A curable composition and method for making hollow shell molds, such as those employed to make hearing aids. The curable composition includes a (meth)acryl functionalized curable component, a cure system, a pigment composition, and a dispersion stabilizing additive. The pigment composition includes at least one pigment disbursed within the curable composition. The dispersion additive maintains the pigment in a disbursed form prior to cure. The dispersion additive includes an alkali metal cation and a reaction product.

The present invention relates to curable compositions which include a pigment disbursed therein and a dispersion stabilizing additive which maintains the pigment in a disbursed form prior to cure. In particular, the curable compositions of the present invention are radiation curable compositions which have particular application for use in hollow shell molds, such as those employed to make hearing aids.
Curable (meth)acryl functionalized compositions have been use for the manufacture of hollow molded articles, and in particular articles such as hearing aids. Such compositions are ordinarily radiation curable due to the manufacturing efficiencies and cost savings as compared to using heat to cure. Additionally, ultraviolet and/or visible light can be employed to concentrate or direct the curing energy at a particular portion of the curable composition and to ensure the proper irradiation.
For example, U.S. Pat. No. 5,763,503 to Cowperthwaite, discloses a method for making hollow shells, i.e. housings for in-ear hearing aids, using a radiation curable composition. This patent discloses the use of a hydroxyalkylmethacrylate-capped component, a difunctional, urethane methacrylate monomer, a minor amount of unreacted hydroxalkyl(C2-3) methacrylate monomer and a photoiniator. This composition is described as being pourable and contains a viscosity-increasing amount of viscosity-increasing solid other than a colorant. This patent focuses on controlling and adjusting the viscosity of the composition to achieve formulations which produce better hollow-shelled articles. The presence of viscosity-affecting ingredients, including pigments, is described as being carefully limited.
Other (meth)acrylate-based curable compositions have used a combination of uv curable components to achieve the desired cure properties. For example, Japanese Laid-Open Patent Publication Nos. 10-130601 and 10-130602 reportedly assigned to Nippon Kayakuco, Ltd., disclose uv curing adhesive compositions for use as protective coatings on optical discs which employ a uv curable ethylenically compound, such as a (meth)acrylate compound, a photoinitiator, an organic peroxide and an amino accelerator compound. Among the disclosed curable compounds are 2-hydroxyethyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate and phenyl oxyethyl (meth)acrylate. Another example of a uv curing (meth)acrylate-based composition is disclosed in U.S. Pat. No. 5,908,873, which contains an aliphatic urethane acrylate oligomer, a reactive (meth)acrylate monomer, a release agent and a photoinitiator. This composition is used to affix coated and inked optical fibers in a ribbon configuration.
Using colorants, such as dyes and pigments, in (meth)acryl functionalized curable compositions has been used for visual inspection purposes, as well as providing color to the cured product to meet the demands of the particular application. Many colorants do not stay suspended or uniformly distributed in curable resin compositions for long periods of times, such as when subjected to storage conditions. For this reason, mixing to disburse and/or uniformly distribute the colorants throughout the resin composition is generally required to obtain the desired color upon cure. This additional mixing step is undesirable in production processes because it is costly, can be technician sensitive and may require the use of the mixed composition within a relatively short time period.
Moreover, if mixing of the colorant into the curable composition immediately prior to use is required, uniform dispersion often does not occur due to agglomeration which forms during storage.
One particular commercial area where these problems exist is in the manufacturing and repair of custom hearing aids. In this industry, a variety of different types of flesh tones must be closely matched, typically using low concentrations of pigments which have been chosen to produce a variety of industry standard colors and which allow for tailoring of the curable composition to a particular person""s skin. For the most part, these pigments are insoluble particles which tend to fall out of dispersion as sediment, due to their density. Compositions used in molding hollow shell articles, such as hearing aids, generally require relatively low viscosities in order to easily dispense and process the compositions into the final molded article. Low viscosity materials further accelerate the sedimentation of conventional pigments, and in particular the more commonly heavy pigments such as TiO2 and Fe2O3.
Efforts to use various filler materials such as silica to provide thixotropic character to pigmented compositions useful in the production of hollow shell articles, such as hearing aids, has been largely unsuccessful due to the resulting surface blemishes and loss of other aesthetic features upon cure. Moreover, these filled compositions were not readily pourable due to the addition of the fillers, causing additional difficulties during manufacturing.
Thus, there is a need for a curable composition which can be effectively used to make cured articles, such as hearing aides and other hollow shell products, which can incorporate a variety of colorants, and in particular solid pigments, and which can be formulated into pourable and relatively low viscosity compositions which do not require substantial mixing prior to use in order to uniformly disburse the colorant therein. Moreover, there is a need for a (meth)acryl functionalized composition, which can cure by a variety of mechanisms, including electromagnetic radiation, and which can be molded into hearing aids and other high quality finished products having precise skin tone matches and coloring.
The present invention relates to curable compositions which include:
(a) a (meth)acryl functionalized curable component useful as a matrix,
(b) a cure system for said curable component;
(c) a pigment composition comprising of at least one pigment disbursed within said curable component; and
(d) an additive which comprises an alkali metal cation and the reaction product of:
(i) a polyfunctional isocyanate and a member selected from an hydroxy and an amine; or
(ii) a phosgene or phosgene derivative and a compound having 3 to 7 polyethylene glycol ether units terminated at one end with an ether group and the other end with a reactive functional group selected from an amine, an amide, a thiol and an alcohol; or
(iii) a monohydroxy compound, a diisocyanate and a polyamine.
In another aspect of the present invention, there is included a composition useful for the manufacture of hollow shells, such as hearing aids, which includes:
a. a photocurable aliphatic urethane-acrylate oligomer matrix composition having disbursed therein a pigment and a dispersion stabilizer, said stabilizer comprising an alkali metal salt and an additive which is the reaction product of:
(i) a polyfunctional isocyanate and a member selected from an hydroxy and an amine; or
(ii) a phosgene or phosgene derivative and a compound having 3 to 7 polyethylene glycol ether units terminated at one end with an ether group and the other end with a reactive functional group selected from an amine, an amide, a thiol and an alcohol; or
(iii) a monohydroxy compound, a diisocyanate and a polyamine; and
b. a photoiniator.
The curable compositions of the present invention provide the ability to make hollow shell articles, such as hearing aids, having a substantially uniform cross-sectional thickness. Such control is due to the unique curable compositions and the ability to control the radiation exposure used to cure the compositions. Pigments used in the present invention are present in amounts sufficient to produce the desired color of the final article, without interfering with the radiation curing or final properties of the cured polymer. Moreover, the dispersion stabilizing component eliminates the need for mixing just prior to use, and ensures the desired qualities of color, surface finish and overall aesthetics.
One particularly desirable set of compositions particularly useful for making hollow shells, such as hearing aids, includes: a (meth)acryl functionalized curable component, such as an aliphatic urethane-acrylate oligomer and/or a polyfunctional (meth)acrylate ester monomer such as a di-, tri- and tetra(ethylene glycol) di(meth)acrylate, used in amounts of about 46.0 to about 74.0% by weight; reactive diluents, such as tri(ethylene glycol) dimethacrylate, hydroxypropyl and hydroxyethyl methacrylate, used in amounts of about 9 to about 30% by weight; photoinitiators such as diphenyl (2,4,6-trimethylbenzol)phosphene oxide, 1,benzoyl cyclohexanol and bis(2,4,6-trimethylbenzoyl)phenyl phosphene oxide, used in amounts of about 0.2 to about 1.20% by weight; pigments, such as TiO2 and Fe2O3, used in amounts of about 0.6 to about 0.8% by weight; a dispersion stabilizer as described in component (d) above, in amounts of about 0.1 to about 1.0% by weight; and various wetting, defoaming and odor masking agents used in amounts of about 0.04 to about 1.20% by weight.
In another aspect of the invention, there is included a method of making hollow shells which includes the use of the aforementioned composition. The inventive method includes the steps of:
a. pouring into a mold cavity of a mold a photo-curable composition comprising a (meth)acryl functionalized curable matrix component, a photoinitiator, a pigment and a dispersion stabilizer for said pigments, said dispersion stabilizer comprising an alkali metal salt and an additive which is the reaction product of:
(i) a polyfunctional isocyanate and a member selected from an hydroxy and an amine; or
(ii) a phosgene or phosgene derivative and a compound having 3 to 7 polyethylene glycol ether units terminated at one end with an ether group and the other end with a reactive functional group selected from an amine, an amide, a thiol and an alcohol; or
(iii) a monohydroxy compound, a diisocyanate and a polyamine; and
b. exposing said composition to photo-radiation for time and intensity sufficient to cure said composition to a shell having a substantially uniform cross-sectional thickness.
(Meth)acryl functional components useful in the present invention can be selected from a wide variety of materials. Desirably, the (meth)acryl functionalized component includes a poly(meth)acryl functionalized compound which is capable of crosslinking during cure.
Such monomers may be chosen from any of those commonly used in the art. For example, useful monomers include, without limitation, those corresponding to the following general formula:
wherein R1 is selected from hydrogen, halogen, and lower alkyl of 1-4 carbon atoms; R2 is selected from the group consisting of hydrogen, xe2x80x94OH and
R3 is a radical selected from hydrogen, lower alkyl of 1-4 carbon atoms and hydroxyalkyl of 1-4 carbon atoms; and m is an integer equal to at least 1, desirably from 1-20 and more desirably from 1 to 4; n is an integer equal to at least 1, desirably 1 to 20; and p is 0 or 1.
Typical of these monomers are mono-, di-, tri- tetra- and polyethylene glycol di(meth)acrylate and the corresponding diacrylates; di(pentamethylene glycol) di(meth)acrylate; tetraethylene glycol di(chloroacrylate); diglycerol diacrylate; diglycerol tetra(meth)acrylate; butylene glycol di(meth)acrylate; neopentyl glycol diacrylate; and trimethylpropane triacrylate.
Particularly useful polymerizable crosslinkable components are ethoxylated trimethylolpropane triacrylate, trimethylol propane tri(meth)acrylate, dipentaerythritol monohydroxypentacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanedioldiacrylate, neopentyl glycoldiacrylate, pentaerythritol tetraacrylate, 1,2-butylene glycoldiacrylate, trimethylopropane ethoxylate tri(meth)acrylate, glycerol propoxylate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, tri(propylene glycol) di(meth)acrylate, neopentylglycol propoxylate di(meth)acrylate, 1,4-butanediol di(meth)acrylate, polyethyleneglycol di(meth)acrylate (PEGMA), triethyleneglycol di(meth)acrylate, butylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate and combinations thereof.
Other useful monomers include those acrylates derived from bisphenol-A, such as bisphenol-A di(meth)acrylate, hydrogenated bisphenol-A di(meth)acrylate, and ethoxylated bisphenol-A di(meth)acrylate (EBIPMA).
While di- and other polyacrylate esters are used for producing a cross-linked product, monofunctional acrylate esters (esters containing one acrylate group) also may be additionally incorporated. These materials are often incorporated as reactive diluents which are capable of copolymerizing with the various other polymerizable materials. When dealing with monofunctional acrylate esters, it is desirable to use an ester which has a relatively polar alcoholic moiety. Such materials are less volatile than low molecular weight alkyl esters and, more importantly, the polar group tends to provide intermolecular attraction during and after cure, thus producing more desirable cure properties, as well as a more durable sealant or adhesive. Particularly desirable are the polar groups selected from labile hydrogen, heterocyclic ring, hydroxy, amino, cyano, and halogen polar groups. Useful examples of compounds within this category include cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, hydroxyethyl acrylate, hydroxypropyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, cyanoethylacrylate, and chloroethyl (meth)acrylate. Other unsaturated reactive diluents, such as styrene and acrylonitrile, can also be used.
It is desirable that aromatic reactive diluents be incorporated into the composition. Useful aromatic-containing reactive diluents include, without limitation, those compounds corresponding to the structure:
wherein R5 may be H, CH3, CH2CH3; R6 may be (CH2)n, and n may be an integer from 1-4; R6 may also be substituted with xe2x80x94OH or halide when n is 2-4; and R7 may be a substituted or unsubstituted aromatic group such as phenyl, benzyl or a fused aromatic ring, such as napthalene, anthracene, and the like. R7 may also be an alkaryl, alkaryloxy or aryloxy group.
Urethane-acrylate curable oligomers are particularly useful in the present invention. For example, these materials can be described as the acrylated reaction product of an aliphatic alcohol, such as a polycarbonate polyol or a polyether polyol, and a polyisocyanate.
Representative polyether polyols useful in preparing the urethane-acrylate oligomers include straight or branched alkylene oxides having from one to twelve carbon atoms (C1-12), prepared by methods known in the art. Desirable, the polyether polyols have an average molecular weight, as determined by vapor pressure osmometry (ASTM-D 3592), sufficient to give the entire oligomer a molecular weight of about 6,000 daltons, desirably not more than 5,000 daltons and more desirably not more than 4,000 daltons. Examples include, without limitation; polytetramethylene polyol, polymethylene oxide, polyethylene oxide, polypropylene oxide, polybutylene oxide and combinations thereof.
Representative hydrocarbon polyols used to prepare the urethane-acrylate oligomers also include hydrocarbon polyols, straight or branched, having a molecular weight of from about 600 to 4,000. Non-limiting examples include fully or partially hydrogenated polybutadiene, polybutadiene hydrogenated to an iodine number of from 9 to 21, and fully or partially hydrogenated polyisobutylene.
Representative polycarbonate polyols used to prepare the urethane-acrylate oligomers include but are not limited to the reaction products of dialkyl carbonate with an alkylene diol, optionally copolymerized with alkylene ether diols.
The polyisocyanates used to prepare the urethane-acrylate oligomers include aliphatics and aromatics having from 4 to 20 carbon atoms (C4-20). Representative aliphatic examples include isophorone diisocyanate, dicyclohexylmethane-4,4xe2x80x2-diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylene diisocyanate, 1,9-nonamethylene diisocyanate, 1,10-decamethylene diisocyanate, 2,2,4-trimethyl-1,5-pentamethylene diisocyanate, 2,2xe2x80x2-dimethyl- 1,5-pentamethylene diisocyanate, 3-methoxy-1,6-hexamethylene diisocyanate, 3-butoxy-1,6-hexamethylene, omega, omegaxe2x80x2-dipropylether diisocyanate, 1,4-cyclohexyl diisocyanate, 4,3-cyclohexyl diisocyanate, trimethylhexylmethylene diisocyanate and combinations thereof.
Suitable catalysts for reacting the polyol with the polyisocyanate to form the urethane portion of the urethane-acrylate oligomers include such materials as: dibutyl tin dilaurate, dibutyl tin oxide, dibutyl tin di-2-hexoate, stannous oleate and octoate, lead octoate, ferrous acetoacetate; and amines, such as triethylamine, diethylmethylamine, triethylenediamine, dimethylethylamine, morpholine, N-ethyl morpholine, piperzine, N,N-dimethyl benzylamine, N,N-dimethyl laurylamine and combinations thereof.
The urethane oligomers thus formed are endcapped with a (meth)acrylate-containing group to form the urethane-acrylate. Suitable hydroxyl-terminated endcapping monomers include, without limitation, hydroxyalkyl (meth)acrylates, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and the like. Combinations of endcapping groups may be employed.
The molar ratio of the polyol, polysocyanate and endcapping monomer is desirably about 1:2:2, respectively.
Representative commercially available urethane-acrylate oligomers include: Photomer.RTM 6008 from Henkel Corporation, Ambler, Pa. which is an aliphatic urethane acrylate oligomer formed from polyether polyol, dicyclohexyl methane diisocyanate and hydroxyethyl acrylate. The oligomer has a number average molecular weight of about 1,500 daltons and is sold as a solution in tripropylene glycol diacrylate diluent: Photomer.RTM.6019, also from Henkel Corporation, analogous to the above, but based on isophorone diisocyanate rather than dicylohexyl methane diisocyanate; and Photomer.RTM.6010, also from Henkel Corporation, which is an aliphatic urethane-acrylate oligomer formed from polyether polyol, dicyclohexyl methane diisocyanate and hydroxyethyl acrylate in trimethylolpropane triethoxy triacrylate diluent. It has a number average molecular weight of about 1,500 daltons.
Other useful commercially available urethane-acrylate oligomers include Sartomer CN980, CN981, CN983 and Sartomer CN985, Sartomer Company, Exton, Pa.; and Echo Resins ALU-350 series, which are polytetramethylene polyol-based acrylated aliphatic urethane oligomers. Other useful oligimers are set forth in U.S. Pat. No. 5,908,873, which is incorporated therein by reference.
The (meth)acryl functionalized component of the present invention may be employed in amounts of about 30 to about 97%, desirably about 80 to about 97%, more desirably about 90 to about 97% and even more desirably in amounts of about 95 to about 97% by weight of the total composition.
In applications where hollow shells are to be made, the cure system is desirably one which is initiated by electromagnetic radiation. Photoradiation is most desirable for its ability to produce a well-controlled cure and high quality parts efficiently. Various photoinitiators, such as UV, visible and infrared may be employed.
Most desirably are the UV photoinitators. These photoiniators are generally effective in the 200 to 450 mm range, and particularly in the portion of the ultraviolet spectrum which borders on the invisible light and the visible portion just beyond this, e.g.  greater than 200 mm to about 390 mm.
A variety of UV photoinitiators may be employed. Photoinitiators, those that will respond to UV radiation to initiate and induce curing of the (meth)acryl functionalized curable component, which are useful in the present invention include benzophenone and substituted benzophenones, acetophenone and substituted acetophenones, benzoin and its alkyl esters, xanthone and substituted xanthones, diethoxy-acetophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, diethoxyxanthone, chloro-thio-xanthone, N-methyl diethanol-amine-benzophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone and mixtures thereof. Photoinitiators suitable for use in the present invention that will respond to visible light to initiate and induce curing include camphoroquinone peroxyester initiators and 9-fluorene carboxylic acid peroxyesters. Thermal initiators include 2,2xe2x80x2-azobisisobutyronitrile. The initiators set forth above are for the purposes of illustration only and are in no way meant to limit the initiators that may be used in the present invention.
Among the more desirable UV photoinitiators are 1-hydroxycyclohexyl phenyl ketone (sold under the tradename Irgacure 184, Ciba Specialty Chemicals, Terrytown, N.Y.), diphenyl (2,4,6-tri(methylbenzoyl) phosphine oxide and bis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819, Ciba Specality Chemicals). It has been found that a combination of these photoinitiators produce particularly good results in highly pigmented compositions, such as the colored hearing aid products of the present invention.
Photoinitiators may be employed in amounts of about 0.01% to about 10% and desirably about 0.25% to about 1.0% by weight of the total composition.
The compositions of the present invention may also employ other or additional free radical components. For example, the inventive compositions may be anaerobically cured by employing peroxy free radical initiators conventional to such cure mechanisms. In such cases, accelerators are often employed to enhance the speed at which the peroxy free radical is generated. Reducing agents for the initiator, such as saccharin, may also be employed.
Free radical initiators such as peroxy, perester and peracid compounds may also be employed. Illustrative of peroxy initiators are the diacyl peroxides such as benzoyl peroxide; dialkyl peroxides such as di-tert-butyl peroxide; ketone peroxides such as methylethyl ketone peroxide; and peresters which readily hydrolyze, e.g., tert-butyl peracetate, tert-butyl perbenzoate and di-tert-butyl diperphthalate. A particularly useful class of peroxy initiators are the organic hydroperoxides such as cumene hydroperoxide (CHP), methylethyl ketone hydroperoxide and tert-butyl hydroperoxide (TBH). Of these, cumene hydroperoxide is especially desirable. These initiators may be used in amounts of about 0.01% to about 10% by weight of the total composition, and desirably in amounts of about 0.1% to about 3% by weight of the total composition. Another useful class of initiators includes carbonyl-containing ultraviolet-activated free-radical generators, such as acetophenones, benzophenones and the benzoin ethers. Initiator combinations may also be employed.
Useful accelerators for the present invention include compounds having the following formula:
where R8 is selected from alkyl from 2 to 6 carbon atoms, cycloalkyl, aryl, alkenyl, and cycloalkenyl and R9 is selected from hydrogen, alkyl, cycloalkyl, alkenyl and cycloalkenyl, aryl, alkoxy, aryloxy, carbonyl, amino, and the following groups:
where R10 is selected from alkyl groups containing one to about 10 carbon atoms, alkenyl groups containing two to about 10 carbon atoms, and aryl groups containing up to about 10 carbon atoms. Examples of useful accelerator compounds include 1-acetyl-2-phenyl hydrazine, 1-acetyl-2(p-tolyl) para-toluene sulfonyl hydrazide, 1-formyl-2-phenyl hydrazine and combinations thereof.
Stabilizers and inhibitors may also be employed as well as chelating agents to control and prevent premature peroxide decomposition and polymerization. Among those useful inhibitors include phenols such as hydroquinone and quinones. Chelating agents may be used to remove trace amounts of metal contaminants. An example of a useful chelating agent is the tetrasodium salt of ethylenediamine tetraacetic acid (EDTA).
Other agents such as thickeners, plasticizers, fillers, elastomers, thermoplastics, and other well-known additives may be incorporated where functionally desirable.
Various colorants can be included in the inventive compositions. The term xe2x80x9ccolorantsxe2x80x9d is used to include dyes, pigments and other materials which can be used to impart color to the composition. Dyes are generally water-soluble organics, which often become water-insoluble once cured. Pigments may be organic or inorganic materials and are generally in the solid form. In particular, the compositions of the present invention are designed to work particularly well with the more dense solid pigments which are available. These pigments, due to their density and insolubility, tend to drop out of the dispersion and form a sediment in compositions to which they are added. The present invention is designed to overcome this sedimentation tendency, keep such dense insolubles in dispersion for a longer period of time and provide for color homogeneity to be re-established without substantial mixing.
Examples of useful pigments, include without limitation, white pigments, such as titanium oxide, zinc phosphate, zinc sulfide, zinc oxide and lithopone; red and red-orange pigments, such as iron oxide (maroon, red, light red), iron/chrome oxide, cadmium sulfoselenide and cadmium mercury (maroon, red, orange), ultramarine (blue, pink and violet), chrome-tin (pink) manganese (violet), cobalt (violet); orange, yellow and buff pigments such as barium titanate; cadmium sulfide (yellow), chrome (orange, yellow), molybdate (orange), zinc chromate (yellow), nickel titanate (yellow), iron oxide (yellow), nickel tungsten titanium, zinc ferrite and chrome titanate; brown pigments such as iron oxide (buff, brown), manganese/antimony/titanium oxide; manganese titanate, natural siennas (umbers), titanium tungsten manganese; blue-green pigments, such as chrome aluminate (blue), chrome cobolt-alumina (turquoise), iron blue (blue), manganese (blue), chrome and chrome oxide (green) and titanium green; as well as black pigments, such as iron oxide black and carbon black.
Combinations of pigments are generally used to achieve the desired color tone in the cured composition. Titanium and iron oxides in combination, are particularly useful in creating flesh tones for hearing aids.
The colorants may be present in the present invention in amounts sufficient to render the desired color. Desirably, colorants may be present in amounts of about 0.1 to about 10.0%, desirably about 0.2 to about 2.0% and more desirably in amounts of about 0.2 to about 0.6% by weight of the total composition. Insoluble pigments are the desired form of colorant useful in the present invention.
In addition to a curable component, a cure system and a pigment composition, the present invention includes an additive (d), which serves as a dispersion stabilizer and aids in control of the rheology of the composition. As previously stated, this additive includes a combination of an alkali metal cation and the reaction product of (i) a polyfunctional isocyanate and a member selected from the group consisting of an hydroxy and an amine; or (ii) a phosgene or phosgene derivative, and a compound having 3 to 7 polyethylene ether units terminated at one end with an ether group and at the other end with a reactive functional group selected from the group consisting of an amine, an amide, a thiol and an alcohol; or (iii) a monohydroxy compound, a diisocyanate and a polyamine. When the reaction product described in (iii) is employed, it is generally formed by first reacting a monohydroxy compound with a diisocyanate to form a mono-isocyanate adduct, and subsequently reacting the mono-isocyanate reaction product with a polyamine in the presence of an alkali metal salt and aprotic solvent, as described in U.S. Pat. No. 4,314,924, the disclosure of which is hereby expressly incorporated herein by reference. A commercially available version of the reaction product described in (iii) is believed to be BYK-410, from BYK-Chemie, Wallingford, Conn. BYK-Chemie describes this reaction product as a urea urethane.
Useful isocyanates for forming the reaction product(s) of the dispersion stabilizing additive include polyisocyanates such as phenyl diisocyanate, toluene diisocyanate, 4,4xe2x80x2-diphenyl diisocyanate, 4,4xe2x80x2-diphenylene methane diisocyanate, dianisidine diisocyanate, 1,5-naphthalene diisocyanate, 4,4xe2x80x2-diphenyl ether diisocyanate, p-phenylene diisocyanate, 4,4xe2x80x2-dicyclo-hexylmethane diisocyanate, 1,3-bis-(isocyanatomethyl) cyclohexane, cyclohexylene diisocyanate, tetrachlorophenylene diisocyanate, 2,6-diethyl-p-phenylenediisocyanate, and 3,5-diethyl-4,4xe2x80x2-diisocyanatodiphenylmethane. Still other polyisocyanates that may be used are polyisocyanates obtained by reacting polyamines containing terminal, primary and secondary amine groups or polyhydric alcohols, for example, the alkane, cycloalkane, alkene and cycloalkane polyols such as glycerol, ethylene glycol, bisphenol-A, 4,4xe2x80x2-dihydroxy-phenyldimethylmethane-substituted bisphenol-A, and the like, with an excess of any of the above-described isocyanates.
Useful alcohols for reacting with the polyisocyanates used to form the additive (iii) also include polyethyl glycol ethers having 3-7 ethylene oxide repeating units and one end terminated with an ether or an ester, polyether alcohols, polyester alcohols, as well as alcohols based on polybutadiene. The specific type of alcohol chosen and the molecular weight range can be varied to achieve the desired effect. Generally, monohydroxy compounds, straight or branched chain aliphatic or cyclic primary or secondary alcohols containing C5-25, and alkoxylated derivatives of these monohydroxy compounds are useful.
Phosgene and phosgene derivatives, such as bischloroformates, may be used to make the reaction product of the additive (iii). These compounds are reacted with a nitrogen-containing compound, such as an amine, an amide or a thiol to form the adduct. Phosgenes and phosgene derivatives may also be reacted with an alcohol to form the reaction product.
Amines which can be reacted with phosgenes or phosgene derivatives to make the reaction product of the additive (iii) include those which conform to the general formula R11xe2x80x94NH2, where R11 is aliphatic or aromatic. Desirable aliphatic amines include polyethylene glycol ether amines. Desirable aromatic amines include those having polyethylene glycol ether substitution on the aromatic ring.
For example, commercially available amines sold under the tradename JEFFAMINE by Huntsman Corporation, Houston, Tex., may be employed. Examples include JEFFAMINE D-230, JEFFAMINE D-400, JEFFAMINE D-2000, JEFFAMINE T-403, JEFFAMINE ED-600, JEFFAMINE ED-900, JEFFAMINE ED-2001, JEFFAMINE EDR-148, JEFFAMINE XTJ-509, JEFFAMINE T-3000, JEFFAMINE T-5000, and combinations thereof.
The JEFFAMINE D series are diamine based products and may be represented by:
where x is about 2.6 (for JEFFAMINE D-230), 5.6 (for JEFFAMINE D-400) and 33.1 (for JEFFAMINE D-2000), respectively.
The JEFFAMINE T series are trifunctional amine products based on propylene oxide and may be represented by:
where x, y and z are set forth below in Table A.
More specifically, the JEFFAMINE T-403 product is a trifunctional amine and may be represented by:
where x+y+z is 5.3.
(CAS Registry No. 39423-51-3)
The JEFFAMINE ED series are polyether diamine-based products and may be represented by:
where a, b and c are set forth below in Table B.
Amides useful for reacting with the phosgene or phosgene derivatives include those which correspond to the following formula:
where R12 may be an aliphatic or aromatic, substituted or unsubstituted, hydrocarbon or heterohydrocarbon, substituted or unsubstituted, having C1-36.
Alcohols useful in forming the reaction product with the phosgene or phosgene derivatives include those described above.
The alkali metal cations are usually provided in the form of a halide salt. For example, sodium, potassium and lithium halide salts are useful. In particular, sodium chloride, sodium iodide, sodium bromide, potassium chloride, potassium iodide, potassium bromide, lithium chloride, lithium iodide, lithium bromide and combinations thereof may be employed.
The reaction products of additive (iii) of the present invention are usually present in and added to the composition with an alkali metal salt, in a solvent carrier. The solvents are desirably polar aprotic solvents in which the reaction to form the reaction product was carried out. For example, N-methyl pyrrolidone, dimethylsulfoxide, hexamethylphosphoric acid triamide, N,N-dimethylformamide, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylurea, N,Ndimethylacetamide, N-butylpyrrolidone, tetrahydrofuran and diethylether may be employed.
One particularly desirable additive is the combination of a lithium salt and a reaction product which is formed by reacting a monohydroxy compound with a diisocyanate compound to form a mono-isocyanate first adduct, which is subsequently reacted with a polyamine in the presence of lithium chloride and 1-methy-2-pyrrolidone to form a second adduct. A commercially available additive of this sort is sold by BYK Chemie, Wallingford, Conn. under the trade name BYK 410. This commercially available additive is described by BYK-Chemie product literature as being a urea urethane having a minor amount of lithium chloride present in a 1-methyl-2 pyrrolidone solvent.
Desirably, the dispersion stabilizing additive is present in the inventive compositions in amounts of about 0.1% to about 2.0% and more desirably in amounts of about 0.5% to about 0.7% by weight of the total composition.
It is believed that the dispersion stabilizing component, when combined with the dispersed pigments in the inventive compositions, provides a unique mechanism for maintaining the pigments in dispersion. These combinations of components are responsible for the ability to maintain the uniformity of color during storage and eliminate the need for substantial mixing prior to use. In some instances, uniformity of the dispersion during storage may be slightly altered. In such instances, uniform dispersion of the colorant can be immediately returned by slight shaking and without a separate mixing step. Thus, the combination of components provides a sufficient xe2x80x9cnetworkxe2x80x9d or xe2x80x9cstructurexe2x80x9d which is storage stable and which maintains the suspension of the pigments in the curable composition.
The viscosities of the inventive composition can thus be formulated to be in a controlled range. Desirable ranges include Brookfield 500 to about 2,000 cps, as measured at 25xc2x0 C., RTV spindle #3, at 20 RPM for relatively low viscosity applications. High viscosities are desirable in applications such as patching or repairing hearing aid shells, or for forming hearing aid vent channels. In such cases, viscosities on the order of 5,000 to 10,000 cps Brookfield, as measured at 25xc2x0 C., RTV spindle #3 at 20 RPMs are useful. Desirably, the final compositions used to make molded articles are easily pourable at room temperature to facilitate the manufacturing process. Moreover, many manufacturing techniques used in the hearing aid industry include dispensing the curable composition using syringe-like dispensing devices. The overall rheology of the compositions, therefore, must be suitable for these dispensers. As the material is dispensed, the natural flow of the composition further prevents any settling of the pigments. However, the xe2x80x9cnetworkxe2x80x9d produced by the unique combination of the inventive components may be temporarily interrupted in this process. Nonetheless, once the composition has been deposited in the mold cavity, it regains its internal xe2x80x9cstructurexe2x80x9d which serves to maintain the pigment in dispersion.
The process of making the hollow shells includes pouring the curable composition into the mold cavity of a light-penetrable mold, the mold having an exposed, generally upward-facing surface. The composition covers a major amount of the generally upward-facing surface and fills the majority of the cavity. The surface was then exposed to ultra-violet radiation through the transparent mold surface to achieve a thin layer of cured composition having the shape of the cavity surface. Above the cured material remained uncured composition, which was then poured off to leave the cured shell. Depth of thickness of the shell was controlled using a combination of UV initiators, light intensity and time. Additional cure of the shell, if necessary, could also be achieved by exposing the shell to additional photoradiation from the open end of the cavity once the uncured liquid is removed.
The resulting shells are self-supporting, free from surface blemishes and uniform in color. They can be pigmented to match a variety of skin tones and are ideally suited for housing for hearing and components.
Other materials such as wetting agents, defoaming agents, odor masking agents, chelating agents, viscosity modifiers, stabilizers and combinations thereof.
The following examples are intended to be non-limiting illustrations of compositions of the present invention.

Dispersion stable curable compositions and method for making hollow shells using same


A two-cycle oil is disclosed comprising a polyisobutylene amine, a dispersant, a polybutene polymer, solvent and lubricating oil which exhibits improved performance.

This invention relates to a lubricant composition useful as a two-cycle oil. Two-stroke-cycle gasoline engines now range from small, less than 50 cc engines, to higher performance engines of 200 to 500 cc. The development of such high performance engines has created the need for new two-cycle oil standards and improved lubricants which satisfy these standards.
Two-cycle engines are lubricated by mixing the fuel and lubricant and allowing the mixed composition to pass through the engine. Various types of two-cycle oils, compatible with fuel, have been described in the art. Typically, such oils contain a variety of additive components in order for the oil to pass industry standard tests to permit use in two-cycle engines.
The present invention is based on the discovery that the use of a combination of polyisobutylene amine and a nitrogen containing dispersant results in an improved two-cycle oil.
Accordingly, there has been discovered a two-cycle lubricating oil composition having a Brookfield viscosity of about 2,000 to 7,500 cps at xe2x88x9225xc2x0 C. comprising an admixture of the following:
(a) 1.5-8% by weight (active ingredient basis) of a polyisobutylene amine, the polyisobutylene having an Mn (number average) molecular weight of about 400-1500;
(b) 2.5-8% by weight (active ingredient basis) of a nitrogen-containing lubricating oil dispersant being a reaction product of an oil soluble hydrocarbyl substituted carboxylic acylating agent and a polyamine;
(c) 5-30% by weight of a polybutene polymer having an Mn molecular weight of about 900-1500;
(d) 10-45% by weight of a normally liquid hydrocarbon solvent having a boiling point range of about 120-380xc2x0 C. and a flash point in the range of 55-140xc2x0 C.; and
(e) the balance an oil of lubricating viscosity.
Polyisobutylenes useful in this invention for preparing polyisobutylene amines generally have an average Mn molecular weight of about 400-1500, preferably 900-1200, and the polyisobutylene amine can be prepared by chlorination or hydroformylation of a reactive polyolefin such as polyisobutylene, and subsequent amination with ammonia, hydrocarbyl amine or diamine, hydrocarbyl polyamine, alkoxylated hydrocarbyl amines, or mixture thereof. Ammonia, ethylenediamine, propylenetriamine, diethylenetriamine, triethylenetetramine, hydroxyalkyl-ethylenediamines, hydroxyalkyl triethylenetetramines, and similar compounds can be converted to polyalkyleneamines by these procedures. Mixtures of the above and similar amines can also be used effectively. Alternatively, these amines can be prepared by chlorination or halogenation of appropriate polymeric olefins, and then converted into corresponding polyalkyleneamine derivatives using these or other known methods of manufacture. They are preferably used in amounts of 6-7 wt. % in the present invention.
Particularly preferred is a polyisobutylene amine prepared from ethylene diamine and Mn 1200 polyisobutylene (PIB). It is preferably present in an amount of about 6-7% by weight on an active ingredient basis, the additive normally being provided in a solution of mineral oil containing about 50-75% by weight PIB amine, such as about 60% by weight.
The (b) component of the two-cycle oils of this invention is a lubricating oil nitrogen-containing carboxylic dispersant present in an amount of about 2.5-8% by weight, preferably about 6-7% by weight. These percentages do not include the mineral oil carriers commonly used in the dispersant products and are therefore on an active ingredient (a.i.) basis. The active ingredient content of such dispersants is typically about 50-95% by weight.
The nitrogen-containing carboxylic dispersants include amine reaction products of hydrocarbyl-substituted carboxylic acylating agents such as substituted carboxylic acids or derivatives thereof. Typically the amines are polyamines, preferably the amines are ethylene amines, amine bottoms or amine condensates. The hydrocarbyl-substituted carboxylic acylating agent and polyamine are reacted at a temperature from about 0xc2x0 C., preferably about 50xc2x0 C., up to about 200xc2x0 C., preferably up to about 150xc2x0 C. Usually an equivalent of acylating agent is reacted with 1-4 equivalents of polyamine, preferably 2-4 equivalents.
The hydrogen-substituted carboxylic acylating agent may be derived from a monocarboxylic acid or a polycarboxylic acid. Polycarboxylic acids generally are preferred. The acylating agents may be a carboxylic acid or derivatives of the carboxylic acid such as the halides, esters, anhydrides, etc., preferably acid, esters or anhydrides, more preferably anhydrides. Preferably the carboxylic acylating agent is a succinic acylating agent.
The hydrocarbyl-substituted carboxylic acylating agent includes agents which have a hydrocarbyl group derived from a polyalkene. The polyalkene is characterized as containing from at least about 8 carbon atoms, preferably at least about 30, more preferably at least 35 up to about 300 carbon atoms, preferably 200, more preferably 100. In one embodiment, the polyalkene is characterized by an Mn (number average molecular weight) value of at least about 500. Generally, the polyalkene is characterized by an Mn value of about 500 to about 5000, preferably about 800 to about 2500. In another embodiment Mn varies between about 500 to about 1200.
Preferred for use in the oils of this invention are polyisobutenyl succinimide dispersants where the polyisobutenyl group has an Mn of about 450-1500, more preferably 900-1200, especially about 950.
The polyalkenes include homopolymers and interpolymers of polymerizable olefin monomers of 2 to about 16 carbon atoms; usually 2 to about 6, preferably 2 to about 4, more preferably 4. The olefins may be monoolefins such as ethylene, propylene, 1-butene, isobutene, and 1-octene; or a polyolefinic monomer, preferably diolefinic monomer, such 1,3-butadiene and isoprene. Preferably, the interpolymer is a homopolymer. An example of a preferred homopolymer is a polybutene, preferably a polybutene in which about 50% of the polymer is derived from isobutylene. The polyalkenes are prepared by conventional procedures.
The hydrocarbyl-substituted carboxylic acylating agents are prepared by a reaction of one or more polyalkenes with one or more unsaturated carboxylic reagent. The unsaturated carboxylic reagent generally contains an alpha-beta olefinic unsaturation. The carboxylic reagents may be carboxylic acids per se and functional derivatives thereof, such as anhydrides, esters, amides, imides, salts, acyl halides, and nitriles. These carboxylic acid reagents may be either monobasic or polybasic in nature. When they are polybasic they are preferably dicarboxylic acids, although tri- and tetracarboxylic acids can be used. Specific examples of useful monobasic unsaturated carboxylic acids are acrylic acid, methacrylic acid, cinnamic acid, crotonic acid, 2-phenylpropenoic acid, etc. Exemplary polybasic acids include maleic acid, fumaric acid, mesaconic acid, itaconic acid and citraconic acid. Generally, the unsaturated carboxylic acid or derivative is maleic anhydride or maleic or fumaric acid or ester, preferably, maleic acid or anhydride, more preferably maleic anhydride.
The polybutene polymer useful as component (c) in the two-cycle lubricating oil compositions of this invention is a mixture of poly-n-butenes and polyisobutylene which normally results from the polymerization of C4 olefins and generally will have a number average (Mn) molecular weight of about 900 to 1500 with a polyisobutylene or polybutene having a number average molecular weight of about 950 to 1300 being particularly preferred for component (c). The preferred amount is 7-8 wt. % in the two-cycle oils of the invention. Most preferable is a mixture of polybutene and polyisobutylene having a number average molecular weight of about 950. Number average molecular weight (Mn) is measured by gel permeation chromatography. Polymers composed of 100% polyisobutylene or 100% poly-n-butene are also within the scope of this invention and within the meaning of the term xe2x80x9ca polybutene polymerxe2x80x9d.
A preferred polybutene polymer is a mixture of polybutenes and polyisobutylene prepared from a C4 olefin refinery stream containing about 6 wt. % to 50 wt. % isobutylene with the balance a mixture of butene (cis- and trans-) isobutylene and less than 1 wt. %. butadiene. Particularly, preferred is a polymer prepared from a C4 stream composed of 6-45 wt. % isobutylene, 25-35 wt. % saturated butenes and 15-50 wt. % 1- and 2-butenes. The polymer is prepared by Lewis acid catalysis.
The solvents useful in the present invention as the (d) component may generally be characterized as being normally liquid petroleum or synthetic hydrocarbon solvents having a boiling point range of about 120-380xc2x0 C. at atmospheric pressure (ASTM D2887). Such a solvent should also have a flash point in the range of about 55-140xc2x0 C. Typical examples include kerosene, hydrotreated kerosene, middle distillate fuels, isoparaffinic and naphthenic aliphatic hydrocarbon solvents, dimers, and higher oligomers of propylene butene and similar olefins as well as paraffinic and aromatic hydrocarbon solvents and mixtures thereof. Such solvents may contain functional groups other than carbon and hydrogen provided such groups do not adversely affect performance of the two-cycle oil. Preferred is an aliphatic hydrocracked light hydrocarbon distillate having a boiling point range of about 199-288xc2x0 C. and a viscosity of 1.71 cSt at 40xc2x0 C. The solvents are present in amounts of from 10-45% by weight, preferably about 18-20% by weight.
The (e) component of the lubricating compositions of this invention is an oil of lubricating viscosity, that is, a viscosity of about 55-180 cSt at 40xc2x0 C.
These oils of lubricating viscosity for this invention can be natural or synthetic oils. Mixtures of such oils are also often useful.
Natural oils include mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils.
Synthetic lubricating oils include hydrocarbon oils such as polymerized and interpolymerized olefins alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof.
Oils made by polymerizing olefins of less than 5 carbon atoms and mixtures thereof are typical synthetic polymer oils. Methods of preparing such polymer oils are well known to those skilled in the art as is shown by U.S. Pat. Nos. 2,278,445; 2,301,052; 2,318,719; 2,329,714; 2,345,574; and 2,422,443.
Alkylene oxide polymers (i.e., homopolymers, interpolymers, and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc.) constitute a preferred class of known synthetic lubricating oils for the purpose of this invention, especially for use in combination with alkanol fuels. They are exemplified by the oils prepared through polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl polypropylene glycol ether having an average molecular weight of 1000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1000, diethyl ether of polypropylene glycol having a molecular weight of 1000-1500, etc.) or mono- and polycarboxylic esters thereof, for example, the acetic acid esters mixed C3-C8 fatty acid esters, or the C13 Oxo acid diester of tetraethylene glycol.
Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, octyl alcohol, dodecyl alcohol, tridecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol, etc.). Specific examples of these esters include dioctyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisoctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like.
Esters useful as synthetic oils also include those made from C5-C18 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethyl propane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc.
Unrefined, refined and rerefined oils, either natural or synthetic (as well as mixtures of two or more of any of these) of the type disclosed hereinabove can be used in the lubricant compositions of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from primary distillation or an ester oil obtained directly from an esterification process and used without further treatment would be an unrefined oil. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Many such purification techniques are known to those of skill in the art such as solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Rerefined oils are obtained by processes similar to those used to obtain refined oils which have been already used in service. Such rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additive and oil breakdown products.
Oils of this invention may also contain small proportions of various special purpose conventional lubricating oil additives.
Additional conventional additives for lubricating oils which may be present in the composition of this invention include viscosity modifiers, corrosion inhibitors, oxidation inhibitors, friction modifiers, dispersants, antifoaming agents, antiwear agents, lube oil flow improvers, pour point depressants, detergents, rust inhibitors and the like.
Typical oil soluble viscosity modifying polymers will generally have weight average molecular weights of from about 10,000 to 1,000,000 as determined by gel permeation chromatography.
Corrosion inhibitors are illustrated by phosphosulfurized hydrocarbons and the products obtained by reacting a phosphosulfurized hydrocarbon with an alkaline earth metal oxide or hydroxide.
Oxidation inhibitors are antioxidants exemplified by alkaline earth metal salts of alkylphenol thioesters having preferably C5-C12 alkyl side chain such as calcium nonylphenol sulfide, barium t-octylphenol sulfide, dioctylphenylamine as well as sulfurized or phospho sulfurized hydrocarbons. Also included are oil soluble antioxidant copper compounds such as copper salts of C10-C18 oil soluble fatty acids.
Friction modifiers include fatty acid esters and amides, glycerol esters of dimerized fatty acids and succinate esters or metal salts thereof.
Pour point depressants also known as lube oil flow improvers can lower the temperature at which the fluid will flow and typical of these additives are C8-C18 dialkyl fumarate vinyl acetate copolymers, which are preferred in amounts of about 0.1 to 1.0 wt. % (active ingredient basis), polymethacrylates and wax naphthalene.
Foam control can also be provided by an anti foamant of the polysiloxane type such as silicone oil and polydimethyl siloxane.
Anti-wear agents reduce wear of metal parts and representative materials are zinc dialkyldithiophosphate and zinc diaryl diphosphate.
Detergents and metal rust inhibitors include the metal salts of sulfonic acids, alkylphenols, sulfurized alkylphenols, alkyl salicylates, naphthenates and other oil soluble mono and dicarboxylic acid. Neutral or highly basic metal salts such as highly basic alkaline earth metal sulfonates (especially calcium and magnesium salts) are frequently used as such detergents. Also useful is nonylphenol sulfide. Similar materials made by reacting an alkylphenol with commercial sulfur dichlorides. Suitable alkylphenol sulfides can also be prepared by reacting alkylphenols with elemental sulfur.
Also suitable as detergents are neutral and basic salts of phenols, generally known as phenates, wherein the phenol is generally an alkyl substituted phenolic group, where the substituent is an aliphatic hydrocarbon group having about 4 to 400 carbon atoms.
The oils of this invention are prepared by simply combining and admixing the aforesaid ingredients at room temperature and a further aspect of this invention are oils prepared by mixing together the aforesaid ingredients (a), (b), (c), (d) and (e).
An advantage of the two-cycle oils of this invention is that they satisfy relevant tests for both land-based equipment, such as snowmobiles, and for water-cooled marine engines. A particular advantage is the fact that the oils of this invention do not contribute to the clogging of variable exhaust systems used in land-based equipment which has been observed with many conventional two-cycle formulations used heretofore in equipment such as snowmobiles.
The lubricating oil compositions of the present invention will mix freely with the fuels used in such two-cycle engines. Admixtures of such lubricating oils with fuels comprise a further embodiment of this invention. The fuels useful in two-cycle engines are well known to those skilled in the art and usually contain a major portion of a normally liquid fuel such as a hydrocarbonaceous petroleum distillate fuel, e.g., motor gasoline, especially lead-free gasoline, as defined by ASTM specification D-439-73. Such fuels can also contain non-hydrocarbonaceous materials such as alcohols, ethers, organo nitro compounds and the like, e.g., methanol, ethanol, diethyl ether, methylethyl ether, nitro methane and such fuels are within the scope of this invention as are liquid fuels derived from vegetable and mineral sources such as corn, alpha shale and coal. Examples of such fuel mixtures are combinations of gasoline and ethanol, diesel fuel and ether, gasoline and nitro methane, etc.
The lubricants of this invention are used in admixture with fuels such as lead-free gasoline, in amounts of about 20-250 parts by weight of fuel per 1 part by weight of lubricating oil, more typically about 30-100 parts by weight of fuel per 1 part by weight of oil.

Two-cycle lubricating oil containing polyisobutylene amine


Methods and apparatus for enhancing the capabilities of ultrasonic techniques through use of ultraharmonics are provided.

Conventional diagnostic ultrasound techniques such as B-mode imaging are usually based on processing ultrasonic waves at their fundamental frequency (f0). Using these ultrasound techniques, one can non-invasively and safely generate real-time images and Doppler data. However, the received signals are at times weak in contrast.
Until recently, ultrasonography lacked substances to be administered to patients to improve or increase the diagnostic yield. However, some contrast agents, most of which consist of gas microbubbles, have been introduced for use in ultrasound imaging. Gas microbubbles act as echo-enhancers by a similar mechanism to that for determining echoscattering in other cases of diagnostic ultrasound. Specifically, the backscattering echo intensity is proportional to the change in acoustic impedance between the blood and the gas making the bubbles. The difference in acoustic impedance at this interface is very high. In fact, all of the incident sound is reflected. However, the acoustic wave reflection is still insufficient to determine a strong enhancement since the microbubbles are very small and sparse within the circulation. Further, reflectivity is proportional to the fourth power of a particle""s diameter and directly proportional to the concentration of the particles themselves (Calliada et al. Eur. J. Radiol. 1998 27(2):S157-60).
Microbubbles reached by an ultrasound signal resonate with a specific resonance frequency depending on the microbubble diameter. However, the fundamental resonance frequency is not the only frequency the bubble radiates. Multiple frequencies of the fundamental one are also emitted. These harmonic frequencies have decreasing intensity. However, the second frequency, known as the second harmonic, has been extensively used for diagnostic purposes. For example, it has been demonstrated that at very low pressures of approximately 20 kPa, there is a 17.5 to 26 dB enhancement in the second harmonic signals from ALBUNEX(trademark), a contrast agent consisting of microspheres of human serum albumin suspended in a 5% solution of the same developed by Molecular Biosystems, San Diego, Calif. USA (Schrope, A. B., Newhouse, L. V. Ultrasound Med. Biol. 1993 9(7):567-579). Second harmonic imaging also permits imaging of extremely small vessels which can be missed with conventional methods (Calliada et al. Eur. J. Radiol. 1998 27(2):S157-60). Accordingly, second harmonics have been suggested as a route to exploit the diagnostic benefits of contrast imaging (Burns et al. Radiology 1992 182(P):142; Goldberg, B. B. Ultrasound Contrast Agents Martin Dunitz Ltd, London, 1997; de Jong et al. Ultrasonics 1994 32(6):447-453).
Apart from emitting widely known 2nd harmonics and other higher harmonics, bubbles also emit subharmonics and ultraharmonics. Subharmonic detection of resonating microbubbles has been described (Lotsberg et al. 1996 99(3):1366-1369; Leighton, T. G.; The Acoustic Bubble Academic press, San Diego, 1994, p 413-424; Forsberg, F. and Shi, T. W. New Aspects of Harmonic and Subharmonic Imaging. Proc. Symp. The Leading Edge in Diagnostic Ultrasound. Atlantic City, p 24-27, May 19, 1998).
It has now been found that ultraharmonics can be effectively measured in objects subjected to ultrasonic techniques and that measurement of ultraharmonics enhances the capabilities of these techniques. For example, it has now been demonstrated that measurement of ultraharmonics of ultrasound contrast agents in ultrasonic techniques enhances the capabilities of ultrasonic contrast based techniques.
An object of the present invention is to provide a method of enhancing the capabilities of ultrasonic techniques which comprises subjecting an object to an ultrasonic technique; and measuring the ultraharmonic resonance in the object. In a preferred embodiment, the object comprises an ultrasound contrast agent capable of producing the ultraharmonic resonance. Alternatively, the object may comprise free microbubbles, echogenic scatteres or reflectors capable of producing the ultraharmonic resonance, or cells, tissues or a whole body.
Another object of the present invention is to provide ultrasound instruments and systems which measure ultraharmonics to enhance the capabilities of ultrasonic techniques.
In addition to the fundamental frequency (f0) generated by ultrasonic techniques, objects when subjected to ultrasonic techniques also generate subharmonic, harmonic and even ultraharmonic (3/2f0, 5/2f0, etc.) frequencies. Unlike the fundamental frequency and harmonics which can also be generated due to non-linearity of the medium (i.e. surrounding tissue or water), ultraharmonics and subharmonics are characteristic of the object only.
Second harmonic enhancement in objects such as ultrasound contrast agents subjected to an ultrasonic technique is usually below 20 dB and decreases dramatically with increases in diagnostic pressure.
On the other hand, it has now been found that ultraharmonic enhancement of an object subjected to an ultrasonic technique is typically greater than 20 dB and usually increases with increase in diagnostic pressure. Accordingly, the present invention relates to methods and apparatus which measure ultraharmonic signals thereby enhancing the capabilities of ultrasonic techniques including, but not limited to, imaging, Doppler and perfusion techniques. These methods and apparatus are useful in both medical diagnostics and industrial applications.
As demonstrated herein measurement of ultraharmonic signals can be used to obtain higher contrast and signal to noise ratio with respect to tissue or water. In addition, measurement of ultraharmonic signals can be used to obtain higher Doppler resolution as compared to measurement of fundamental frequency. Moreover, since the first ultraharmonic is midway between the fundamental and second harmonic frequency, it is less attenuated than the second harmonics. Thus, ultraharmonics may be used to replace or augment the existing second harmonic techniques, to further harness the benefits of contrast only imaging, and other contrast based harmonic techniques, as described previously for second harmonic contrast based techniques.
Thus, by xe2x80x9cenhancing the capabilitiesxe2x80x9d of ultrasonic techniques, it is meant that higher contrast and signal to noise ratio with respect to tissue or water is achieved through measurement of ultraharmonic signals, along with higher Doppler resolution with respect to fundamental imaging techniques and decreased attenuation with respect to harmonics such as second harmonics.
In the method of the present invention, an object is subjected to an ultrasonic technique such as an imaging, Doppler or perfusion technique and the ultraharmonic signal of the object is measured. Examples of objects used in these methods include, but are not limited to, ultrasound contrast agents, free microbubbles, echogenic scatteres and reflectors, cells, tissues and whole bodies.
A series of experiments were performed to demonstrate enhanced capabilities of ultrasonics techniques wherein ultraharmonics were measured. In these experiments, a thin and flexible walled, surfactant based ultrasound contrast agent developed by insonating Span60 and Tween 80 as described in U.S. Pat. No. 5,352,436 was used as the object. Decafluorobutane or octafluoropropane gas was entrapped within the microbubbles of this thin and flexible walled, surfactant based contrast agent to produce ST68-PFC. Experiments were then performed to determine the frequency response of ST68-PFC.
The frequency content of the transmitted ultrasound signal in de-ionized (xcx9c18 M) water, 2xe2x80x3(50 mm) from the transducer was recorded as base. An increase in second harmonic and third harmonic generations was observed in deionized water due to non-linear propagation on increasing insonating pressure. Moreover, the generation of higher harmonics due to propagation in tissue is aggravated, since the non-linearity parameter B/A for tissue at diagnostic frequencies varies between 10 and 15. In pure water, B/A has been reported to equal 5 (de Jong et al. Ultrasonics. 1994 32(6):457-459). An agent such as ST68-PFC, which presents high backscattered enhancement over a broad range of frequencies (Forsberg et al. Ultrasound Med. and Biol. 1997 23(8) :1201-1208; and Forsberg et al. IEEE 1996 Ultrasonics Symposium 1337-1340), merely scatters this transformed insonating signal. This can be falsely attributed as agent generated second harmonics. In subsequent experiments at 1.29 MPa, it was observed that the agent generated second harmonic enhancement is practically nonexistent compared to the 2nd harmonics generated due to non-linear propagation. No sub or ultraharmonics were observed in these experiments.
A comparison of the base frequency content to the frequency content with agent at an insonating positive peak-pressure of 38.2 kPa and 1.29 MPa was made. The first subharmonics (f0/2), second and third harmonics (2f0, 3f0), and first, second and third sub-harmonics (3/2f0, 5/2f0, 7/2f0) in the signal from the agent could be clearly seen. However, the base signal only showed higher (second and third) harmonics. These data were primarily used for the purpose of comparing the ratio of the agent-generated harmonic signals to that of the base, using the same transducers in identical conditions. Thus, correction for the transducer bandwidth characteristics was not necessary. The signal obtained from the agent using a broad-band needle hydrophone at the a positive peak insonating pressure of 1.29 MPa was also determined.
It was found that ultraharmonic enhancement was typically greater than 20 dB (18 dB at 40 kPa for ST68-PFC), and usually increased with increase in pressure (approximately 35 dB at 0.5 MPa and 41 dB at 1.1 MPa for ST68-PFC). However, second harmonic enhancements were usually below 20 dB (typically 15 dB at 40 kPa for ST68-PFC), and decreased dramatically with increased pressure (approximately 5 dB at 0.5 MPa and 1 dB at 1.1 MPa). The first ultraharmonic (3/2f0=7.5 MHZ) signal increased with increase in dose, while the first sub-harmonic (1/2f0=2.5 MHZ) signal decreased.
Thus, in the method of the present invention capabilities of non-medical ultrasonic techniques including, but not limited to, imaging, Doppler, and perfusion techniques involving the detection of objects such as free microbubbles, contrast agents, scatteres or reflectors, or whole bodies such as fish, are enhanced by subjecting the object to the ultrasonic technique and measuring the ultraharmonic resonance of the object subjected to the ultrasonic technique.
The method of the present invention is also useful in ultrasonic techniques used in medical diagnosis. In this embodiment, it is preferred that the object comprise an ultrasound contrast agent which is administered to a patient, cells or tissue. Multiple ultrasonic contrast agents for administration to patients have been described in the prior art. For example, WO 9847540 discloses contrast agents for diagnostic ultrasound and targeted disease imaging and drug delivery comprising a dispersion of a biocompatible azeotropic mixture which contains a halocarbon; WO 9729783 discloses a contrast agent which comprises an aqueous dispersion of gas microbubbles stabilized by amphiphilic material containing phospholipid molecules having an overall net charge; U.S. Pat. No. 5,695,740, U.S. Pat. No. 5,567,415 and U.S. Pat. No. 5,701,899 disclose a pharmaceutically acceptable ultrasound contrast agent comprising microbubbles with an internal atmosphere enhanced with a perfluorocarbon gas; WO 9421301 discloses an ultrasound agent consisting of a biocompatible oil-in-water emulsion in which the oil phase comprises an oil-soluble gas/fluid or gas precursor; U.S. Pat. No. 5,637,289, U.S. Pat. No. 5,648,062, U.S. Pat. No. 5,827,502; and U.S. Pat. No. 5,614,169 disclose contrast agents comprising water-soluble, microbubble generating carbohydrate microparticles, admixed with at least 20% of a non-surface active, less water-soluble material, a surfactant or an amphiphillic organic acid; U.S. Pat. No. 5,686,060 describes an injectable suspension for ultrasonic echography comprising a carrier liquid containing at least 107 microbubbles per milliliter and at least one saturated phospholipid at a concentration below 0.01% by weight. In a preferred embodiment, ultrasonic contrast agents used in the method of the present invention comprise either free microbubbles or ST68-PFC.
Ultrasound contrast agents used in the present invention may further comprise drugs or targeting moieties encompassed within or attached to the contrast agents. Such agents are useful in drug delivery and targeting techniques. Ultrasound contrast agents comprising the drug can then be delivered to an imaged site by insonation of the agent, causing the matrix to vibrate and release drug. It is also possible that the insonation will cause the ultrasound contrast agent to rupture, releasing part or all of any contents trapped within the matrix or within the hollow interior of the agent. A targeting moiety such as an antibody specific for a selected tissue can also be attached to the ultrasound contrast agent for targeted delivery of the agent.
Also provided in the instant invention are ultrasonic instruments capable of measuring ultraharmonic signals generated by an object subjected to an ultrasonic technique. In simplest form, the ultrasound instrument that measures ultraharmonic signals comprises at least one transducer capable of transmitting an ultrasound at frequency (f0) and receiving ultraharmonics of the transmitted frequency (3f0/2). In one embodiment, the instrument comprises multiple transducers. For example, the instrument may comprise a combination of broad-band and narrow band array transducers capable of transmitting ultrasound at a selected frequency (f0) and also receiving ultraharmonic signals of the transmitted frequency (3f0/2). Thus, in this embodiment, the instrument could transmit ultrasound at a selected fundamental frequency of 5 MHZ and receive ultraharmonics of the transmitted fundamental frequency at 7.5 MHZ, thereby encompassing Doppler or any other frequency shift of the ultraharmonics. Alternatively, the instrument could transmit ultrasound at a selected fundamental frequency of 2 MHZ and receive ultraharmonics of the transmitted fundamental frequency at 3 MHZ, also encompassing Doppler or any other frequency shift of the ultra-harmonics. In a preferred embodiment, the transducer is also capable of measuring harmonic and subharmonic signals. The ultrasound instrument may further comprise a software filter connected to the transducer which processes received ultrasound signals at ultraharmonics(3f0/2) of the transmitted frequency(f0) or an analog or digital hardware filter which processes received ultrasound signals at ultraharmonics(3f0/2) of the transmitted frequency(f0).
In a preferred embodiment, the instrument comprises an ultrasonic diagnostic imaging system capable of imaging the ultraharmonic response of objects such as contrast agents, echogenic entities or tissues inside a body with reduced clutter. This system comprises a transmit controller operable to cause the elements of an array transducer to transmit wave components which are of insufficient energy to stimulate a significant harmonic response in the near field but which are focused to develop higher intensity energy at a greater depth. The system also comprises an array transducer responsive to the transmit controller for transmitting ultrasonic energy into the object at a fundamental frequency and for receiving ultrasonic echo signals at an ultraharmonic of the fundamental frequency. In one embodiment, the array transducer comprises a plurality of transducer elements for transmitting ultrasonic energy at a fundamental frequency and for receiving ultrasonic echo signals at an ultraharmonic of the fundamental frequency. In this embodiment, the transducer elements exhibit a response characteristic which encompasses both the fundamental frequency and the ultraharmonic of the fundamental frequency. A beamformer which processes echo signals from the transducer elements of this array transducer to form coherent echo signals is also used in the system along with a circuit for passing ultraharmonic frequency echo signals to the substantial exclusion of signals at the fundamental frequency and higher harmonics such as second harmonics. In one embodiment, the circuit for passing ultrasonic echo signals at an ultraharmonic of the fundamental frequency comprises a filter defining a passband which includes the ultraharmonic frequency to the substantial exclusion of the fundamental frequency and higher harmonics. This filter also substantially excludes multipath clutter at the fundamental frequency. For example, a programmable digital filter can be used. The system also comprises an image processor, responsive to ultraharmonic frequency echo signals passed by said circuit, for producing an ultrasonic ultraharmonic image. For example, a B mode processor which produces ultraharmonic images can be used. It is preferred that the B mode processor include an amplitude detector for detecting the envelope of the ultraharmonic echo signals.
Ultrasonic diagnostic imaging systems for imaging the ultraharmonic response of objects inside a body or any heterogeneous nonlinear medium which exhibit depth dependent attenuation of ultrasonic energy can also be developed. The system comprises a transmit controller operable to cause the elements of an array transducer to transmit wave components, the energy of which is distributed over the array in the near field and becomes focused to develop ultraharmonic frequency components at a focal depth. The system also comprises a transducer array responsive to the transmit controller for transmitting ultrasonic energy into the body or other medium at a fundamental frequency. In a preferred embodiment, the fundamental frequency is equal to or less than 6 MHZ. The transducer array also receives ultrasonic echo signals from the object at an ultraharmonic of the fundamental frequency, preferably equal to or less than 9 MHZ or 15 MHZ. In another embodiment, the transducer array transmits ultrasonic energy into the body at a fundamental frequency which is equal to or less than 3 MHZ and the transducer array receives ultrasonic echo signals at an ultraharmonic of the fundamental frequency which is equal to or less than 4.5 MHZ. In yet another embodiment, the transducer array transmits ultrasonic energy into the body at a fundamental frequency which is less than 2 MHZ and the transducer array receives ultrasonic echo signals from tissue at a harmonic of the fundamental frequency which is less than 3 MHZ. This system further comprises a means for digitizing the received ultrasonic echo signals; a digital beamformer for forming coherent echo signals from the digitized ultrasonic echo signals; a filter which passes ultraharmonic echo signals to the substantial exclusion of fundamental frequency signals and higher harmonics; and an image processor which is responsive to the ultraharmonic echo signals from which fundamental frequency signals have been substantially excluded and which produces an ultrasonic image from the ultraharmonic echo signals. In a preferred embodiment, the filter comprises a programmable digital filter which is programmed to pass a band of ultraharmonic echo signals to the substantial exclusion of signals of the fundamental frequency, including the substantial exclusion of multipath clutter at said fundamental frequency. Accordingly, this system also substantially reduces the multipath clutter of the image. This ultrasonic diagnostic imaging system of the present invention is particularly useful in ultrasonic techniques of tissue or cells of the body with or without any ultrasound contrast agents.
The systems of the present invention are useful in producing an ultrasonic image or Doppler signals from the ultraharmonic response of an object such as a tissue or contrast agent in the interior of the body or any medium. In this method, ultrasonic energy is transmitted from the elements of an array transducer into the body or medium at a fundamental frequency in wave components emanating over a plurality of elements in the near field. The wave components are focused to develop ultraharmonic frequency components at a greater death. Ultrasonic echo signals returned at an ultraharmonic of the fundamental frequency are also received by this array transducer and coherent echo signals from the received ultrasonic echo signals are formed. The steps of transmitting and receiving can be accomplished using an ultrasonic probe with a transducer array to transmit fundamental frequency ultrasonic energy and receive ultraharmonic echo signals from the object. An ultrasonic image of the signals which substantially excludes the fundamental frequency and harmonic signals is then produced and displayed. By measuring the ultrasonic signal via this system, multipath clutter in the image is substantially reduced.

Method of enhancing ultrasonic techniques via measurement of ultraharmonic signals


A lifting rack for elevating motorcycles or other two-wheeled vehicles for ease of maintenance. The rack comprises a channel with a base plate that may be laid flat on a ground or floor surface, and upstanding side walls that provide lateral stability for a two-wheeled vehicle as the vehicle wheels are positioned on the base plate. The rack also comprises ground or floor surface engaging rails. A linkage mechanism connects the rails to the channel. A hydraulic motor, anchored on the rails, applies a lifting force to the linkage elements, thereby creating a vertical lift force component, the base plate supporting the vehicle wheels as the vehicle lifted. One end of the channel may be separated from the main portion of the channel and separately articulated on the rails, whereby one vehicle wheel may overhang the end of main channel portion.

The invention relates to lift racks for maintenance of a two-wheeled vehicle.
In servicing a motorcycle, it is necessary or desirable to lift the motorcycle to make undercarriage vehicle components accessible for repair or maintenance purposes. Prior art mechanisms for lifting motorcycles usually include a platform connected to a base by an articulated linkage. The motorcycle is loaded on the platform when the platform is lowered toward the ground or floor surface that supports the lift. Provision is made in such known construction for actuating the linkage that connects the platform to the base using a fluid motor. An example of a construction of this type may be seen by referring to a catalog published by Autec Hofbruggen BV in the Netherlands. Lifts similar to the Autec lift have been used also to raise water craft and garden tractors for maintenance purposes. An example of a lift of this kind is disclosed in U.S. Patent Design 344,835.
In the prior art constructions, the lift track and the mechanism for lifting the motorcycle require the operator to wheel the motorcycle onto the platform which is raised from the surface that supports the lift track. Because of the weight of the vehicle, it is necessary to use a ramp device for raising the vehicle to the level of the platform before the platform is raised. Lift mechanisms of conventional design further require special stabilizing structural members for the motorcycle, which add to the overall weight of the lift. Further, the overall width of conventional lift mechanisms, including the load-supporting platform, is usually much wider than the transverse width of the motorcycle itself. This encumbers access to the undercarriage of the motorcycle for maintenance purposes.
It is an objective of the invention to provide a medium-weight lift rack assembly for a motorcycle and other two-wheeled vehicles wherein the vehicle can be wheeled by the operator onto the rack before it is raised. The operator thus can drive or roll the motorcycle onto the track and deploy the usual side stand prior to raising of the lift rack. The operator then can dismount the vehicle and secure the motorcycle properly before it is elevated.
The lift rack of the invention prevents transverse deviation of the motorcycle wheels by providing side walls on the base of the lift rack, which center the motorcycle on the lift rack.
The overall width of the lift track of the invention is narrower than the width of the motorcycle itself. This provides an unobtrusive profile for the lift rack and permits unencumbered access to the undercarriage of the motorcycle for maintenance purposes.
The motorcycle is lifted as the lift rack engages the motorcycle tires rather than the frame of the vehicle itself. This prevents possible damage to vehicle body work or paint.
The lift rack of the invention may be used in tandem with another lift rack of the same design to create a lifting mechanism for four-wheeled vehicles, such as lawn tractors or four-wheel all-terrain vehicles.
The lift rack includes an upper channel that is engaged by the tires of the vehicle. The upper channel has a base plate that rests on the ground or floor when the lift rack is lowered. A forward portion of the channel may be detachable from a main channel section. This permits the motorcycle front wheel to overhang the main track section for purposes of tire service or wheel removal without the necessity for using an external jack device. Rear wheel servicing also can be accommodated by reversing the position of the vehicle on the channel.
The lift rack assembly includes ground or floor engaging rails that are connected to the upper channel by parallelogram linkage elements or arms. A fluid motor, supported by the rails, activates the linkage elements to raise the upper channel.
A further feature of the invention is its lightweight design, which facilitates storage when the rack is not in use. Compared to known lift rack designs, the invention also improves the degree of safety in servicing the motorcycle because of its improved stabilizing characteristics.
The lift rack of the present invention can be adapted readily for storage by employing casters mounted on its forward end, thereby permitting an operator to raise the opposite end of the lift rack so that the assembly can be wheelbarreled to a storage location. A stabilizer bar is connected to the rails to provide lateral stability. A tie-down bar is connected to the upper channel to provide an anchor for tie-down straps connected to the vehicle.

Powered lift for raising a two-wheeled vehicle


An integrated circuit voltage regulator uses a simple CMOS structure to implement a High Unity Gain BandWidth voltage regulator providing for low voltage ripple at the output of the regulator up to high frequencies in the hundreds of MHz range. A transconductor first stage is followed by an impedance cancellation second stage allowing DC gain to be set completely independently of the bandwidth.

Field
The present invention relates generally to voltage regulation for Integrated Circuit technology, and more specifically to efficient noise immune voltage regulation in Integrated Circuits requiring.
Background
A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism or electronic components. Depending on the design, it may be used to regulate one or more Alternating Current (AC) or Direct Current (DC) voltages. Electronic voltage regulators are found in devices such as computer power supplies where they stabilize DC voltages used by the processor and other elements. The stability of the output voltage can be significantly increased by using an operational amplifier. The operational amplifier drives its transistor with more current if the voltage at its inverting input drops below the output of the voltage reference at a non-inverting input. A voltage divider allows selection of an arbitrary output voltage.
Traditional apparatus and methods for electronic operational amplifier voltage regulation in Integrated Circuits (ICs) typically require physical separation between analog and digital circuit blocks as well as individual external bypass capacitors for each voltage regulation node requiring an individual external pin interface. These external bypass capacitors at the output of the integrators quiet the regulated voltage node by filtering noise from the power supply signal line.
A linear power line regulator may also step a higher voltage down to a lower voltage used as a power supply for specific digital hardware blocks, traditionally in conjunction with a an external capacitor to filter environmental noise. However, an external capacitor for each internal voltage regulation node necessitates an external pin on the Integrated Circuit package for each internal regulation node of the IC, generating size and complexity issues as well as additional manufacturing costs. For example, in implementations having multiple digital and analog functional blocks requiring ten internal regulation nodes, an additional ten external pins and associated capacitors must be added to the IC package. Due to noise in the environment, many voltage regulators are inefficiently required in order to quiet the analog blocks, requiring more and more regulators and their associated external pins and capacitors coupled to ground.
Unfortunately, such external bypass capacitors create inductances between the internal node, the capacitor and the Printed Circuit Board (PCB) substrate generating concomitant parasitic signals that impair performance of high frequency circuits. The external capacitor effectively filters noise and parasitics at low frequencies but not at high frequencies because those components that are introduced through the IC package and the PCB substrate inherently reduce the efficiency of the capacitor. Above certain frequencies, the quality factor is reduced because of the components in series with the capacitor, which can no longer effectively filter noise and parasitic signals from the environment. In other words, an ideal capacitor with no parasitic signals around it has a linear transfer function. It attenuates at a frequency N. Attenuation increases linearly with increase in frequency. If no additional components are introduced around the capacitor, the transfer function remains linear. Adding resistors or other components in series with the capacitor causes the transfer function to become non-linear as it reaches a threshold operational frequency, flattening out the transfer function and degrading the ability of the capacitor to filter parasitic noise. At higher frequencies, the capacitor loses its efficiency and no longer acts as a filter. Many of the functional hardware blocks beneficially protected by voltage regulation are operating at high frequencies, traditionally forcing physical IC separation of analog and digital blocks, separate ground planes and implementation of External Power Management Integrated Circuit (PMIC) devices.
Complexity and manufacturing costs drive an ever increasing need for integration of functionality and analog and digital hardware blocks in ICs, which requires an internal solution capable of guaranteeing enough noise immunity for high frequency analog sensitive blocks to reside within an IC device without being contaminated by noise from other hardware blocks. Inversely, noise generated by these other blocks must be contained within those blocks.
There is therefore a need in the art for noise immune voltage regulation at high frequencies suitable for SOC implementation without the need for individual external bypass capacitors, their associated performance degradation, and multitude of external interface pins on the IC package, while also providing enough gain for operation.

High unity gain bandwidth voltage regulation for integrated circuits