphery of the scatterer with film thickness equal to height of the scatterer.
U.S. Pat. No. 6,785,445 discloses a near-field light probe capable of emanating a near-field light having a sufficient intensity while allowing reduction of aperture size to improve resolution. The near-field light probe can be incorporated in a near-field optical microscope, a near-field light lithography apparatus, and a near-field light storage apparatus. A near-field light probe has a configuration in which a light-blocking film is formed with an aperture having slits surrounding the major opening. Light emitted from a light source is coupled into the probe from one side of the light-blocking film, the light being polarized in a predetermined direction with respect to the slits so that a near-field light emanates from the major opening.
U.S. Pat. No. 6,795,380 discloses a pair of members opposed to each other via a gap which are commonly used as an evanescent light probe and a writing magnetic head. When the spacing and width of the gap are smaller than the wavelength λ of injected light, highly intensive evanescent light is generated from the gap position of the opposite surface. Magnetic writing is carried out by applying a recording magnetic field from the pair of members to a medium heated by the evanescent light.
U.S. Pat. No. 6,839,191 discloses an optical near-field generating element provided with: a light shielding member, which is placed on an optical path of light emitted from a light source, for defining a micro opening having a diameter equal to or shorter than a wavelength of the light; and a dielectric film placed in close contact with the micro opening. Alternatively, an optical near-field generating element is provided with a light shielding member, which is placed on an optical path of lights emitted from a light source, for defining a micro opening having a diameter equal to or shorter than a wavelength of the light, the shielding member equipped with: a main portion for defining a basic shape of the micro opening; and a protrusion portion protruding from the main portion toward the center of the micro opening.
US Patent Application Publication 2003/0015651 discloses optical apparatuses using the near-field light where high spatial resolution and high sensitivity are made compatible. Highly intense near-field light is generated in a narrow area using localized plasmons that are produced in a metal pattern in the shape that bears anisotropy and is made to irradiate a measured subject. The direction of polarization of incident light is modulated and signal light is subjected to synchronous detection, so that background light is removed and high sensitivity is achieved.
US Patent Application Publication 2003/0184903 discloses a ridge wave guide having a recessed ridge forming an isolated tip at a terminal end of the wave guide's aperture which efficiently couples light into a spot adjacent to the tip in a medium below the terminal end of the wave guide that is significantly smaller than the light's wavelength. The wave guide is used to heat a recording medium via the small spot for heat assisted recording or to pattern substrates by photolithography with line width exposures that are significantly smaller than the wavelength of light. The body of the wave guide may also be recessed away from the medium in an area surrounding the wave guide's aperture to further confine the energy emerging from the wave guide to the small spot adjacent the tip in the medium.
US Patent Application Publication 2003/0223316 discloses a recording head for decreasing recording noise accompanying malformation of a recorded mark and the formation of a recorded mark capable of increasing reproduction resolution at the time of magnetic reproduction. The head has a light source and a scatterer for recording information on a recording medium by generating near-field light by application of light from the light source and forming a magnetic domain array on the recording medium, a perimeter of the scatterer defines a plurality of vertices and a distance between a first vertex and a last vertex is shorter than the width of the recording track on the recording medium. The recording head improves recording density and can be used to manufacture a highly reliable information recording and reproducing apparatus having a reduced cost per capacity.
US Patent Application Publication 2004/0062152 discloses a device for writing data to a recording medium and a method for fabricating the device. According to one embodiment, the device includes an electrical conductor having a cross-track portion, wherein the cross-track portion includes first and second opposing surfaces, and wherein the cross-track portion defines an aperture extending from the first surface to the second surface. The device also includes a dielectric portion disposed in the aperture such that the dielectric portion defines a ridge waveguide having a lowest-order mode cut-off frequency that is less than the frequency of incident optical energy used to heat the recording medium.
US Patent Application Publication 2005/0031278 discloses near-field sub-wavelength C-apertures that provide enhanced spatial resolution and power throughput by increasing the normalized resonant wavelength of the aperture. These improved apertures are characterized by the use of improved geometric proportions for C-apertures, filling the aperture with high-index material, designing aperture thickness to produce longitudinal transmission resonance, and/or tapering the aperture in the longitudinal direction to achieve impedance matching. Apertures according to the present invention may be used for many technological applications in various portions of the electromagnetic spectrum. Exemplary applications to high density optical data storage and optical particle trapping and manipulation are described.
US Patent Application Publications 2005/0030992 and 2005/0030993 disclose a near field optical apparatus comprising a conductive sheet or plane having an aperture therein with the conductive plane including at least one protrusion which extends into the aperture. The location, structure and configuration of the protrusion or protrusions can be controlled to provide desired near field localization of optical power output associated with the aperture. Preferably, the location, structure and configuration of the protrusion are tailored to maximize near field localization at generally the center of the aperture. The aperture preferably has a perimeter dimension which is substantially resonant with the output wavelength of the light source, or is otherwise able to support a standing wave of significant amplitude. The apparatus may be embodied in a vertical cavity surface emitting layer or VCSEL having enhanced nearfield brightness by providing a conductive layer on the laser emission facet, with, a protrusion of the conductive layer extending into an aperture in the emission facet. The aperture in the emission facet preferably has dimensions smaller than the guide mode of the laser, and the aperture preferably defines different regions of reflectivity under the emission facet. The depth of the aperture can be etched to provide a particular target loss, and results in higher optical power extraction from the emission facet.
International Publication WO 01/17079 discloses a near-field optical apparatus comprising a conductive sheet or plane having an aperture therein, with the conductive plane including at least one protrusion which extends into the aperture. The location, structure and configuration of the protrusion or protrusions can be controlled to provide desired near-field localization of optical power output associated with the aperture. Preferably, the location, structure and configuration of the protrusion are tailored to maximize near-field localization at generally the center of the aperture. The aperture preferably has a perimeter dimension which is substantially resonant with the output wavelength of the light source, or is otherwise able to support a standing wave of significant amplitude. The apparatus may be embodied in a vertical cavity surface emitting layer or VCSEL having enhanced near-field brightness by providing a conductive layer on the laser emission facet, with a protrusion of the conductive layer extending into an aperture in the emission facet. The aperture in the emission facet preferably has dimensions smaller than the guide mode of the laser, and the aperture preferably defines different regions of reflectivity under the emission facet. The depth of the aperture can be etched to provide a particular target loss, and results in higher optical power extraction from the emission facet.

Optimized ridge apertures for thermally assisted magnetic recording

Hitachi Global Storage Technologies Netherlands B.V.


Paper is made by mixing anionic starch, carboxyl methyl cellulose or other polymeric binder into a cellulosic thin stock together with a cationic inorganic or polymeric coagulant and then flocculating the suspension by means of an anionic swelling clay or other anionic retention aid.

This invention relates to processes for making paper (by which we include paper board), and in particular processes of making paper which is strengthened by starch.
It is standard practice to make paper by a process comprising flocculating a cellulosic suspension by the addition of a high molecular weight, polymeric, retention aid, draining the flocculated suspension through a wire to form a wet sheet, and drying the sheet.
One particular class of paper-making processes are microparticulate processes in which the flocculation with polymeric retention aid is followed by degrading the flocs by agitation and then reflocculating by the addition of a microparticulate material, such as bentonite.
It is well known to include low molecular weight cationic polymer in the suspension, either by addition at the thick stock stage or subsequently, in various paper-making processes for various purposes. It is also well known to include inorganic coagulants such as poly aluminium chloride or alum for various purposes. Reference is made to, for instance, U.S. Pat. No. 4,913,775 for a description of various processes and, in particular, a microparticulate process sold under the trade name Hydrocol.
It is known to add cationic starch to the cellulosic suspension in papermaking processes as a strengthening aid, and in some processes it also contributes to retention. Processes have also been described which comprise addition of raw, untreated starch to the cellulosic suspension. Processes in which starch is added to the cellulosic suspension generally tend to have the disadvantage that particular care must be taken to ensure good retention of starch so that there are not significant levels of dissolved or undissolved starch in the whitewater draining through the wire. See for instance WO95/33096.
Processes are described in GB 2,292,394 in which anionic starch, carboxy methyl cellulose or other polymeric binder capable of hydrogen bonding to cellulose are added to the thin stock with a cationic polymer which has a molecular weight above 150,000, preferably 1 million or more and which insolubilises the anionic binder. Cationic starch can also be added.
Processes are described in WO93/01353 in which an anionic retention aid based on starch, a cellulosic derivative or guar gum free of cationic groups and an aluminium compound are added to the suspension. Another disclosure of processes in which an anionic compound and a low molecular weight cationic polymer are added to the suspension is in JP-A-03193996.
Although various processes which are known can be optimised to give useful strength in the dry sheet and can be optimised to give satisfactory short drainage times and/or good retention of the fibres and/or the binder, it would be desirable to be able to provide a process which gives optimum utilisation of the binder in the sheet (and thus optimum strength) together with good retention of the binder, the fibres and the fines in the cellulosic suspension, and good drainage properties.
It might have been thought that these objectives could be achieved by modifying the process described in GB 2,292,394 by adding a high molecular weight cationic polymeric retention aid to the suspension, but we have found that this does not give any significant or useful improvement.
According to the invention, a process for making paper (including paper board) comprises providing a thin stock suspension of cellulosic fibres, mixing into this suspension (a) a water soluble anionic or non-ionic polymeric binder and (b) a water soluble cationic material selected from water soluble organic polymeric coagulants having intrinsic viscosity not more than 3 dl/g and inorganic coagulants,
then flocculating the suspension by mixing into the suspension an anionic retention aid (which may be a microparticulate anionic retention aid),
draining the flocculated suspension to form a wet sheet, and
drying the wet sheet.
We have surprisingly found that the addition of the anionic retention aid, instead of traditional cationic polymeric flocculants, after addition of the binder and cationic polymeric coagulant, gives good flocculation of the suspension and subsequently a marked improvement in the drainage rate and good retention of fibre and fines. Further, it does not lead to any significant deterioration in the retention of binder and so gives good retention of the binder.
The cellulosic suspension may be any conventional thin stock formed from any conventional cellulosic feed, including recycled feed material. The thin stock may be substantially unfilled (i.e., without the deliberate addition of significant amounts of filler) or it may be filled.
The binder is a water soluble material capable of substantial hydrogen bonding with cellulose. That is, it is capable of binding with the cellulose fibres in the paper stock, for instance to levels of at least 1 or 2% (dry binder based on dry stock), often with a binder retention of at least about 60 or 70 or even 80%. In practice the binder needs to be non-ionic or anionic, since if it is cationic then the binding of the binder to the cellulosic fibres will predominantly be due to the cationic groups rather than due to hydrogen bonding. In order that hydrogen bonding predominates, the non-ionic or anionic binder will normally be a polyhydroxy material. In order that it acts as a binder in the final sheet, thereby increasing the strength of the sheet, it must be polymeric and of high molecular weight. Thus the molecular weight will normally be in excess of 5,000, and often in excess of 50,000 and generally above 100,000.
In practice, the polymeric binder is usually a cellulosic compound, a natural gum or a starch, but it can be a synthetic polymer such as polyvinyl alcohol. Natural and modified natural polymers include cellulosics, gums and starches, for instance carboxymethyl cellulose, xanthan gum, guar gum, mannogalactans and, preferably, anionic starch. The binder preferably has a pendant ionisable group which is generally sulphate, carboxylate or phosphate. Suitable starches include oxidised starch, phosphate starch and carboxy methylated starch.
The amount of binder is normally at least about 1% (dry weight binder based on dry weight suspension) and can be up to, for instance, 10%. Generally it is 1 to 8%, preferably around 3%, for instance 3 to 5% (i.e., 30 to 50 kg/t).
The cationic material is preferably a cationic polymeric coagulant which has IV not more than 3 dl/g. In this specification IV is intrinsic viscosity measured by suspended level viscometer at 25xc2x0 C. in 1N sodium chloride buffered to pH 7. Preferably IV is not more than 2 dl/g, for instance 1.5 dl/g or below. Normally it is at least 0.1 or 0.5 dl/g. Preferred cationic polymeric coagulants have high charge density, for instance above 3 meq/g and usually above 4 meq/g.
Inorganic coagulant such as aluminium compounds, for instance poly aluminium chloride, can be used alone as the water soluble cationic material, or in combination with the polymeric coagulant.
The preferred cationic polymeric coagulants are materials such as polyethylene imines or polyamines (both preferably being fully quaternised), dicyandiamide condensation polymers (usually being substantially fully quaternised or in salt form) and polymers of water soluble ethylenically unsaturated monomer or monomer blend which is formed of 50 to 100 mole percent cationic monomer and 0 to 50 mole percent other monomer. The amount of cationic monomer is usually at least 80 to 90 mole percent, and homopolymers are often preferred. Ethylenically unsaturated cationic monomers that can be used include dialkylaminoalkyl (meth)-acrylates and -acrylamides (usually in quaternary or other salt form) and diallyl dialkyl ammonium chloride, for instance diallyl dimethyl ammonium chloride (DADMAC). Particularly preferred polymers are DADMAC homopolymers and copolymers.
When the polymer is a copolymer, the comonomer is usually acrylamide, or other water soluble non-ionic ethylenically unsaturated monomer.
The cationic polymeric coagulant may be a linear polymer. Alternatively it may be produced in the presence of multifunctional additives which produce structure, for instance polyethylenically unsaturated monomers such as tetraallyl ammonium chloride, methylene bis acrylamide and multifunctional monomer included in the polymer chain. The amount of these additives, if used, is generally at least 10 ppm and usually at least 50 ppm. It may be up to 200 or 500 ppm.
The amount of cationic material is normally an excess over that amount which is required to give observable retention when the anionic retention aid is added. The amount may be sufficient to cause the suspension to have a zeta potential which is around zero or is positive, but satisfactory retention is often obtainable even though the zeta potential is slightly negative. In practice, the amount of cationic material is best determined by forming a thin stock containing the desired amount of the binder (having regard to the strength properties that are required) and then observing the retention effect upon adding the retention aid after adding various amounts of the cationic material.
It is usually undesirable for the cationic material to include any significant amount, or indeed any amount, of high molecular weight cationic polymeric material (for instance intrinsic viscosity above 4 dl/g) since the use of such a material does not usually cause any improvement in performance, provided sufficient cationic material which is inorganic and/or low molecular weight has been used. However, if desired, other materials can be added with or after the cationic polymeric or inorganic coagulants discussed above, provided these extra materials do not interfere with the process.
The amount of cationic polymeric coagulant is normally from 0.25 to 10 kg active polymer per ton dry cellulosic suspension, preferably 1 to 3 kg/t.
In the process the binder may be added prior to the cationic coagulant or after the cationic coagulant. The binder and coagulant may be added essentially simultaneously. The coagulant may be added as a single dose or as a split dose, for instance partially before and partially after the binder. The order of addition of the binder and cationic coagulant can be varied as convenient without significant deterioration in results.
After treatment of the suspension with the binder and cationic polymeric coagulant, the anionic retention aid is mixed into the treated suspension. This mixing may be done under medium or high shear, but is normally done under sufficient force simply to mix the anionic retention aid into the suspension, for instance at the headbox or prior to it.
The amount of anionic retention aid is normally 0.5 to 10 kg/t dry cellulosic suspension, preferably 1 to 4 kg/t.
The anionic retention aid is a material which acts to flocculate the treated thinstock suspension and thus improve the drainage in comparison with a non-flocculated treated thinstock suspension.
It may be a substantially water soluble anionic polymeric material and thus it may be, for instance, a material as described in WO98/29604.
Preferably, however, it is a microparticulate anionic retention aid which may be inorganic or organic. For instance, it may be an organic anionic microparticulate retention aid such as described in U.S. Pat. Nos. 5,167,766 and 5,274,055. Preferably it is an inorganic anionic microparticulate retention aid. Such materials are well known and include swelling clays, generally referred to as bentonite, colloidal silica, polysilicic acid, polysilicic acid or polysilicate microgels, and aluminium modified versions of these. Mixtures may be used, e.g., of organic and inorganic microparticles.
Preferably no additional components are added to the cellulosic suspension after treatment with binder and cationic coagulant and before addition of anionic retention aid.
After treatment with the anionic retention aid the flocculated suspension is drained through a wire to form a wet sheet. The wet sheet is then dried in standard manner to form a dry paper (including paper board) sheet.
In the process the retention of binder in the sheet is preferably at least 60 or 70%, more preferably at least 80%, and even 85 or 90% or above.
In the invention we also provide the use of an anionic retention aid as discussed above to improve the drainage of a cellulosic suspension which has been treated with binder and cationic polymeric coagulant, of the types discussed above.
In the process we often find that drainage times for a given volume of backwater can be reduced to 70 or 60% of drainage times under equivalent conditions but without addition of anionic retention aid, and may even be reduced to below 50 or 40% of these times.

Ciba Specialty Chemicals Water Treatments Ltd.


A method of intelligently copying recovery points from a primary storage device to a secondary storage device is presented. The decision on how to copy the recovery points depends upon the backup copy policy as well as the availability of previous backups on the secondary storage device.

1. Field of the Invention
The present invention relates to computer system backup. More particularly, the present invention relates to a system and method of copying recovery points from one storage system to another.
2. Description of the Related Art
A backup refers to the making of copies of managed data so that the copies can be used to restore the managed data in the event that the managed data is lost. Typically, the managed data is stored in original storage, a primary copy of the managed data is stored in primary storage and a secondary copy of the managed data is stored in secondary storage. For example, the managed data is stored in a client system, the primary copy of the managed data is stored in a media server, and the secondary copy of the managed data is stored in a magnetic tape device.
The primary copy of the managed data stored in primary storage is organized to allow the managed data to be quickly and easily restored. For example, initially and then periodically, a full backup of all of the managed data is taken. After that, an incremental backup of only the managed data that has changed since the previous full or incremental backup is taken.
A recovery point is the state of the managed data at a particular point in time. Stated another way, the recovery point is the managed data existing at a particular point in time that is being protected. Typically, a recovery point is a full backup or a full backup plus incremental backup(s).
Many backup products copy every full and incremental backup from primary storage to secondary storage. As a result, the entire chain of incremental backups is copied.
As a result, in the event that a recovery point must be restored, there is slow restore performance due to the long chain of incremental backups that must be used.
Further, often only particular recovery points of all of the recovery points in primary storage are desired to be copied to secondary storage. Thus, copying the entire chain of incremental backups to secondary storage results in more recovery points being copied to secondary storage than are desired.
Further, if any ancestor full backup or ancestor incremental backup is missing, it may not be possible to restore the recovery point.

Intelligent recovery point copying system and method


The invention relates to an intervertebral implant comprising a spacer (2) in which two opposite notches (6a, 6b) are formed suitable for receiving two respective spinus processes (26a, 26b) of two vertebrae, each notch defining two flanges (8a, 10a, 8b, 10b) each having an inside wall, and the implant also having a tie (4a, 4b) for holding said spacer on said spinus processes. Said tie is constituted by at least one strap having a portion surrounding a portion of the surface of a spinus process that is opposite from the bottom of the notch. Said implant has first fixing means (12a, 12b) formed in at least one flange (8a, 8b) for fixing a first end (18a, 18b) of said strap, and self-locking second fixing means (14a, 16a, 14b, 16b) formed in at least one other flange (10a, 10b) and through which the second end (20a, 20b) of said strap is inserted and then pulled to hold said strap (4a, 4b) in position, thereby securing said spacer (2) to said spinus processes (26a, 26b).

The present invention relates to an intervertebral implant comprising a spacer and a tie for holding the spacer between two vertebrae.
The spacer compensates for a vertebral disk when the disk is deficient and in particular it limits the extent to which the posterior portions of two vertebrae can move towards each other when the spine is extended. The posterior portions of two vertebrae coming too close together gives rise to discomfort, and in particular to pain.
When a vertebral disk has degenerated, movements of the spine can cause contact to be made between vertebrae which can pinch the roots of the nerves that come out laterally between the vertebrae.
To remedy that drawback, it is known to fix at least one spacer between two spinus processes of two consecutive vertebrae. These spinus processes project from the vertebrae in the form of knobbles on the posterior portion of the vertebral column.
Thus, by putting a spacer between two successive spinus processes, the vertebrae are prevented from coming into contact when the vertebral disk is deficient.
However, the spacer must be fixed to the vertebrae in a manner that is sufficiently rigid to keep it in position regardless of the movements of the spine, and it must be sufficiently free relative to the same vertebrae to avoid excessively stiffening the vertebral column. It is known to fix such a spacer, which has one or more through holes formed therein, by means of ligaments inserted in the holes and forming loops into which the spinus processes are engaged. That fixing system is not very rigid and it requires a large number of manipulations, thereby correspondingly increasing the time required for surgery.
An object of the present invention is to provide an intervertebral implant whose means for fixing to the spinus processes are capable of being put into place in a length of time that is relatively short compared with the prior art, and which provides fixing that is more rigid.
To achieve this object, the invention provides an intervertebral implant comprising a spacer in which two opposite notches are formed suitable for receiving the two spinus processes of two vertebrae, each notch defining two flanges each having an inside wall, the implant also having a tie for holding said spacer to said spinus processes, and the implant being characterized in that:
said tie is constituted by at least one strap having a portion surrounding a portion of the surface of the spinus process opposite from the bottom of the notch;
and in that said implant further comprises:
first fixing means formed in at least one flange to fix a first end of said strap; and
self-locking second fixing means formed in at least one other flange, the second end of said strap being inserted through said self-locking fixing means and then pulled to hold said strap in position, thereby securing said spacer to said spinus processes.
It will be understood that the spacer is inserted between two vertebrae and that each of the spinus processes extending therefrom bears against a respective opposite notch in said spacer. The various flexions of the spine give rise to each spinus process having a certain amount of mobility relative to the other, and the spacer is held in position by a strap which provides a contact area with the spinus process that is greater than that provided by a tie of the ligament type.
Consequently, the tie is held more securely to the spinus process. Furthermore, one end of the strap is fixed in one of the two flanges constituting the notch and advantageously the first fixing means comprise a slot formed through said flange, said first end of said strap being suitable for being engaged in said slot in such a manner as to form a loop whereby said first end of said strap is secured to said flange. This method of fixing is relatively easy to install. Thus, the end of the strap is fixed to said spacer by ligating the tip of the strap to a portion of its end after it has passed through said slot and a loop has been formed. This operation is performed prior to installing the spacer between two vertebrae.
The second end of the strap is fixed to said other flange via the self-locking fixing means that preferably comprise a first slot and a second slot that are parallel to each other, said slots being formed through the other flange, said second slot being situated between said first slot and the bottom of the notch such that the portion of the strap which passes through the first slot and projects from said inside wall of said other flange is pressed against the portion of the strap which penetrates into the second slot, thereby enabling the end of said strap to be locked by friction.
Advantageously, said tie has two straps and thus each notch has first fixing means in one of its flanges and self-locking fixing means formed in its other flange so as to enable two straps to be fixed, each strap being suitable for passing round a respective one of the spinus processes, whereby said spinus processes are held independently of each other.
It will be understood that the straps are suitable for being premounted so as to form a loop on each notch. The tip of the second end of each strap is then engaged in each second slot via the inside wall of each of said other flanges and is reinserted into the notch via said first slot so as to project from the inside wall of the flange.
When the spacer is inserted between the vertebrae, the spinus processes pass through the loops and fixing is finished off by pulling on the tips of the straps so as to hold said spinus processes tightly in the notches.
It will also be understood that the self-locking means are used during the tightening operation. The more the strap is tightened on the spinus process, the longer the portion of strap projecting from the inside wall of the flange that is pressed against the portion of the strap which penetrates into the second slot. Thus, the two strap portions are pinched between the inside wall of the flange and the body of the spinus process, thereby preventing said end of the strap from moving relative to the flange.
In a first embodiment, the spacer is fixed in parallel on the spinus processes by means of two separate straps.
In a second embodiment, the spacer is fixed on the spinus processes by means of a single strap.


A method is provided of using biocompatible surface-active agents to impart improved characteristics to a surface contacting a gas-supersaturated fluid, advantageously by forming on the surface a coating including an adsorbed biocompatible surface-active agent promoting surface charge neutralization or surface energy reduction, and of providing a surface contacting a gas-supersaturated fluid, the surface having such improved characteristics.

The present invention relates generally to the coating of medical device surfaces contacting gas-enriched fluids, and more particularly, to the coating of medical device surfaces forming fluid conduits (e.g., catheters, infusion guidewires, tubing, capillaries and the like) to impart improved characteristics to the surfaces contacting oxygen-supersaturated fluids during delivery.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Adverse biological reactions, such as thrombosis, inflammation and infection, are thought to result from tissues and fluids contacting or otherwise interacting with the surfaces of medical devices. Thus, for many years, there has been significant interest on the part of physicians and the medical industry to develop, manufacture and use clinically medical devices that do not tend to promote adverse biological reactions.
As described in U.S. Pat. No. 5,928,916, for example, one approach used for minimizing adverse biological reactions has been to attach various biomolecules to the surfaces of medical devices. Numerous attachment methods, such as covalent attachment techniques and ionic attachment techniques, have been used or suggested. Such attachment methods may involve the use of coupling agents to attach biomolecules to surfaces.
Heparin is a type of biomolecule often coupled to surfaces. Surface heparinization is thought to improve the thromboresistance of biomaterials and inhibit blood coagulation. The ""916 patent describes, inter alia, some of the history of surface heparinization development and some of the methods for attaching heparin to surfaces. There are many approaches to binding heparin to biomaterial surfaces, and while methods of surface heparinization to minimize certain undesirable biological reactions are known, heparin continues to be of interest in the development of non-thrombogenic blood-contact biomaterial surfaces.
Certain aspects commensurate in scope with the disclosed embodiments are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
While biomolecules such as heparin have been used on surfaces to inhibit adverse biological reactions, one aspect of the present invention relates to methods using biomolecules to impart improved characteristics to medical device surfaces contacting gas-supersaturated fluids. More generally, one aspect of the present invention relates to methods using a biocompatible surface-active agent to impart improved characteristics to medical device surfaces contacting gas-supersaturated fluids, e.g., by forming reactive or non-reactive coatings on such surfaces. By way of example and without limitation, the biocompatible surface-active agent, either alone, or in combination with other such agents or other substances [e.g., undergoing surface adsorption with (e.g., in competition with or complexed with) such agents or such other substances], may be covalently or ionically bonded to a surface; immobilized thereupon; or otherwise adsorbed or deposited therewith to form such coatings. The improved characteristics may be imparted, for example, by placing one or more coatings (alone or in a multi-layered structure) on the fluid contacting surface (e.g., by dip-coating, by flushing a coating fluid from a pressurized source across the surface, etc.) for sufficient time for adsorption to occur.
The term xe2x80x9cbiocompatible surface-active agentxe2x80x9d appearing herein means a substance forming a reactive or non-reactive coating on a fluid-contacting surface. Examples of biocompatible surface-active agents which may be used according to certain aspects of this invention include, by way of example and without limitation, a negatively charged moiety; a positively charged moiety; both a negatively charged moiety and a positively charged moiety; any biocompatible molecular entity that mitigates a high surface energy of a gas-supersaturated fluid delivery path (e.g., by promoting charge neutralization or surface free energy reduction); a protein; a globular protein; a structural protein; a membrane protein; a cell attachment protein; a glycoprotein; dipalmitoyl phosphatidylcholine (DPPC); a DPPC derivative; phosphorylcholine (PC); a mucous agent; a glycolated mucin; a polysaccharide; a surfactant; a nonproteolytic surfactant; a biocompatible surfactant; a glycosaminoglycan (GAG); a quaternary ammonium salt; stearalkonium; tridodecylmethyl ammonium chloride (TDMAC); benzalkonium; a biomolecule; heparin; a heparin salt; a water-soluble heparin salt; a water-insoluble heparin salt; cetyl trimethyl ammonium bromide (CTAB); and polyvinylpyrrolidone (PVP). In general, as used in the specification and claims, the term xe2x80x9cbiomoleculexe2x80x9d means a material that is capable of engaging in a biological activity or that is capable of modulating a biological activity, either alone or in combination with different biomolecules, and combinations thereof. An example of a reactive coating including a biomolecule is a heparin coating. An example of a non-reactive coating is a PVP coating.
The term xe2x80x9cgas-supersaturated fluidxe2x80x9d appearing herein means a fluid in which the dissolved gas content would occupy a volume of between about 0.5 and about 3 times the volume of the solvent normalized to standard temperature and pressure. Examples of solvents which may be used include physiologic saline, lactated Ringer""s, and other aqueous physiologic solutions. For medical applications, particularly advantageous gas-supersaturated fluids include oxygen-supersaturated fluids, although fluids including dissolved gases other than oxygen also may be used.
Compared to the fluids typically used clinically today, gas-supersaturated fluids are gas-enriched fluids including increased amounts of a dissolved gas. It is thought that gas-supersaturated fluids are xe2x80x9cmetastablexe2x80x9d in that, as compared to clinically-used fluids, there is an increased potential for dissolved gas to come out of solution. For example, particles such as dust, debris, etc. generally do not affect the dissolved gas of clinically-used fluids as the gas remains in a dissolved state in the presence of such particles. However, with gas-supersaturated fluids, such particles may interefere with, disrupt, create or otherwise intereact with gas nuclei that seed bubble formation, growth or coalescence.
For example, one way of delivering gas-supersaturated fluids is via a glass capillary. However, borosilicate glasses contain negatively charged groups that impart a high surface energy to the surface contacting the gas-supersaturated fluid. It is thought that this high surface energy tends to attract and bind particles such as dust, debris, etc. that may promote bubble formation when gas-supersaturated fluids are passed through the capillary.
In applications where gas-supersaturated fluids are infused directly into a patient, and in applications where such fluids first are mixed with other fluids for such infusion, it is desirable to minimize, inhibit or eliminate physicochemical transitions (e.g., the emergence or growth of gas bubbles in the infused fluid) that might possibly result in undesirable physiologic responses by the patient. Such responses may be immediate or delayed, depending upon the circumstances involved in the physicochemical event(s) (e.g., the rate at which gas bubbles grow or coalesce). Accordingly, a simple and convenient way of minimizing, inhibiting, or eliminating undesirable physicochemical activity, particularly non-reactive physiochemical activity, associated with surfaces contacting gas-supersaturated fluids may be desirable.
The present invention may address one or more of the problems set forth above. Certain possible aspects of the present invention are set forth below as examples. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
The present invention may include within its scope methods including the step of using biocompatible surface-active agents to impart improved characteristics to a surface contacting a gas-supersaturated fluid. The present invention also may include, by way of example and without limitation, methods including the step of forming a coating on a surface contacting gas-supersaturated fluids to impart improved characteristics to the surface, the coating including a biocompatible surface-active agent; methods including the step of providing a surface contacting gas-supersaturated fluids including a biomolecule coating imparting improved characteristics to the surface for such contacting; and methods including the step of coating a surface with heparin to impart improved characteristics to the surface for contacting gas-supersaturated fluids.
As used in the specification and claims, the term xe2x80x9cmedical devicexe2x80x9d means a device including a surface contacting gas-supersaturated fluid in the course of its operation, which fluid is used in a patient diagnostic or therapeutic procedure. This definition includes within its scope both blood contact and non-blood contact surfaces. This definition also includes within its scope devices for intravascular use, such as catheters, guidewires, and the like which may be placed into blood vessels or the heart, or proximate the heart, the brain, or other organs or tissues, and other devices, such as oxygenators, pumps, sensors, tubing, accumulators, capillaries, etc., which may be used either alone or in combination with such devices, advantageously for diagnostic or therapeutic purposes.
The present invention may be susceptible to various modifications and alternative forms. Specific embodiments of the present invention are described herein in detail. It should be understood, however, that the description set forth herein of specific embodiments is not intended to limit the present invention to the particular forms disclosed. Rather, all modifications, alternatives, and equivalents falling within the spirit and scope of the invention as defined by the appended claims are intended to be covered.

Coating medical device surfaces for delivering gas-supersaturated fluids