Classifications

• • 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
  • C23G5/02—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents
• • 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
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/50—Solvents
  • C11D7/5004—Organic solvents
  • C11D7/5018—Halogenated solvents
• • 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
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/22—Organic compounds
  • C11D7/24—Hydrocarbons
• • 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
  • C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
  • C11D7/22—Organic compounds
  • C11D7/28—Organic compounds containing halogen
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/26—Cleaning or polishing of the conductive pattern

Definitions

• the present invention relates to a method and apparatus of cleaning contaminated articles and apparatus thereof and, more particularly, to the defluxing or degreasing of parts in a non-aqueous cleaning system utilizing an organic solvent for cleaning the parts and a nonflammable fluorocarbon solvent.
• Solvent vapor phase degreasing and defluxing is a process of immersing a soiled substrate (e.g., a printed circuit board or a fabricated metal, glass, ceramic, plastic, or elastomer part or composite) into a boiling, nonflammable liquid such as a chlorocarbon or chlorofiuorocarbon fluid or admixture, followed by rinsing the part in a second tank or cleaning zone by immersion or distillate spray with a clean solvent which is the same chlorocarbon or chlorofiuorocarbon as used in the first cleaning zone.
• a soiled substrate e.g., a printed circuit board or a fabricated metal, glass, ceramic, plastic, or elastomer part or composite
• a boiling, nonflammable liquid such as a chlorocarbon or chlorofiuorocarbon fluid or admixture
• Solvent cleaning of various types of parts generally occurs in batch, hoist-assisted batch, conveyor batch, or in-line type conveyor degreaser and defluxer equipment.
• Such in-line conveyor degreaser and defluxer equipment are disclosed in U.S. 5,007,179 Patent (entitled “Cold Air Lock Vapor Seal"), commonly assigned to the assignee of the present invention.
• Parts may also be cleaned in open top defluxing or degreasing equipment, such as that disclosed in U.S. Patent Application Serial No. 07/587,893, filed September 25, 1990, also commonly assigned.
• the entrance and/or exit ends of the equipment are generally in open
• hydrochlorofluorocarbon (HCFC) based solvents have been developed in the last few years to provide more environmentally acceptable alternatives to CFC based vapor phase degreasing and defluxing processes. While these materials have been shown to be excellent CFC substitutes for a variety of cleaning applications, they are considered to be an interim replacement to CFCs since they still possess a small, but finite, ozone depletion potential, although it is much lower than that of the CFCs which they are replacing. Hence, these HCFC solvents are also proposed for global phaseout in the near future. It is generally believed that organic solvents which do not contain chlorine, bromine, or iodine atoms will not contribute to stratospheric ozone depletion. However, organic chemicals which do not contain the above halogen atoms, such as hydrocarbons, alcohols, esters, ethers, ketones, etc., usually contain undesirable flammability or reactivity properties.
• Perfluorinated hydrocarbons and hydrofluorocarbons possess many desirable solvent properties: zero ozone depletion potential; stable, non-reactive, high compatibility with plastics; good water
• perfluorocarbons have been found to be very poor solvents for many common organic and inorganic soils, e.g., fluxes.
• Hydrofluorocarbons offer improved but still limited cleaning ability over perfluorocarbons as the amount of fluorine content on the molecule diminishes, but low fluorine-content hydrofluorocarbons may start to exhibit undesirable flammability properties comparable to their hydrocarbon analogs.
• hydrofluorocarbon is the active component in the removal of the fluxes, fats and oils, and dust from soiled parts.
• an organic solvent selected from hydrocarbons, alcohols, esters, and ketones may be added in an amount from 0.5 to 30 weight percent to the aliphatic hydrofluorocarbon.
• Aqueous cleaning generally involves the cleaning of a substrate or a part in an aqueous solution of detergents or surfactants, followed by multiple rinsing steps with purified water. The part is then dried by lengthy evaporation in air or by energy intensive thermal drying machines. This process is not always desirable due to the high energy cost for drying and the additional capital investment and operating cost burden to provide aqueous waste water cleanup required by state and local authorities before sewering to ground water.
• Another cleaning process semi-aqueous cleaning, consists of cleaning a substrate in a hydrocarbon solvent based on, for example, terpenes, esters, or petroleum distillates having a high affinity for oils, waxes, and greases being cleaned from the parts, with or without the aid of a surfactant.
• the cleaned substrate is rinsed of the high boiling hydrocarbon solvent with multiple rinsing steps using purified water.
• the hydrocarbon solvent is phase separated back to the wash sump while the aqueous effluent must be processed before sewering to ground water. Consequently, high costs associated with drying energy and with processing waste effluent are evident, similar to the before-mentioned aqueous cleaning process.
• a further drawback is that the hydrocarbon solvent usually possesses a flash point and this must be carefully handled or blanketed with a nonflammable
• Nitrogen gas is much more fugitive than the dense vapors of a fluorocarbon contained in a condensing zone.
• some plastics or metals may be incompatible with the aqueous rinse solvent, resulting in water absorption or rusting of the substrate.
• Another object of the invention is to provide a non-aqueous cleaning system which does not use water for rinsing, and there does not exist a necessity for aqueous waste water cleanup, and whereby said nonaqueous cleaning system can be used in cases where materials are incompatible with water.
• Still a further object is to provide a non-aqueous cleaning system avoiding the need for drying by lengthy evaporation of rinsing fluid in air or by energy intensive thermal drying methods.
• Yet a further object is to provide a non-aqueous cleaning system utilizing an organic liquid cleaning agent for cleaning the parts and a rinsing agent having at least a slight solubility for the organic cleaner for rinsing the organic cleaner from the part and which rinsing agent is capable of drying from the part using small amounts of energy.
• a non-aqueous cleaning process for removing residual soils or surface contamination from a part comprises the steps of introducing the part into contact with an organic cleaning fluid of sufficient solvency to substantially remove said contamination and then removing the part from the organic fluid for rinsing in a rinsing agent having at least some degree of solubility for the organic cleaner to remove same from the substrate.
• the substrate is immersed in the rinsing agent, sprayed with the rinsing agent or exposed to vapors of the rinsing agent, or any combination of the above.
• the non-aqueous cleaning system of this invention utilizes a two tank cleaning process wherein a first tank contains the organic solvent and a second tank contains the rinsing agent.
• the parts or substrates to be cleaned may be
• the tanks may be part of conventional or known in-line conveyorized degreasing/defluxing equipment, separate open top defluxing tanks, or open top defluxing tanks modified to contain the cleaning and rinsing tanks or sumps.
• a non-aqueous cleaning process for removing residual soils or surface contamination from parts comprises the steps of introducing the substrate or part into an organic fluid of sufficient solvency to remove residual contamination from the parts. The parts are then rinsed by contact with a second organic solvent of lesser solvency for the soils or surface contamination than exhibited by the first organic fluid solvent but having excellent solvency characteristics towards the first solvent.
• the second solvent may be chosen preferably from the fluorocarbon class of solvents which contain at least one fluorine atom attached to an organic backbone comprised of two or more carbon atoms, with optionally other atoms also attached to the backbone such as oxygen, sulfur, nitrogen, phosphorous, hydrogen, or other halogen atoms; or less preferably the rinsing agent may be chosen from other classes of solvents such as alcohols, ethers, esters, ketones, hydrocarbons, and other non-aqueous media.
• the parts are then dried by holding under an inert vapor blanket which lessens or mitigates the flammability of the first organic cleaning solvent, or, if flammable, the second rinse solvent, where such flammability masking vapor blanket may be formed by at least one of nitrogen, carbon dioxide, perfluorocarbon, hydrofluorocarbon, or hydrochlorocarbon.
• the cleaning can be done in a system where a solution of the hydrocarbon solvent and the fluorocarbon solvent is mixed together optionally with a surfactant as a solubilizing agent in a degreaser.
• a surfactant as a solubilizing agent in a degreaser.
• the fluorocarbon being more volatile, provides a flammability suppression blanket.
• the same fluorocarbon would be used in the adjacent rinse sump for an initial immersion or spray liquid rinse followed by a final rinse in the vapor.
• the cleaning can be done in a one sump system where a solution of the hydrocarbon solvent and the lower boiling fluorocarbon solvent is mixed together optionally with a surfactant as a solubilizing agent.
• a surfactant as a solubilizing agent.
• the fluorocarbon being more volatile, provides a flammability suppression blanket, and if the soiled part which has been immersed in the cleaning mixture is held in the condensing fluorocarbon vapors for a sufficiently long period of time, the part can be removed from the vapor phase clean and is dry.
• hydrocarbon solvent as used herein means any solvent which has at least one hydrogen atom and at least one carbon atom.
• the organic cleaning solvent can be selected from linear or branched alkyl or alkanol monocarboxylic or dicarboxyiic esters having at least one carbon atom in the ester moiety and such solvent most preferably having a flash point greater then 200°F(93°C), or less preferably having a flash point greater than 150°F(66°C).
• Useful esters include methyl ester and a mixture of the dimethyl esters of adipic acid, succinic acid, and glutaric acid.
• the organic fluid may also be selected from linear or cyclic hydrocarbons containing at least one olefinic bond endo or exo to the ring.
• the hydrocarbon cleaning agent may comprise pinene and/or camphene, or may comprise terpinene, limonene, terpinolene, terpineol, linaleol, and other related members of the terpene family.
• the organic cleaning solvent may also consist of linear, branched or cyclic hydrocarbons containing C 10 to C 30 species.
• the organic cleaning fluid may also consist of hydrocarbon containing olefinic moieties which have been substituted with R 1 -R 12 groups, wherein 1 -2 hydrogen atoms or alkyl groups containing 1-6 carbon atoms or both may comprise the substituted group, i.e.,
• a useful example includes 1 ,5-dimethylcyclooctadiene.
• This organic cleaning fluid may also be comprised of acyclic or cyclic monols or diols defined by the linear structure (1)
• R H, hydroxyl where n is selected from 1 to 20
• n is selected from 1 to 20
• R 1 -R 9 is defined as alkyl or hydrogen groups or mixtures thereof, and n is defined as 0 to 6.
• Useful diois include cyclohexanol and polyethylene glycol (MW 200) (a polyether diol).
• the organic fluid may also be comprised of linear, branched, or cyclic mono or polyketones, such as
• n is defined as 0 to 6 and R 1 -R 10 is defined as alkyl or hydrogen groups or mixtures thereof.
• a useful cyclic ketone include
• organic cleaning fluids applicable to this invention may be comprised of:
• R may be an alkyl group (methyl, ethyl, etc), a phenyl group, or an alkyl substituted phenyl group
• alkyl esters such as diethylphthalate of the formula:
• R 1 is chosen from the class of compounds defined by H, alkyl, or hydroxyl groups and R 2 is selected from the class of compounds defined by H or alkyl or fluoroalkyl groups.
• R 1 -R 6 is chosen from hydrogen, alkyl, fluoroalkyl, or halogen groups and combinations thereof, such as trifluorobenzene.
• Such organic cleaning solvent may also comprise mixtures of all the above organic cleaning solvents with fluorocarbons such as linear, branched, or cyclic perfluorocarbons or hydrofluorocarbons or hydrochlorofluorocarbons optionally with substituted oxygen, sulfur, nitrogen, phosphorous or other halogen atoms attached to a carbon atom and optionally with surfactant as a solubilizing agent.
• fluorocarbons such as linear, branched, or cyclic perfluorocarbons or hydrofluorocarbons or hydrochlorofluorocarbons optionally with substituted oxygen, sulfur, nitrogen, phosphorous or other halogen atoms attached to a carbon atom and optionally with surfactant as a solubilizing agent.
• the fluorocarbon rinse solvent may be selected from the class of hydrofluorocarbon or hydrochlorofluorocarbon compounds or mixtures comprised of linear, branched, or cyclic structures having a boiling point of at least 25°C to 120°C and such fluorocarbons may be optionally substituted with other functional groups chosen from the class consisting of other halogens and oxygen, sulfur, nitrogen, and phosphorous atoms
• the preferred hydrofluorocarbon compounds or the hydrochlorofluorocarbon compounds have a certain miscibility for the organic cleaning solvents in the boiling range of at least 25°C to 120°C so that at least 2 mole % of the hydrocarbon cleaning solvent is miscible with the hydrofluorocarbon fluid without obtaining phase separation.
• the hydrofluorocarbons preferably contain between 3 to 8 carbon atoms, hydrogen, and fluorine in the compound.
• the boiling point is preferably between 25°C and 120°C with at least 60 weight percent fluorine.
• the compounds preferably have a linear or branched chain.
• the present invention provides a composition for cleaning or removing residual soils or surface contamination from a part.
• the composition comprises a non-azeotropic mixture of hydrocarbon solvent and hydrofluorocarbon solvent.
• the hydrocarbon component is present in an amount of at least 2 weight percent based on the total composition and is capable of substantially removing the residual soils or surface contamination from the part.
• the hydrofluorocarbon component has a linear or branched chain structure having 3 to 7 carbon atoms and at least 60 weight percent fluorine, is capable of substantially removing any of the hydrocarbon component remaining on the part, and is less capable than the hydrocarbon component of substantially removing the residual soils or surface contamination from the part.
• an aliphatic hydrofluorocarbon is the "active" component for the removal of the fluxes, fats and oils, and dust
• the hydrocarbon component of the present cleaning compositions is capable of substantially removing the residual soils or surface contamination from a part.
• the hydrofluorocarbon component of the present cleaning compositions has excellent solvency characteristics toward the hydrocarbon component but has a lesser solvency than the
• hydrocarbon component for the soils or surface contamination.
• the rinse solvent may also be selected from compounds or mixtures comprised of other linear, branched, or cyclic alkyl or aryl alcohols, esters, nitro-, nitrocyclo-, or nitrile compounds, ethers, ketones, hydrocarbons, and other non-aqueous media.
• Figure 1 is a partial schematic view of degreasing or defluxing equipment that may be used in the multi-solvent non-aqueous cleaning system of the present invention
• Figure 2 is a schematic view depicting an alternative
• Figure 3 is a schematic view depicting a further alternative embodiment of equipment for use in the present invention
• Figure 4 is a partial schematic view of yet further alternative equipment for practicing the system of the present invention
• Figure 5 is another embodiment of equipment for use in the present invention.
• Figure 6 is a further embodiment of equipment for use in the present invention.
• the present invention is a novel non-aqueous cleaning process whereby the most attractive features of the semi-aqueous cleaning process and the solvent vapor degreasing solvent process are combined.
• a substrate or part to be cleaned e.g., a printed circuit board coated with a rosin-based flux, or a metallic or nonmetallic part coated with a petroleum, synthetic, or semi-synthetic based oil or grease
• a substrate or part to be cleaned e.g., a printed circuit board coated with a rosin-based flux, or a metallic or nonmetallic part coated with a petroleum, synthetic, or semi-synthetic based oil or grease
• a warm or ambient temperature hydrocarbon solvent tending to have a greater affinity for the soil or contaminant on the substrate than a
• the part is then rinsed by spray or immersion in a second tank or cleaning region containing a
• nonflammable fluorocarbon solvent preferably having a lower boiling point than the hydrocarbon solvent.
• the fluorocarbon solvent has at least slight solubility for the hydrocarbon solvent and therefore rinses the hydrocarbon solvent from the surface of the part.
• fluorocarbon solvent is then dried from the part surface by evaporation in a known manner.
• drying costs are minimized, waste water treatment costs and equipment and capital investments are virtually eliminated, and safety of operation is improved.
• the organic cleaning agent is preferably a hydrocarbon which may be selected from linear or branched alkyl or alkanol
• monocarboxylic esters having at least six carbon atoms in the aliphatic moiety and at least one carbon atom in the ester moiety.
• the organic hydrocarbon fluid may also be selected from linear or cyclic hydrocarbons containing at least one olefinic bond endo or exo to the ring.
• the hydrocarbon may also be pinene and/or camphene.
• the preferred hydrofluorocarbons include compounds of the empirical formula:
• the three carbon hydrofluorocarbons include tetrafluoropropanes (HFC-254), pentafluoropropanes (HFC-245), hexafluoropropanes (HFC-236), and heptafluoropropanes (HFC-227).
• Preferred three carbon hydrofluorocarbons include tetrafluoropropanes and
• Tetrafluoropropanes include the following isomers:
• Pentafluoropropanes include the following isomers:
• the preferred hydrofluorocarbons include linear or branched compounds of the empirical formula:
• the four carbon hydrofluorocarbons include pentafluorobutanes (HFC-365), hexafluorobutanes (HFC-356), heptafluorobutanes (HFC-347), octafluorobutanes (HFC-338), and nonafluorobutanes (HFC-329).
• Pentafluorobutanes include the following isomers:
• Hexafluorobutanes include the following isomers:
• Heptafluorobutanes include the following isomers:
• Octafluorobutanes include the following isomers:
• Nonafluorobutanes include the following isomers:
• the preferred hydrofluorocarbons include linear or branched compounds of the empirical formula: C 5 H n F 12-n where 1 ⁇ n ⁇ 6
• the five carbon hydrofluorocarbons include hexafluoropentanes (HFC-476), heptafluoropentanes (HFC-467), octafluoropentanes (HFC-458), nonfluoropentanes (HFC-449), decafluoropentanes (HFC-43-10), and undecafluoropentanes (HFC-42-11).
• Heptafluoropentanes include the following isomers:
• Octafluoropentanes include the following isomers:
• a most preferred octafluoropentane is CF 3 CH 2 CF 2 CH 2 CF 3 which is known in the art as HFC-458 mfcf.
• Nonafluoropentanes include the following isomers:
• Decafluoropentanes include the following isomers:
• Undecafluoropentanes include the following isomers:
• the preferred hydrofluorocarbons include linear or branched compounds of the empirical formula:
• the six carbon hydrofluorocarbons include heptafluorohexanes (HFC- 587), octafluorohexanes (HFC-578), nonafluorohexanes (HFC-569), decaf luoropentanes (HFC-55-10), undecafluorohexanes (HFC-54-11), dodecafluorohexanes (HFC-53-12), and tridecafiuorohexanes (HFC-52-13).
• HFC- 587 heptafluorohexanes
• HFC-578 octafluorohexanes
• HFC-569 nonafluorohexanes
• decaf luoropentanes HFC-55-10
• undecafluorohexanes HFC-54-11
• dodecafluorohexanes HFC-53-12
• tridecafiuorohexanes HFC-52-13
• Heptafluorohexanes include the following isomers:
• Octafluorohexanes include the following isomers:
• Nonafluorohe ixanes include the following isomers:
• Decafluorope ntanes include the following isomers:
• Undecafluorohexanes include the following isomers:
• a preferred undecafluorohexane is
• a preferred dodecafluorohexane is
• Tridecafluorohexanes include the following isomers:
• hydrofluorocarbons include linear or branched compounds of the empirical formula:
• hydrofluorocarbons include linear or branched compounds of the empirical formula
• the hydrofluorocarbon component may also be an azeotropic mixture of hydrofluorocarbon and another component as long as the azeotropic mixture is capable of substantially removing any hydrocarbon component remaining on the part and is less capable than the hydrocarbon component of substantially removing the residual soils or surface contamination from the part.
• azeotropic mixtures include CF 3 CH 2 CF 2 CH 2 CF 3 and one of the following components: methanol, ethanol, isopropanol, n- propanol, t-butanol, isobutanol, n-butanol, t-amyl alcohol,
• FIG. 1 is a partial schematic illustration of one type of apparatus which can be used in the present process.
• a vessel (10) is divided into three sumps: a cleaning sump 15, a wash sump 20, and a rinsing sump 25.
• the cleaning compartment 15 is separated by one or more walls 17,19 from the second
• Compartment 20 which contains a fluorocarbon fluid 22 heated to its boiling point by a heater 34, to provide a nonflammable condensing vapor blanket 30 or a flammability suppression blanket over all the sumps 15, 20, 25 common to vessel 10. Compartment 20 also provides an area where the bulk of the soil and organic cleaning agent can be washed from the substrate by either immersing into the fluorocarbon fluid contained in compartment 20 or by placement in a spray stream 18 of pure fluorocarbon
• the cleaning compartment 15 is adapted to contain a body of the organic cleaning solvent 24 tailored for the cleaning
• the washing compartment 20 is adapted to contain a rinsing agent 22 having at least slight solubility for the cleaning solvent 24.
• slight solubility of the rinsing fluorocarbon solvent for the hydrocarbon cleaning solvent is defined as having ⁇ 2 mole % of the hydrocarbon is soluble in fluorocarbon solvent.
• An appropriate rinsing agent 22 and one preferred in the present invention is a fluorocarbon based solvent as noted above and in the examples below.
• compartment 20 may be provided downstream from the first rinsing compartment 20, and is also adapted to contain the fluorocarbon solvent rinsing agent.
• compartment 25 is to provide a final immersion rinse for the substrate to remove trace residues of soil or cleaning solvent and also to cool the substrate so that the part is rinsed with pure condensing vapor in the vapor zone 30.
• the vapor zone 30 is formed above the respective compartments
• a cooling coil 32 of a type known in the art defines the uppermost extent of the vapor zone 32 to condense vapor for return of condensate to compartment 25.
• hydrocarbon cleaning solvent 24 and fluorocarbon rinsing fluid 22 may be chosen for their respective mutual solubilities such that some means of physical separation such as phase separation may be employed to remove built-up soils as well as to recycle clean organic solvent back to its originating sump. Therefore, with reference to Figure 1 , it is to be noted that a U-tube phase separator (not shown) or weir or skimmer may be used in conjunction with compartment 20 to separate or remove condensed hydrocarbon which will float on top of the fluorocarbon, and this separation device (not shown) may be arranged so that the excess hydrocarbon fluid will flow back to the cleaning tank 15 from the rinsing tank 20.
• the vessel 10 of Figure 1 is depicted as an open top type of defluxer or degreaser. However, it is to be understood that the vessel 10, in its schematic form, may also characterize an in-line type of degreaser or defluxer wherein conveyor means (not shown) may be used to successively convey the parts from the cleaning sump 15 to the rinsing sumps 20 and 25.
• the organic cleaning fluid in cleaning tank 15 may optionally be mixed with a fluorocarbon type solvent.
• the cleaning fluid in this case would be warmed to a sufficient temperature to boil off the fluorocarbon, where the boiling point of the fluorocarbon should be at least 10°C. lower than that of the organic hydrocarbon fluid.
• the mixture is heated with coils 33 so that the resulting vapor zone 30 immediately overlying the hydrocarbon is essentially a fluorocarbon-based nonflammable or flammability suppression vapor zone to minimize the possibility of explosion.
• the cleaning fluid mixture may or may not require a surfactant additive to ensure phase homogeneity between the organic hydrocarbon and the fluorocarbon solvents.
• the fluorocarbon which was boiled off would be maintained at a constant concentration in compartment 15 by either returning the vapor condensate back to this compartment and/or pumping fluid from the rinse compartment(s) 20,25 back to this sump through control with a volume or level-sensing transducer (not shown).
• the boiling rinse sump 20 may not be necessary, or it could function purely as a second rinse sump at any intermediate temperature between compartment 15 and compartment 25.
• sump 20 may be heated with heating coils 34 and heating coils
• heating coil 33 may not be necessary. In the two-sump option where sump 15 supplies the fluorocarbon vapor to form the nonflammable blanket 30 for vessel 10, heating coil 33 would be preferred and heating coil
• sump 15 supplies the fluorocarbon vapor to form the nonflammable blanket 30 for vessel 10
• sump 20 may not be necessary and sump 25 would provide a cool liquid rinse immersion prior to bringing the cleaned substrate into the vapor condensing zone 30 for a final pure condensate rinse.
• the rinse sump 20 may contain a saturated solution of the hydrocarbon based cleaning fluid and the
• the fluids are selected so that the hydrocarbon phase separates at some low concentration (i.e., less than 10 mole %) in the fluorocarbon and floats to the top of the more dense fluorocarbon, providing a cascading effect back into the cleaning sump 15.
• the rinse sump(s) 25a or 25b may also in turn cascade pure rinse solvent into sump 20 to maintain its level and also to directionally provide a flow skimming action to sweep the separated organic layer towards the boil sump 15.
• the boil sump 15 contains both hydrocarbon and fluorocarbon based solvents of sufficient immiscibility to form layered cleaning zones 15a and 15b.
• the advantage of this arrangement is that the heating coil 33, which provides the nonflammable vapor blanket for vessel 10, is now immersed in a fiuorocarbon-rich phase which lessens the possibility of accidental fire if the liquid in the sump drops below its intended level.
• the boiling fluorocarbon liquid now provides an agitation action to the top less dense organic hydrocarbon phase to assist in the cleaning performance.
• the fluorocarbon rinse solvent and the hydrocarbon cleaning solvent can be cascaded or pumped back to their respective sumps to ensure that sump liquid volumes are maintained.
• the hydrocarbon cleaning zone 15 may be separated from the rinsing zones 20 and 25 by being provided within separate structures 11 and 12. This configuration is intended to provide the ability to retrofit conventional solvent vapor degreasing or defluxing batch-type equipment such as represented by vessel 12 in Figure 5 with the cleaning process of this invention.
• the carry-over of organic solvent from vessel 1 1 to vessel 12 can be reduced by mechanical devices such as an air knife 37. Nitrogen or any other nonflammable compressed gas may be introduced into the vapor zone overlying the hydrocarbon sump 15 to reduce
• the residual hydrocarbon carried over from cleaning sump 15 may be mechanically separated out as described in Figure 1 and recycled back with a pump 45 (as schematically depicted) in view of the physical separation of the two cleaning zones which would prevent cascading as in the previous embodiments.
• the first rinsing zone is provided with a coupling solvent (such as an alkanol like butanol, or another fluorochemical such as trifluorobenzene, or any other type of hydrocarbon) wherein the fluorocarbon solvent is miscible with the coupling solvent.
• a coupling solvent such as an alkanol like butanol, or another fluorochemical such as trifluorobenzene, or any other type of hydrocarbon
• the fluorocarbon solvent has a lower boiling point than either the organic cleaning solvent or the coupling solvent.
• the fluorocarbon in sump 25 primarily serves the purpose of blanketing the flammable liquids in sumps 15 and 20 with a nonflammable vapor, and the level of liquid in rinse sump 20 which is comprised primarily of coupling solvent is maintained by makeup with fluorocarbon liquid from sump 25.
• the substrate which has been rinsed in coupling solvent sump 20 is either subjected to a final immersion rinse in sumps(s) 25a and/or 25b or is held in the fluorocarbon condensing vapor zone 42 for a final rinse, which can be suitably accomplished since the coupling solvent is miscible with the fluorocarbon solvent.
• the amount of soil on the coupon before and after cleaning was determined with a commercial CO 2 coulometer, which measures to microgram sensitivity the amount of organic residue, expressed in carbon units, on a surface.
• the sample of residue on the coupon is introduced into a combustion furnace via a sample boat, and is combusted in oxygen atmosphere at a temperature of 650°C.
• the resulting CO 2 and other combustion products pass through scrubbers to remove any interfering halogens, sulfur, nitrogen oxides and water.
• the gas then passes to the coulometer cell which contains an indicating solution.
• a (C 9 to C 11 ) methyl ester is used as the organic solvent.
• Spectroscopic characterization indicated a small quantity of a branched component.
• HFC 52-13 is a branched hydrofluorocarbon (C 6 F 13 H) used as the fluorocarbon rinsing agent.
• the methyl ester is effective in removing petroleum based oil from metal coupons at room temperature, but a thin film of the methyl ester solvent remained after the cleaning process. The oil is not able to be cleaned from the surface of the coupon by HFC 52-13.
• a dibasic ester cleaning solvent mixture was prepared in the laboratory by synthesizing the dimethyl esters of adipic acid, succinic acid, and glutaric acid in the proportions of 10 wt%/22 wt%/68 wt%, respectively.
• Soiled coupons were immersed in a mixture of the dibasic esters with HFC-365 (CF 3 CH 2 CF 2 CH 3 ) at 56°C for 30 seconds, followed by a 30 second immersion in HFC-365 at ambient temperature and a 30 second vapor rinse with HFC-365.
• Soiled coupons were immersed in a 50 volume % mixture of polyethylene glycol (MW 200) (a polyether diol) and a methyl ester, and 50 volume % of HFC-365, a hydrofluorocarbon, for 30 seconds at 45-50°C followed by a 30 second immersion in HFC-365 at ambient temperature and a 30 second vapor rinse with HFC-365.
• MW 200 polyethylene glycol
• HFC-365 a hydrofluorocarbon
• FC-72 perfluorocarbons such as FC-72 are very poor solvents for oils, but when blended with hydrochlorocabbons or even hydrochlorofluorocarbons in the vapor or immersion rinse step of this process combined with an organic cleaning step, the dual solvent process produces completely clean coupons which could not be completely cleaned by the individual solvent themselves.

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• Wood Science & Technology (AREA)
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Citations (5)

• 1994
  • 1994-05-27 EP EP94919272A patent/EP0701634A1/en not_active Withdrawn
  • 1994-05-27 WO PCT/US1994/006004 patent/WO1994028196A1/en not_active Application Discontinuation
  • 1994-05-27 CA CA002163351A patent/CA2163351A1/en not_active Abandoned
  • 1994-05-27 AU AU70470/94A patent/AU693453B2/en not_active Ceased
  • 1994-05-27 JP JP7500986A patent/JPH08506615A/ja active Pending
  • 1994-05-27 CN CN94192765A patent/CN1127017A/zh active Pending
• 1995
  • 1995-12-01 KR KR1019950705430A patent/KR960702872A/ko not_active Application Discontinuation

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