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HYDROCARBON FLUID PaF DEVELOPMENT OF ADVANCED z 7 y 2 5

ALTERNATIVES FOR PRECISION AND

METAL CLEANING

AUTHOR: Peter G . Miasek EXXON CHEMICAL CANADA P.O. Box 4029, Station nAn Toronto, Ontario Canada. M5W lK3

Exxon Chemical Company intermediates Department

P.0 Box3272 Houston, Texas 77023-3272

1990 INTERNATIONAL CONFERENCE ON CFC AND HALON ALTERNATIVES

NOVEXBER 27-29, 1990

BALTIMORE, MARYLAND

DFXEIQPMENT OF ADVANCED HYDROCARBON FLUID ALTERNATIVES FOR PRECISION AND

METAL CLEANING

AUTHOR: Peter G. Miasek Exxon Chemical Canada

TORONTO, Ontario. Canada. M5W 1K3 P.O. BOX 4029, Station "A"

(416) 733-5310

ABSTRACT

Exxon Chemical Company has continued an international development effort to produce efficient and safe fluids for precision and metal cleaning. These are designed to replace chlorinated and CFC solvents. Two families of products have been developed, built on hydrocarbon and ester chemistries. These feature good cleaning power, high flash points, l o w vapor pressures, no SARA reportables, low worker toxicity, low odor and easy recycle and disposal.

Data will be presented on actual case histories from industrial users covering cleaning performance, equipment modifications and worker comfort.

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I With the adoption of the Montreal Protocol and, in the USA, the passage of the Clean Air Act, the phase out of methyl chloroform (MC) and CFC-113 is now a certainty. As a result, thousands of users of these solvents in metal cleaning processes will need to find alternative cleaning fluids. Many of these users are reluctant to employ other chlorinated solvents such as trichloroethylene, perchloroethylene, or methylene chloride as these all have lower permissible exposure limits than MC or FC-113, as well as other toxicity concerns.

HCFC solvents will likely be chosen by some users, but will not be a universal solution due to their high cost and the fact that these too will ultimately be phased out.

AS a result, many metal processors are seriously examining non-halogenated alternatives in metal cleaning, as shown in Figure 1.

There are a number of these including no clean options, detergent cleaners, alkaline cleaners and semi aqueous or emulsified cleaners. Except for the no clean option, which of course is most preferable if technically feasible, these alternatives all employ water as part of the cleaning fluid or process.

All of these alternatives have their place and should find niches . as viable cleaners. But Exxonls experience has shown that a

significant number of metal processors will experience difficulties with water-based products (Figure 2). These include poor cleaning action on some types of dirts, corrosion, staining and spotting, and poor penetration or wetting of tightly packed parts. In addition, these products require high amounts of energy to evaporate the water. Finally, there are potential problems with disposal of the spent water phase.

For users with these types of issues, aqueous systems may not be a good alternative.

HYDROCARBON SOLVENT CLEANERS

There is another approach. This approach was used for decades before halogenated solvents came onto the scene. This approach uses hydrocarbon solvents.

Thirty years ago, petroleum hydrocarbon solvents were commonly used in metal cleaning. These were not technologically very advanced solvents - they were basically fractions of petroleum that had been sweetened to kill the sulfur odor. They were called such names as Naphtha, White Spirits, Stoddard Solvent and Mineral Spirits. In metal cleaning, these products were gradually replaced by halogenated hydrocarbons. There were valid technical reasons for this development. Although cleaning power was comparable for the two types, the non flammability of halgenated solvents resulted in process and equipment advantages.

Thus, hydrocarbons disappeared from the mind of the end user, who remained unaware of the improvements in quality and performance J

that were occurring in these 3roducts.

During the following years, the petroleum industry developed new separation and synthetic processes to produce specialty products with features (Figure 3) like narrow boiling ranges, low flammability, virtually free of aromatics, high solvent power, virtually free of odor, and very low surface tension (good surface wetting)

Now with the finding of toxicological and environmental problems with halogenated hydrocarbons, we feel users should give the new generation of hydrocarbons and oxygenated hydrocarbon solvents a fresh look.

The range of possible chemistries available in modern hydrocarbon and oxygenated hydrocarbons is very large, and includes such diverse families as:

0 0 0 0 0 0 0 0 0 0 0

Petroleum fractions Paraffins Cycloparaffins Olefins Diolefins Aromatics Alcohols Ketones Esters Ethers Carboxylic Acids

Exxon Chemical manufactures products in all of these families. And interestingly, many of these chemistries can be used in cleaning and degreasing of metal.

However, based on our understanding of the metal cleaning industry, it is possible to select and develop preferred chemistries as CL and CFC solvent replacements in metal cleaning. The features of such fluids fall into three broad categories - effectiveness, environmental safety and worker safety/comfort, and are described in more detail in Figure 4.

The two families that Exxon has selected as halogenated solvent replacements' in metal cleaning meet these criteria and are typical of what might be expected from modern hydrocarbon or oxygenated hydrocarbon cleaners. They are:

0 ACTREL(l) Fluids - hydrocarbon rich solvent formulations based on paraffin or cycloparaffin structures.

EXXATE (l) Fluids - Aliphatic ester blends. 0

In each case there are families available that differ in flash point, relative cleaning power, drying time, odor and other properties.

Key physical properties of some of the grades are shown in Figure 5 . Detailed data on all eleven of the products are available in our product literature. For comparison, I have included data on two halogenated solvents. The ACTREL and EXXATE products are grouped into three flash point categories:

100 - 139' F 140 - 199' F

200+"F These flash point ranges correspond to the various US Dept. of Transport classes currently in effect, or pending.

A s is typical of higher flash hydrocarbon solvents, these materials are all less volatile than halogenated hydrocarbons. You will see some vapor pressure data later. As a result, the dry times are slower. Our experience shows many industrial processes can tolerate the increase in dry time that corresponds to a change to a fluid with a flash point in the 105-130 F range. For the higher flash grades, processes using drying at elevated temperatures or rinsing with more volatile fluids can be employed. These will be described later.

Some hydrocarbon grades have extremely low odor which can greatly aid worker comfort.

Lastly, let me comment on cleaning power. There is no question that these types of products clean well. Laboratory data are shown in our product literature and indicate that cleaning power with hydrocarbons is as good as with chlorinated solvents. The reason for good cleaning is that the main types of grimes removed in metal cleaning (lubricants, metal working fluids, greases) are composed of hydrocarbon and ester chemistries. And, in cleaning, the old adage "like dissolves like" definitely holds. Another important attribute of these types of products is a low surface tension, giving good surface wetting and penetration of tight areas. There are of course, small performance differences depending on the specific grime. I've listed a relative ranking here for a thick grease. A good description of the various physical chemical processes involved in cleaning, including the importance of surface wetting and solubilization, is given in Ref. (2).

CLEANING PROCESSES

There are numerous ways to utilize hydrocarbon products like the ACTREL or EXXATE fluids in a cleaning process. In a l l cases, properly designed equipment is needed to avoid the risks associated with flammability. Some process options are shown in Figure 6 . These can be combined or modified to suit the particular application. For example, multi-stage processes can be employed to increase the degree of cleanliness.

All processes involve liquid-phase cleaning at temperatures sufficiently below the flash point of the fluid. Ultrasonics or other agitation processes such as immersion spraying can be used to augment cleaning action. Spraying or misting processes, where fine droplets are formed, should be employed only in an inert environment or with equipment otherwise protected from ignition conditions. This is because fine droplets can be ignited at temperatures below bulk fluid flash point.

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Fluids with flash points near 4 0 ' C (104' F) should be operated in unheated equipment, operating at ambient temperatures, A typical process is shown in the Figure. More than one stage can be employed to increase the degree of cleanliness. It will be shown later that this process can be retrofit into existing vapor degreasers. In the ambient temperature process, drying is most commonly done by forced air drying at ambient temperatures.

Another approach is hot cleaning. This can be employed to boost cleaning action. This process is only suitable for higher flash fluids. For systems with good temperature control (independent temperature sensors, cutouts, level indicators, etc.), Exxon Chemical recommends a safety margin of 15' C ( 2 7 ' F) between the fluid flash point and the cleaning temperature. For systems with poorer temperature control, a higher margin should be employed. Again, more than one cleaning stage is possible.

To dry the part following hot cleaning, a number of techniques can be employed. The simplest is to utilize a heated forced air dryer. The dryer should either operate at 15' C below the flash point of the fluid, or sufficient air flow should be provided so that the effluent air composition is well below the Lower Explosive Limit of the system. Alternatively an ambient temperature rinse with a faster evaporating grade can be employed. Finally, some applications require that a thin film of protective material be left on the part for corrosion protection. This can be effected by the last route shown in Figure 6.

There are various cleaning machine manufacturers across the world working on designing cleaning machines using this hot cleaning concept. Contact us if you wish more details.

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Exxon has completed engineering studies on the safe design of hydrocarbon-based cleaning equipment and- additional information can be made available.

One question we are often asked concerns retrofitting or modifying existing degreasing equipment that was using halogenated solvents to safely handle ACTREL or EXXATE fluids. Can this be done? Our experience shows that this is indeed possible.

In Germany, one manufacturer of cleaning equipment, working together with Exxon, has developed specific retrofit guidelines that comply with the Codes in that country. In the USA, our engineers again confirm that retrofitting is possible. The procedure first requires examination by qualified personnel in such areas as process design, operating procedures, electrical compliance and materials compatibility. Following this, investment may be needed in such areas as electrical equipment upgrades, new level controllers, etc.

The bottom line is that either new or revamped equipment will operate safely and effectively when it is properly designed and meets the applicable safety codes requirements for design and operating procedures.

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Let me close this section with two actual case histories where a successful retrofit has been achieved. These were both in Germany. Let me point out that these were machines that end users developed on a quick trial basis just to prove that these products and processes will work. They do not represent the typical level of engineering expertise available in Germany or what would be required in a permanent installation! Cleaning of printing rollers is summarized in Figures 7 and 8, and cleaning of auto components is summarized in Figures 9 and lo.

In conclusion, these examples, and others we could cite, show that modern hydrocarbon and oxygenated hydrocarbon fluids are effective cleaners that can be safely used in a simple process.

R0"TA.L SAFETY

Let me summarize the information on the environmental impact of these types of products. Due to the breadth of available chemistries within the hydrocarbon and oxygenated hydrocarbon families, I will limit my discussion to the ACTREL and EXXATE families described earlier (Figures 11 and 12).

First of course, none of these products have any halogens, so have zero ozone depletion potential.

Secondly, the low vapor pressure makes control of air emissions easy. There are few fugitive emissions and recovery of the material from effluent air used in drying is straightforward. Our experience has shown that condensation is a particularly effective way of recovering vapors, and there are a number of different technologies available. The organic vapor is efficiently condensed into a layer that is less dense than any condensed water. As the ACTREL and EXXATE fluids have minimal miscibility with water, it is an easy matter to re-use this recovered fluid. The air stream leaving the condenser can be recycled to the drying zone in a closed loop, resulting in virtually an emissionless system. Exxon is developing engineering guidelines to assist vendors and users in developing emission control technologies.

There are no components in these fluids that are on the new "Air Toxics" list of the Clean Air Act. I will discuss this later under worker safety.

These fluids will not routinely come into contact with water, except during spills or possibly during the condensation recovery process just mentioned. As mentioned, they have very low water solubility, and are also less dense than water. Thus, during a release to water, they will remain on the surface and evaporate over a period of a few hours or less. That portion which is soluble in water will biodegrade in a matter of days.

In the waste recovery area, the best reclamation technology for these products is usually filtration and distillation. One of the advantages of the low olefin content and narrow distillation range is that the recovery in distillation is high. Although recovery is preferred for environmental and, in some cases, business reasons, disposal of some hydrocarbon may be necessary.

Incineration is a good means of proper disposal of residual solvent. Compared to halogenated solvents, incineration of hydrocarbons requires lower temperature for complete destruction and results in no acid formation in the flue. Segregation of the spent hydrocarbon from chlorinated hydrocarbons, lead and other metals, and water contaminants is essential so that f 9 ~ emissions from the incineration satisfy regulatory guidelines .

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Fuel substitution is another good route of disposal. This option utilizes the waste hydrocarbon in boilers and other furnace equipment. This option is preferable to incineration because the fuel energy of the waste solvent is used beneficially. However the wastes have to be segregated such that no contamination with hplogenated hydrocarbons can occur. Several industrial studies have shown that blending waste solvent with regular fuel causes no noticeable increa in burner maintenance costs or adverse air pollution effects. 7%

Finally, as most of you know, Section 313 Title I11 of SARA (Superfund Amendments and Reauthorization Act) in the USA mandates that a facility must report to EPA all usage of specific "toxic chemicals" above certain minimums. All of the ACTREL and EXXATE products are exempt under Section 313 and do not need to be reported.

WORKER SAFETY AND co" Finally, let's talk about worker safety and comfort, and again I'm limiting my discussions here to the ACTREL and EXXATE grades marketed by our company (Figure 13). . These products have low toxicity and skin irritation. None are suspected carcinogens and none require labelling for any toxicological effects. Recommended exposure limits are as high as 300 ppm.

The USA has just passed a new Clean Air Act. Title 3 of this Act specifies a number of chemicals that are listed as "Air Toxicslt or hazardous air pollutants. There are minimal quantities of Air Toxics in any of the ACTREL or EXXATE fluids.

Some of our ACTREL grades have extremely low odor, which can be very important for worker comfort.

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CONCLUSION

Modern methods for the production of hydrocarbons and oxygenated hydrocarbons have resulted in products which are well suited for use in metal cleaning and degreasing applications. The possibility to utilize selected fluids for cleaning either at ambient or at higher temperatures has opened up a great variety of effective process approaches. These can usually give the same quality of cleaning as halogenated hydrocarbons.

Use of these selected fluids can also result in a process that is safe to both the environment and the worker.

The vendors of cleaning and recovery equipment are essential links in the chain between producers and users of hydrocarbons. They are rapidly developing equipment for hydrocarbon systems. Developments to date have been impressive, and there will be an increasing supply of engineered solutions for an even better utilization of the performance of hydrocarbon and oxygenated hydrocarbon cleaning fluids.

REFERENCES

(l) ACTREL and EXXATE are registered trademarks of Exxon Corporation.

( 2 ) "Reclamation and Reprocessing of Spent Solvents11 A.R. Tarrer, B.A. Donahue, S. Dharmavaram and S . B . Josh i , Noyes Data Corporation, Park Ridge, NJ.

DEVPAPER.PGH

FIGURE 1

NON HALOGENATED ALTERNATIVES IN METAL CLEANING

o NOCLEAN

o AQUEOUS (DETERGENT) CLEANERS

o ALKALJNECLEANERS

o SEMI AQUEOUS OR EMULSIFIED CLEANERS

o HYDROCARBON SOLVENT (NON-AQUEOUS) CLEANERS

FIGURE 2

POTENTIAL PROBJXMS WITH WATER-BASED CLEANING FLUIDS

o POOR CLEANING ON THICK OR CARBONIZED GRIMES

o CORROSION

* _ o SPOTTING/STAINING

o POOR PENETRATION/WETTING OF TIGHTLY PACKED PARTS

o HIGH ENERGY CONSUMPTION

o WATER DISPOSAL

FIGURE 3

NEW DEYELOPMENTS IN HYDROCARBON AND OXYGENATED HYD ROCARBON SOLVENTS

NEW SEPARATION AND SYNTHETIC PROCESSES RESULT IN PRODUCTS WITH:

0

0

0

0

0

0

NARROW BOILING RANGES

LOW FLAMMABILITY

VIRTUALLY FREE OF AROMATICS AND OLEFINS

HIGH SOLVENT POWER

VIRTUALLY FREE OF ODOR

VERY LOW SURFACE TENSION (GOOD WETTING)

FIGURE 4

FEATURES OF MODERN HYDROCARBON SOLVENT CLEANERS

EFFEXTIVE

o EFFICIENT CLEANING FOR WIDE RANGE OF DIRTS o LOW FLAMMABILITY o LOW CORROSIVITY/ATTACK TO METAL AND PLASTIC

ENVIRONMENTAL SAFETY

o NO OZONE DEPLETION POTENTIAL o CONTROLLABLE AIR EMISSIONS (VOC CONTROL) o LOW AQUATIC TOXICITY. BIODEGRADABLE o EASY RECYCLE o NO SARA TITLE I11 COMPONENTS

WORKER COMFORT Q SAFETY

o LOW TOXICITY o NO "AIR TOXICS" o LOW ODOR

L

FIGURE 5

FLUID

PHYSICAL PROPERTIES OF ACTREL AND EXXATE FLUIDS

ACTREL FLUIDS - PARAFFTN AND CYCLOPARAFFIN - RICH FORMULATIONS EXXATE FLUIDS - ALIYL .J ESTER BLENDS

ACTREL 3338L ACTREL 33491;

ACTREL 1960L EXXATE 800

ACTREL 4493L EXXATE 1000

111-TRICHLOROETHANE PERCHLOROETHYLENE

W E P T . C (F) b(CLosn, CUP)

40 (104) 53 (127)

’ 61 (141) 77 (171)

93 (200) 100 (212)

BOILING POINT C ( F)

74 (165) 121 (250)

DRYING TIME, ROOM TEMP. MINS

5.1 17.8

42 58

>200 >200

0.2 1.2

ODOR

VERY LOW VERY LOW

SWEET FRUITY

VERY LOW SLIGHT

STRONG STRONG

RELATIVE CLEANING

POWER (GREASE)

GOOD GOOD

HIGHER HIGHEST

GOOD HIGHEST

HIGHER HIGHEST

FIGURE 6 CLEANING PROCESSES WITH ACTREL OR EXXA'IE FLUIDS

AMBIENT TEMPERATURE CLEANING

I CLEAN DRY I CLEANING PARTS FOR

I Grades) I I I I TREATMENT

> DIRTY ---+ I Immersion/Hosing I--------- > I DRYING I - - - - - - - PARTS I (Fast Evaporating I I----- > I Air Drying I FURTHER

l+ STAGES I I

I RINSE I

I Grades) I

I Ambient Temp. I I (Fast Evaporating I

HOT CLEANING I I

I CLEANING I I I Elevated Temp. I I I DRYING AT I CLEAN DRY

DIRTY--+( Immersion/Hosing I------- I---> I ELEVATED TEMP I------- > PARTS FOR PARTS I (Slow Evaporating1 I I Air Drying I FURTHER

I Grades) I I I I TREATMENT 1+ STAGES I

I I CLEAN PARTS

> FOR TEMPORARY PROTECTION

I FILM REDUCTION I ---> I Air IlDryingIl I -------

FIGURE 7

CLEANING OF LARGE PRINTING ROLLERS

METALLURGY : HIGH GRADE ALLOY GRIME : POLISHING PASTES, CORROSION INHIBITORS FOLLOWING STEP: CHROME PLATING

PREVIOUS DEGREAS ING P ROCESS

o VAPOR DEGREASING WITH TRICHLOROETHYLENE o AIR SUCTION AT RIM OF DEGREASER o OPERATOR COMPLAINTS (HEADACHES, IRRITATION)

RETROFIT DEGREASING PROCESS

o LIQUID PHASE DEGREASING WITH ACTREL 3338L. LIQUID

o NO HEATING OR COOLING

o COST OF RETROFIT $6000 (US)

PUMPAROUND TO ENSURE MECHANICAL ACTION

o CLEANING TIME - 2 MINUTES, FOLLOWED BY RINSE AND DRAIN

OPERATING CHARACTERISTICS

o AIR EMISSIONS 4LB/HR [NO COVER] o UP TO 20% GRIME LOADING IN FLUID BEFORE REPLACEMENT o GREATER OPERATOR COMFORT

FIGURE 8

CLEANING OF LARGE PRINTING ROT.T.EILC

PICTURE 1 - RETROFITTED DEGREASER IN OPERATION WITH ACTREL FLUID

PICTURE 2 - RINSE STEP

PICTURE 3 - ROLLERS COVERED WITH POLISHING PASTE

PICTURE 4 - CLEAN ROLLERS

FIGURE 9

CLEANING OF AUTO COMPONENTS

METALLURGY STEEL GRIME : DRAWING AND STAMPING FLUIDS AND GREASES

PREVIOUS DEGREAS ING PROCESS

o 4 STAGE IMMERSION DEGREASING WITH PERCHLOROETHYLENE o BASKETS LOWERED, LIFTED AND ROTATED o FORCED AIR DRYING

RETROFIT DEGREASING PROCESS

0

0

0

0

0

0

0

2 STAGE IMMERSION DEGREASING AT AMBIENT TEMPERATURE WITH FLUID SIMILAR TO ACTREL 3349L MECHANICAL ACTION PROVIDED BY BASKET MOVEMENT OPTIONAL, LAST STAGE CONTAINING CORROSION PROTECTION FLUID CLEANING TIME - 3 MINUTES PER STAGE BASKET ROTATION TO IMPROVE DRAINING FORCED AIR DRYING - EITHER ROOM TEMPERATURE OR AT 32 C COST OF RETROFIT $10,000 (US)

OPERATING CHARACTERISTICS

o FLUID LIFE - 3 WEEKS BEFORE SPENT

FIGURE 10

CLEANING OF LARGE PRINTING ROIXERS

PICTURE 1 - FOUR STAGE IMMERSION DEGREASING UNIT, DESIGNED FOR PERCHLOROETHYLENE

PICTURE 2 - SAME EQUIPMENT, DIFFERENT ANGLE

PICTURE 3 - INSIDE THE EQUIPMENT. OF BASKET WITH DIRTY PARTS. FLUID.

CONVEYER SYSTEM READY FOR UPTAKE BATH FILLED WITH ACTREL

PICTURE 4 - INSIDE THE EQUIPMENT, CHAMBER 1. BASKET ROTATING AND MOVING UP/DOWN IN ACTREL FLUID.

PICTURE 5 - INSIDE THE EQUIPMENT. BASKET ROTATING OVER CHAMBER 1 TO REMOVE EXCESS ACTREL FLUID.

PICTURE 6 - SIMILAR TO PICTURE 4, CHAMBER 2

PICTURE 7 SIMILAR TO PICTURE 5, CHAMBER 2

PICTURE 8 -

PICTURE 9 - SAME PARTS AFTER DEGREASING IN ACTREL FLUID AND DRYING.

BASKET FILLED WITH DIRTY PARTS PRIOR TO CLEANING

FIGURE 11

ENVIR0"TAL IMPACTS OF ACTREL AND EXXATE FLUIDS

AIR IMPACTS

o NO OZONE DEPLETION POTENTIAL

o LOW VAPOR PRESSURES AID IN VOC CONTROL "Hg AT 20 C

CFC-113 270 1 11 -TCE 100 ACTREL/EXXATE FLUIDS 0.03 - 1.0

ENABLES USE OF CONDENSATION FOR RECOVERY AND RE-USE.

o NO SIGNIFICANT LEVELS OF "AIR TOXICS" COMPONENTS

FIGURE 12

ENVIRONMENTAL IMPACTS OF ACTREL AND EXXATE FLUIDS

WATER IMPACTS

o SAFE'FOR AQUATIC ENVIRONMENT - LOW WATER SOLUBILITY - LOWER DENSITY THAN WATER - BIODEGRADABLE

W A S T E IMPACTS

o FILTERABLE

o RECYCLABLE BY DISTILLATION - LOW OLEFIN CONTENT MINIMIZES CRACKING - NARROW DISTILLATION RANGE

o DISPOSAL BY INCINERATION OR FUEL SUBSTITUTION

REPORTING IMPACTS

o NO SARA TITLE I11 SECTION 313 REPORTABLES - AROMATICS LEVELS BELOW "DE MINIMUS" LIMIT

FIGURE 13

WORKER SAFETY AND COMFORT WITH ACTREL AND EXXATE PRODUCTS

o LOW TOXICITY AND SKIN IRRITATION - NOT SUSPECT CARCINOGENS - NO LABELLING OR CLASSIFYING FOR ACUTE, SUBCHRONIC OR

CHRONIC TOXICOLOGICAL EFFECTS

o NO SIGNIFICANT LEVELS OF "AIR TOXICS" COMPONENTS

o VERY LOW ODOR FLUIDS AVAILABLE

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