Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/005—Preliminary treatment of scrap
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
  • B08B7/0064—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by temperature changes
  • B08B7/0071—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by temperature changes by heating
  • B08B7/0078—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by temperature changes by heating in a fluidized bed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto
  • B08B9/08—Cleaning containers, e.g. tanks
  • B08B9/20—Cleaning containers, e.g. tanks by using apparatus into or on to which containers, e.g. bottles, jars, cans are brought
  • B08B9/38—Cleaning containers, e.g. tanks by using apparatus into or on to which containers, e.g. bottles, jars, cans are brought the apparatus cleaning by using scrapers, chains, grains of shot, sand or other abrasive means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B44—DECORATIVE ARTS
  • B44D—PAINTING OR ARTISTIC DRAWING, NOT OTHERWISE PROVIDED FOR; PRESERVING PAINTINGS; SURFACE TREATMENT TO OBTAIN SPECIAL ARTISTIC SURFACE EFFECTS OR FINISHES
  • B44D3/00—Accessories or implements for use in connection with painting or artistic drawing, not otherwise provided for; Methods or devices for colour determination, selection, or synthesis, e.g. use of colour tables
  • B44D3/16—Implements or apparatus for removing dry paint from surfaces, e.g. by scraping, by burning
  • B44D3/166—Implements or apparatus for removing dry paint from surfaces, e.g. by scraping, by burning by heating, e.g. by burning
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N1/00—Microorganisms, e.g. protozoa; Compositions thereof; Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
  • C12N1/14—Fungi; Culture media therefor
  • C12N1/145—Fungal isolates
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P1/00—Preparation of compounds or compositions, not provided for in groups C12P3/00 - C12P39/00, by using microorganisms or enzymes
  • C12P1/02—Preparation of compounds or compositions, not provided for in groups C12P3/00 - C12P39/00, by using microorganisms or enzymes by using fungi
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B2220/00—Type of materials or objects being removed
  • B08B2220/04—Polymers
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12R—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES C12C - C12Q, RELATING TO MICROORGANISMS
  • C12R2001/00—Microorganisms ; Processes using microorganisms
  • C12R2001/645—Fungi ; Processes using fungi
  • C12R2001/80—Penicillium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• This invention relates to novel methods for removing paint, lacquers and other coatings from metal and alloy materials in particular metallic cans.
• Aluminium containers, and in particular cans for drinks such as beer, soft drinks and food products are the most common metallic containers presently in use which are desirably recycled.
• Most technologies for the removal of coatings such as lacquer and paints from such cans are generally thermal involving incineration of the coating prior to remelting and recovery of the metal.
• Such thermal delacquering steps to remove the coating occur at high temperatures of approximately 536°C and are thus energy inefficient, and produce gases which have detrimental environmental effects.
• D.L. Stewart, Jr., and J.H.L. van Linden "Measurement of Residual Carbon on Used Beverage Containers To Monitor Delacquering
• This patent discloses the process of contacting coated metallic beverage containers with bacteria capable of removing such coatings, where the bacteria are applied in admixture with a nutrient medium capable of sustaining viability of the bacteria, and contacting said mixture for a sufficient amount of time to allow the bacteria to remove the coating from the metallic surface.
• a method of removing a coating from a coated metal or alloy material involving a two stage process comprising initial pre-treatment of the container to alter the structure of the coating and/or make it more amenable to biostripping, followed by the step of biostripping.
• the first step to alter the structure of the coating and to make it more amenable to biostripping involves thermal treatment.
• the thermal pre-treatment may for example be carried out at 250°C to 300°C for periods of up to one hour.
• the second step of biostripping is preferably carried out by bacteria capable of removing said coating.
• the invention also provides for enriched cultures of living organisms or bacteria capable of degrading coatings.
• the enriched cultures can be used to provide pure cultures of individual bacterial strains, using well-known bacteriological methods.
• the bacteria ATCC 53922 first described in PCT/US90/04938 can be used. It will also be understood that variants of any of the above- identified bacteria can be used as well as other life forms containing all or part of the DNA that encodes for the protein or the ability to perform the biodegradative function.
• Most preferably the nutrient medium capable of maintaining said bacteria also helps in the removal of said coating.
• the protein or agent per se capable of performing this degradative function isolated in substantially pure form from cultures may be used.
• a method for isolating organisms or enriching for organisms useful in degrading the carbon based coatings comprising the steps of selection of bacteria capable of growth utilising said coating, said bacteria originating from a source comprising coatings in the presence of essential elements.
• the method of the invention is used to isolate organisms capable of rapidly degrading the more difficult to degrade "green" coloured coatings at a high pH, most preferably at a pH of 8.5.
• the process of removing the coating may also be enhanced by subjecting the coated metal or alloy material to further processing including jet spray action, ultra sound, abrasive treatment or detergent.
• the item may then be processed for recovery or recycling of the metal.
• the item is shredded.
• the invention also relates to products resulting from the above described processes.
• a method of removing a coating from a coated metal or alloy material including the steps of:
• step (i) initial heat treatment of the coated metal or alloy material; (ii) abrasive treatment of the heat treated coated metal or alloy material in step (i) using as the abrasive a similar heat treated surface and/or an unheated and/or uncoated like metal or alloy material; and (iii) agitation of the heat treated and abraded coating with a fluid to enhance the stripping of the paint or lacquer or coating from the metallic or alloy surface of step (ii) .
• the coated metallic or alloy material to be treated is shredded before heat treatment.
• the item may be shredded such that 60-70% of the shredded material passes through a 19 mm screen.
• the abrasive treatment step (ii) and the solution agitation step (iii) are performed simultaneously in a rolling reactor.
• the fluid used in the agitation is water.
• the abrasion and agitation step may be for example carried out for a period of up to four hours.
• the abrasive treatment step (ii) occurs in a rolling reactor in air and the paint, lacquer or coating of the metal or alloy material is removed in step (iii) by jet spray action with a fluid such as water and/or air.
• the thermal pre-treatment step (i) depends on a trade-off between temperature and time.
• the thermal pre-treatment is above 100°C since we have found that thermal pre-treatment below this temperature does not degrade the organic coatings. More preferably the thermal pre-treatment is between 120°C and below 536°C, which latter temperature is a typical temperature used in thermal delacquering. Even more preferably the temperature is between 200° and 400°C.
• the thermal pre-treatment is performed in a rotary kiln although other devices may be used such as for example a fluidised bed reactor or conveyor drier.
• the stripped paint, lacquer or coating and/or fluid used to remove the coating may be treated with organisms such as bacteria, capable of degrading the coating before disposal by conventional means.
• organisms such as bacteria
• the biodegradative function may be performed with the bacteria capable of removing or stripping said coating as described in one of the aspects of the invention above.
• Figure 1 shows photographs of flasks with can material and other material incubated with microbial cultures from different sources.
• Figures 2a and 2b are photographs showing the difference in susceptibility to biostripping of a variety of can material.
• Figure 3a shows the temperature profile in the rotary kiln used in the thermal pre-treatment step of the water abrade method of examples 9 and 10.
• Figure 3b shows the effect of varying pre-treatment temperature on the percent carbon stripped in a 200 litre rolling reactor.
• Figure 4 shows a comparison of carbon levels obtained after thermal treatment alone and thermal treatment with water abrade. The bars represent standard error of the mean.
• Example 1 Biodegradation Of Lacquer From VB And Coke Cans A standard can fragment has been chosen. This consists of a 15 mm diameter button punched from an unused VB can body.
• buttons 50 were added to an orbital shaker flask, bacteria were added and the system incubated at 28°C. Samples of button were removed periodically. Little degradation of the coating was observed after 18 days. At this point 10 coke can fragments were placed in the flask, and allowed to incubate for 7 days. Considerable degradation was noted of the coating on the coke can. It is clear that the different coloured fragments differ in their susceptibility with respect to microbial attack. However biostripping can not be accomplished in a commercially useful imeframe.
• model coatings were prepared by curing paints, lacquers and varnishes onto conical flasks under simulated process conditions.
• Standard microbial growth medium 100 mL was added to 5 flasks containing each coating either from inside the can (IC), outside the can lid (OCL) or inside the can lid (ICL) .
• IC inside the can
• OCL outside the can lid
• ICL inside the can lid
• biocide sodium azide ⁇ 0.1 % w/v
• Standard can fragments consist of V ⁇ lids, and the mass is such that acceptable variation is achieved with one fragment.
• Example 6 Degradation Rate improved by Pre-treatment
• Initial thermal treatment 250°C, 1 hour was carried out, followed by biostripping.
• This two stage process was found to strip green material in a total time of 5.5 hours, compared to approximately two weeks without thermal pre-treatment.
• the temperature and time regime used was much less than thermal processing alone, which is typically greater than 550°C, resulting in less off gas production and little aluminium oxidation.
• the heating step in the two stage process of the present invention appears to alter the structure of the lacquers and varnishes, making them more amenable to biostripping, the residual carbon content being less than 0.01% carbon. This may or may not be as a result of thermal destruction of inhibitors to the growth of the bacteria.
• the two stage process does not appear to be as sensitive to ink pigment which is the case in biostripping alone.
• the net result is a lower dross production, resulting in a decreased waste disposal problem and an increased level of recovery of saleable metal.
• Heat treatment 250°C for 1 hr resulted in total stripping in 2 days.
• the heat treatment resulted in some loss of carbon (1.4% to 0.6%) with the remainder removed at a rate of 0.3% C/day.
• Repeat tests were carried out with both Coke buttons and VB buttons.
• the stripping rate measured for coke buttons was found to be 0.07%C/hr (1.6%C/day). This rate, along with the initial loss of carbon in the furnace (1.4% - 0.8%) resulted in almost complete stripping in 8 hrs, and total stripping within 24 hrs.
• Thermal pre-treatment darkens both the varnish on the can exterior, and the lacquer on the interior.
• the exterior material is removed rapidly after this treatment, with the lacquer removal appearing to be the rate limiting step.
• coke cans and VB cans were heat treated for 1 hr at 300°C prior to further treatment in the following solutions: (1) Distilled water (sterile)
• a 20 L reactor (working column 15 L) was established at pH 8.5 and 5.0 g/L yeast extract. This is a stirred tank system, containing 2 kg of can fragments. These were biostripped in batches to generate material for remelt testwork. Metal was added into a 5 kg molten heel of aluminium with mixing. The dross was allowed to float to the surface, and recovered. The dross make was expressed as % of metal added that was recovered as dross. The data is shown in Table 3. This shows that the biostripped material has a lower dross make than thermally delacquered or untreated cans.
• a rotary kiln 0.6 m in diameter and 10.7 m long was operated with a countercurrent flow of hot gases.
• a typical kiln temperature profile is shown in Figure 3a.
• a series of trials was performed in the kiln at varying operating temperatures ranging from 340°C to 400°C at the gas burner end, ie. the product end.
• Used beverage containers (UBC) were shredded in a hammer mill to a sizing of 70% passing through a 19 mm screen and fed into the kiln.
• the residence time of the cans in the kiln was about 14 minutes. Heat treated UBC could be produced at a rate of 0.5-1 tonne per hour.
• a 0.5 tonne per day pilot plant was constructed to treat the 15 tonnes of thermally pre-treated UBC material generated in the rotary kiln in example 9 above.
• the dimensions of the rolling stripping reactor were 0.75 m in diameter by 3 m long.
• the rolling reactor rotated at the speed of 9.5 rpm, and was fed continuously at a rate of approximately 20 kg per hour of pre-treated cans.
• the reactor had an inventory of approximately 85 kg of cans and 300 litres of water. Can residence time was 4 hours.
• Stripped cans were washed in the integrated trommel with fresh water.

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Cited By (3)

Citations (3)

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• 1994
  • 1994-07-15 EP EP94921535A patent/EP0715549A1/en not_active Withdrawn
  • 1994-07-15 ZA ZA945173A patent/ZA945173B/xx unknown
  • 1994-07-15 JP JP7504213A patent/JPH09500420A/ja not_active Expired - Lifetime
  • 1994-07-15 WO PCT/AU1994/000399 patent/WO1995002471A1/en not_active Application Discontinuation
  • 1994-07-15 CA CA 2166864 patent/CA2166864A1/en not_active Abandoned
  • 1994-07-15 KR KR1019960700205A patent/KR960703686A/ko not_active Withdrawn
  • 1994-07-15 NZ NZ268852A patent/NZ268852A/en unknown
  • 1994-09-08 TW TW83108296A patent/TW278054B/zh active

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