Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D17/00—Detergent materials or soaps characterised by their shape or physical properties
  • C11D17/0008—Detergent materials or soaps characterised by their shape or physical properties aqueous liquid non soap compositions
  • C11D17/0017—Multi-phase liquid compositions
  • C11D17/0021—Aqueous microemulsions
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/66—Non-ionic compounds
  • C11D1/825—Mixtures of compounds all of which are non-ionic
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/66—Non-ionic compounds
  • C11D1/83—Mixtures of non-ionic with anionic compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/66—Non-ionic compounds
  • C11D1/835—Mixtures of non-ionic with cationic compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/43—Solvents
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
  • C23G5/06—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using emulsions
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/02—Anionic compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/38—Cationic compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/38—Cationic compounds
  • C11D1/62—Quaternary ammonium compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/66—Non-ionic compounds
  • C11D1/72—Ethers of polyoxyalkylene glycols
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/66—Non-ionic compounds
  • C11D1/75—Amino oxides
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D1/00—Detergent compositions based essentially on surface-active compounds; Use of these compounds as a detergent
  • C11D1/88—Ampholytes; Electroneutral compounds

Definitions

• This invention relates to compositions and methods for removing silicone wax, grease, grime, adhesives and the like from hard surfaces such as automobile finishes.
• VOCs Volatile Organic Compounds
• U.S. Patent No. 4,446,044 to Rutkiewic, et. al. describes a water-in-oil emulsion, used as a cleaning fluid for automotive finish surfaces. Rutkiewic, et. al. make the explicit statement at column 3, lines 23-26 that "in order for this particular emulsion to be efficacious as a cleaner, it is necessary that the water, not the organic solvent, constitute the internal phase.” This suggests that the emulsion must be of the water-in-oil type for effective cleaning.
• U.S. Patent No. 3,983,047 to Vinson describes a de ⁇ al removal composition for loosening adhesive bonded to an airplane. The composition contains mostly organic solvent well above the regulated VOC limit and is a solvent mixture.
• U.S. Patent No. 4,146,499 to Rosano discloses a method of preparing microe ulsions for a wide variety of applications including the use of hydrophobic substance such as hydrocarbon substances including mineral spirits for "their ability to dissolve most hydrophobic substance.”
• U.S. Patent No. 4,909,962 to Clark describes a composition used primarily for laundry pre-spotting that is a microemulsion comprising organic solvent and a selection of nonionic surfactants and cosolvents.
• Component C of this composition is a supplementary nonionic surfactant comprising an amine oxide or an alkyl phenol ethoxylate. See especially col. 2, line 59 and Examples 7 and 8 at col. 8.
• These compositions are specifically intended to be used on fabrics that will be followed by a regular washing, thereby infinitely diluting the composition with a water ratio of at least 100 parts water to 1 part composition.
• the optional use of these compositions as all-purpose cleaners for hard surfaces is disclosed at column 3, lines 21 to 30.
• compositions used comprises an organic solvent, a minor amount of an inorganic solid absorbent powder, an water-in-oil surfactant and an oil-in-water surfactant sufficient to reverse the emulsion to a water external phase upon addition of water.
• the emulsion was initially provided in an oil external phase because it was believed that this was necessary to insure that the organic solvent was exposed to the adhesive residue.
• compositions to clean difficult-to-remove contaminants from hard surfaces safely while at the same time satisfying stringent VOC requirements.
• Such compositions preferably should be easily removed from the surface to be cleaned so as not to leave any residue.
• Water-based cleaners may be washed from the surface to be cleaned with excess water, but this is undesirable because this process requires an additional step and can leave water running from the interstices of joints in the structure that must be dried before painting. Water flushing is particularly undesirable when cleaning automobile surfaces for refinishing.
• the present invention provides a method of removing silicone wax, grease, grime, adhesives and other such residues from hard surfaces such as tile, windows, plastic, metal and painted surfaces with an oil-in-water microemulsion comprising applying to such surfaces an effective amount of a composition comprising an organic solvent or solvent blend having a solubility parameter of between about 6.9 and 8.9 (cal/cm 3 ) 1 / 2 , sufficient surfactant to support a stable microemulsion, and water in an amount sufficient to provide a total VOC content of less than 200 grams/liter.
• the microemulsion is allowed to soften and otherwise ease removal of the silicone wax, grease, grime, and the like from the surface.
• microemulsion and the residue may be removed from the surface by wiping with a dry wiping material.
• the microemulsion used in the present method yields surprising cleaning power with a small amount of volatile organic solvent, and without the need for large amounts of detergent, harsh pH conditions or the like.
• the method of the present invention is specifically adapted to the particular performance requirements of the operation to be performed.
• the surface to be cleaned is soiled by oil, grease, wax or the like and is to be repainted or otherwise refinished
• Such cleaning is particularly important in the repainting of automobile surfaces.
• residues will lead to "fish eyes," or noticeable bumps in the painted surface.
• the microemulsion when used in accordance with the present invention, may be applied to the surface to be treated and effectively wiped away using only a dry wiping material. No additional cleanup, such as a water wash, is required to remove any trace cleaner.
• the standard of desired cleaning may not need to be as high as for surfaces to be repainted, because adhesive will likely be applied to the same surface. In such applications, however, good cleaning is still important to avoid adhesive failure due to adhesive or surfactant residue remaining on the surface.
• the microemulsion is applied to the surface to be treated and effectively wiped away using only a dry wiping material without additional cleanup.
• the oil-in-water microemulsion used in the present invention provides good cleaning action while at the same time satisfying environmental standards for VOCs.
• the organic solvent also does not evaporate rapidly because it is contained within discontinuous droplets distributed in the continuous aqueous phase, and is not present in quantity at the liquid-air interphase.
• the lower evaporation rate of the organic solvent is further advantageous, because tenacious waxy or adhesive residues are alleg d to soak in the solvent prior to removal.
• Environmental compatibility of the present microemulsion may be further improved with the choice of nontoxic organic components and biodegradable surfactants. Judicious choice of components also may render the microemulsion nonflammable for easier compliance with shipping regulations.
• Residue may be more easily removed from the surface to be cleaned using the present oil-in-water microemulsions by simple dry wiping techniques than using a solvent-based or water-in-oil based system.
• the present microemulsion may alternatively be removed by water washing techniques, because the microemulsion is water-dilutable. Water washing is not practical in solvent-based or water-in-oil based systems. Ease in cleanup provides significant advantages both in labor-saving and a more acceptable final product.
• the microemulsion used in the present invention is an oil-in-water microemulsion. Such microemulsions typically contain dispersed droplets of oil in the range of 50-1500A in diameter, which is visibly transparent or translucent. The microemulsion is formed spontaneously, i.e., without any energy input, with the proper selection of oil, water and surfactant components.
• the organic solvent component of the microemulsion is an organic solvent or solvent blend having a solubility parameter of between about 6.9 and 8.9.
• the specific solvent or solvent blend and the concentration of the solvent to be used is selected on the basis of the proposed application. In case of applications of cleaning silicone wax, grease, grime or the like, a low concentration of a mild hydrocarbon such as odorless mineral spirits is most suitable for cost concerns and minimal effect on fresh paint finishes. In case of adhesive remover applications or other such applications where a more aggressive cleaning action is required, a higher concentration of a more aggressive organic solvent or solvent blend is preferred.
• the solvent selected should preferably have a solubility parameter of between about 7.5 and 8.9 (cal/cm 3 ) 1 / 2 .
• Preferred aggressive solvents or solvent blends comprise at least 5% by weight of the solvent ingredient of a polar or aromatic component.
• a polar component examples include butyl acetate, acetone, glycol ether, alcohols or the like.
• the aromatic component may be toluene, xylene, naphthalene or the like.
• Suitable microemulsions typically comprise: a) an organic solvent or solvent blend having a solubility parameter of between about 6.9 and b) sufficient nonionic surfactant or surfactant blend to maintain a microemulsion, and c) water in an amount sufficient to provide a total VOC content of less than 200 grams/liter.
• the microemulsion comprises a blend of surfactants to enhance stability of the composition.
• Blends of surfactants are generally more efficient in providing stability, and thus need not be provided in as large amounts as a single surfactant.
• the surfactants typically are of diverse chemical classes, selected from cationic, zwitterionic, anionic and nonionic surfactants.
• the surfactants are selected from the nonionic surfactants, together with another surfactant selected from cationic, zwitterionic and anionic surfactants.
• the combination of cationic or zwitterionic surfactants with nonionic surfactants provides a wide range of temperature stability to the microemulsion and a low surfactant concentration.
• the surfactants serve both as emulsifiers and, to some extent, as cleaning agents.
• the surfactant combination is preferably chosen based on its removability from the surface or compatibility with subsequently applied paints and biodegradability.
• the preferred HLB of the nonionic surfactant is determined by the choice of organic solvent components and is selected to be higher than 7 to enable a spontaneously formed oil-in-water emulsion.
• Cationic or zwitterionic surfactants such as amines and their salts, quaternary ammonia salts, amine oxides, or other cationic surfactants known in the art, may be used.
• Alkylamine oxides such as cocadimethylamine oxide or lauryldimethamine oxide, are preferred because of their low toxicity.
• Typical nonionic surfactants that may be used in the microemulsions of the present invention include the polyoxyethylene surfactants, such as polyethoxylated alkyphenols and polyethoxylated linear or branched primary or secondary alcohols; the carboxylic acid esters, such as glycerol esters, polyoxyethylene esters, ethoxylated anhydrosorbitol esters, ethoxylated natural fats, oils and waxes and glycol esters of fatty acids; the carboxylic amides, such as diethanolamine condensates, monoalkanolamine condensates, polyoxyethylene fatty acid amides; and the polyalkylene oxide block copolymers, such as PluronicTM line of surfactants from BASF Corp.
• Polyethoxylated linear alcohols such as NeodalTM manufactured by Shell Chemicals and TergitolTM manufactured by Union Carbide Company, are preferred as most biodegradable.
• the microemulsion also comprises a co-surfactant to aid the solubilization of the surfactants in the solver.-., to minimize gelation during phase transition, and to provide transparency and low viscosity of the microemulsion.
• the co-surfactant is chosen based on its polarity as well as low toxicity and flammability.
• Mid chain length alcohols such as n-propanol, n-butanol, pentanol, glycols; such as propylene glycol, or glycol ethers; such as dipropylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, ethylene glycol butyl ether can be used.
• an alcohol which also acts as a solvent is additionally advantageous especially in case of the adhesive remover application.
• the solvent or solvent blend is mixed with an amount of cosurfactant equal or slightly less than the amount of surfactant to be used in the ultimate composition.
• the cationic and nonionic surfactants are added to the solvent mixture, and the resultant mixture stirred well. Water is added in aliquots with gentle stirring after each addition until the viscosity has increased and subsequently decreased to indicate a phase transition from water-in-oil to oil-in-water. From this point on, water can be added rapidly in an amount to provide the concentration desired.
• the appropriate ratio of surfactants and amount of cosurfactant is determined through routine experimentation, reducing the amount of comparatively expensive ingredients as taught herein as possible for the particular solvent or solvent blend used.
• the ratio of cationic to nonionic surfactant can be adjusted to minimize the total amount of necessary surfactant. Generally, when less cationic surfactant is used, the total amount of surfactant must be increased.
• the cosurfactant is preferably added before the addition of water because it aids the solubilization of the surfactants in the solvent and minimizes gelation during the phase transition.
• the amount of cosurfactant to be used is adjusted to provide transparency and low viscosity.
• the formulation is adjusted by changing the ratios of surfactants in the formulation. Once the ratio of surfactant and cosurfactant has been established, the concentration of each component can be lowered or raised in relationship to the solvent to optimize stability and performance.
• microemulsion Once a satisfactory formulation for the microemulsion has been determined, usually no special techniques for mixing are required. All of the ingredients may be added in any order and mixed to form the microemulsion as taught herein.
• Preferred microemulsions comprise by weight: a) 5-15% of an organic solvent or solvent blend having a solubility parameter of between about 6.9 and 8.9 (cal/cm 3 ) 1/2 , b) 8-12% of a cationic or zwitterionic surfactant, c) 4-8% of a nonionic surfactant or surfactant blend having an HLB of between about 7.5 and 10, d) 1-5% of a co-surfactant, and e) 50-82% of water, such that the total VOC content of the microemulsion is less than 200 grams/liter.
• a milder, less expensive yet effective cleaning solution is preferably provided by a composition comprising by weight:
• a stronger cleaning solution is preferably provided by a composition comprising by weight:
• nonionic surfactant having an HLB of between 7.5 and 10, and 62-74% deionized water to total 100%.
• the microemulsion can be applied with a pump spray, aerosol, or by wiping a rag, or preferably a highly absorbent, nonwoven pad, which can be rubbed onto the surface to be cleaned. Because of its low volatility, the microemulsion can be left on the surface to soak the contaminant if necessary.
• a clean rag or nonwoven pad can be used to wipe up the dissolved soil or, optionally, the surface can be rinsed with water. To assure that all of the residue is actually removed and not merely redeposited on drying of the cleaner, physical wiping of the substrate is preferred.
• the characteristics of the wiping material are chosen to act as a carrier for the application of the microemulsion to the surface to be cleaned. This material must be soft enough as not to scratch the surface, non-linting and absorbent enough to hold sufficient quantities of soil/microemulsion.
• the preferred wiping material is a surfactant-treated polypropylene nonwoven wiper.
• Adhesive can be quickly removed if its bulk has been previously removed mechanically.
• the bulk of the adhesive is removed with a 3M Striping and Molding Adhesive Removal Disc, which is a commercially available elastomeric disc that is rotatable about its axis. These disks rub off adhesive residues without harming the underlying finish by frictional contact with the peripheral surface of the disk.
• a portion of the peripheral surface of the disk is attributed to provide a renewed peripheral surface of the elastomer.
• EXAMPLE 1 A transparent microemulsion was prepared by combining the following ingredients and stirring.
• EXAMPLE 2 A transparent microemulsion was prepared by combining the following ingredients and stirring.
• Neodal 23-3 (a nonionic surfactant from Shell Oil Co.) 61.2 deionized water
• composition of example 3 was used to remove the following adhesives baked 150 F three hours onto a painted test panel that is a cold rolled steel panel painted with a base coat/clear coat paint system from DuPont, commercially available from Advanced Coating Technology, Inc.
• adhesives represent acrylate, styrene butadiene, and Neoprene type adhesives.
• the bulk of adhesive was removed with the SCOTCH-BRITE Molding Adhesive and Stripe Removal Discs, deliberately leaving white smears of adhesive to better challenge the microemulsion adhesive cleaner.
• a hand size pad of nonwoven material as moistened with the microemulsion and rubbed for a maximum of five minutes or until the adhesive was removed from an approximate 3.5 square inch area.
• EXAMPLE 4 The following microemulsions were prepared and used to remove the following adhesives after the bulk of adhesive was removed with 3M Striping and Molding Adhesive Removal Discs. Smears of adhesive were deliberately left on the surface to be cleaned to better challenge the power of the microemulsion adhesive remover. Amount of Each Component in Weight (balance is water)
• This example shows the variety of organic solvents that can be microemulsified with this basic formulation and their comparative efficiencies.
• EXAMPLE 5 The following microemulsions were prepared using 14.2 wt. % Unocal 75 solvent, the surfactants listed below and the balance of water.
• microemulsions were prepared using several more biodegradable nonionic surfactants and balanced with water.
• DPM dipropylene glycol methyl ether.
• n-pro n-propanol.
• T15-S-3 Triton 15-S-3, a nonionic surfactant from
• Neo 91-6 Neodal 91-6, a nonionic surfactant from
• T15-S-5 Triton 15-S-5, a nonionic surfactant from Union Carbide Corporation.
• Neo 23-3 Neodal 23-3, a nonionic surfactant from Shell Oil Co.
• TEST PROTOCOL The ability of compositions to clean a silicone and wax contaminated automobile panel was evaluated by the following technique. Commercial silicone and/or wax containing polishes were applied to painted panels according to directions of the manufacturer to provide a contaminated surface. The microemulsion was applied to a clean, dry pad, wiped onto the contaminated surface and wiped off with a second clean, dry pad. The panel was then repainted and the quality of the paint finish evaluated by counting the number of "fish eye" caused by poor filming and adhesion and by the cross-hatch adhesion test (ASTM D3359) . A control section was cleaned by Ditzler DX330, a commercial, pure solvent prep solvent. Panel Preparation
• Ditzler DX-330 - apply about 4 grams to Scott WypAllTM towel and apply to wax panel - wipe off with clean, dry Scott WypAll.
• Example 1 apply about 5 grams to Scott WypAll towel and apply to waxed panel - wipe off with clean, dry WypAll towel.
• ACME Aqua KlixTM same as Example 1.
• DuPont Prep Solvent II apply about 5 grams with Scott WypAll towel - let stand about 2 minutes - remove with wet WypAll towel followed by dry WypAll towel.
• BASF same as DuPont Prep Solvent II, except use two wet wipes.
• Ditzler DX-330 which is a standard solvent cleaner and does not comply with VOC standards.
• Example 1 compares favorably with the other low VOC cleaners, but accomplishes this cleaning in one step rather than two steps.
• Example 1 performed as well or better than other low VOC prep solvents.
• Example 1 no attack after 1 minute.
• the stability of the experimental microemulsions of the present invention was tested by subjecting samples to a minimum of three freeze-thaw cycles and to a minimum of one week at 50 C. Although some samples would separate into distinct phase, the transparent microemulsion could be restored with mild shaking.
• Droplet particle size was determined by dynamic light scattering using a Malvern Photon Correlation Spectrometer.

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Citations (6)

• 1992
  • 1992-04-06 CA CA002107579A patent/CA2107579A1/en not_active Abandoned
  • 1992-04-06 JP JP4509098A patent/JPH06506496A/ja active Pending
  • 1992-04-06 WO PCT/US1992/002760 patent/WO1992018600A1/en active IP Right Grant
  • 1992-04-06 EP EP92909867A patent/EP0580721B1/en not_active Expired - Lifetime
  • 1992-04-06 DE DE69217486T patent/DE69217486T2/de not_active Expired - Fee Related

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