This article was first appeared in the American Drycleaner magazine about the time of the copyright. It has recently been updated.
THE A, B,C’S OF PETROLEUM DRYCLEANING
What is this new solvent we keep hearing about? Isoparaffin? Hydrocarbon? Petroleum? Stoddard? Gas? I guess it depends on when you entered into the industry. This “new” solvent was the very beginning of the drycleaning industry, as we know it. It comes from the ground and is then refined and cleaned up. As time progresses, it keeps getting cleaner and cleaner.
If you have only been in the business for fifty years, it is possible that you have never seen, nor worn clothes that have been cleaned in a petroleum solvent. If that is the case then you have truly missed something. If your landlord has refused to renew your lease; the bank has refused to loan you money or your customers complain about the “toxic” solvent you use then maybe you need to take a look at the facts of this “new” solvent.
Is a high flashpoint solvent the same as Stoddard solvent and hydrocarbon solvent? Yeah, pretty much. The high flash point solvent has some of the properties removed and/or changed that makes it different that a regular Stoddard solvent. It has had a known carcinogen removed (benzene), some odorous compounds removed and the flash point raised to above legal limits, notably 147 degrees F.
The “high flashpoint” solvent is the one we will be talking about in this column. As mentioned earlier, they pretty much all act the same for drycleaning.
The comparison table below will compare some of the characteristics with perchloroethylene and regular petroleum solvent.
Perchlorethylene Petroleum Synthetic Petroleum
Weight per gal. 13.6# 6.7 6.4
Boiling point F. 250 300-400 375-405
Evap. rate. fast moderate moderate
PSI to distill. 35-45 40-60 40-60
Stability. semi-stable stable stable
Corrosivity yes no no
Toxicity. yes minimal minimal
Flash point. none 102-140 147
Degreasing ability. excellent fair fair
Kauri Butanol Value. 89 33 27
PETROLEUM is the oldest of the three solvents in use today for drycleaning clothing. The cost of petroleum solvent is directly related to the price of crude oil. This means that the price of petroleum solvent will probably not be going down in cost. There are many items that can be cleaned in petroleum solvent that would not be drycleanable in perchlorothylene, due to it’s higher degreasing ability. The degreasing ability of any solvent is measured against the degreasing ability of Benzene. This ratio is known as the Kauri Butanol Value, or KBV. The KBV of petroleum is approximately 33. This simply means that petroleum solvent will degrease an object about 1/3 as well as benzene. Petroleum and Synthetic Petroleum solvents are close in their solvency abilities for removing kauri gum, which we more or less equate to oil and grease removal.
The KBV (degreasing ability) of perchloroethylene is almost triple that of petroleum. The normal wash running time for a regular load of clothing is 30 minutes in petroleum or synthetic petroleum solvent. Most petroleum solvent plants have been “grandfathered in” to their existing locations, which means that fire, or other laws, were enacted after the installation of the solvent. Some of the older petroleum solvents had a low flash point, and with inadequate diligence to the cleaning, drying and safety procedures, there have been many fires caused by drycleaning plants. Years ago the various jurisdictions quit permitting new petroleum plants to be built. The fire laws have generally been written to not allow solvents with a flash point of less than 140 degrees F. Kauri Butanol Value (KBV) is not an accurate measurement for oil or grease removal as it was designed by the paint industry with kauri gum and butanol to see how quickly the butanol would dissolve the kauri gum.
SYNTHETIC PETROLEUM (Exxon’s DF-2000 or Chevron’s EcoSolv) is the newest solvent and is an isoparaffin based solvent that has virtually all the characteristics of petroleum solvent. The reason it is gaining in popularity is that it has a flash point of 147 degrees F. and can be installed in almost any building. The cleaning is gentle, it does not bleed dyes like perchloroethylene can and is not considered an environmental threat.
Synthetic petroleum solvent goes through manufacturing steps that regular petroleum solvent does not, as a result synthetic petroleum tends to be more consistent and contains fewer impurities.
There are synthetic petroleum transfer machines that are being built today that allows the operator to clean and extract garments in a washer/extractor then transfer them to a reclaiming tumbler for drying. It is also possible to buy a new petroleum solvent dry-to-dry machine. The advantage of having a washer/extractor and a reclaiming tumbler is that while the tumbler is drying a load of clothing, the washer can be cleaning another load. It is common in the large plants to see a washer/extractor and two reclaiming tumblers.
WELL, WE GOT IT. NOW WHAT?
Since petroleum solvent is not as aggressive towards dyes, acrylic or styrene trim and is less hazardous to Lycra, rubber and elastic, classification is not as rigid as with perc. The classic detergent usage is through the charge method. A detergent charge between 1 and 1.5 % is sufficient for lubrication and suspension of soil. To the solvent there should also be a .5 to .75 % sizing charge. Classification should still be by weight of clothing, then by color, then by soil content. The best cleaning is going to be when the drycleaning machine is run at its true rated capacity. This is usually figured at about 80 % of what the manufacturer of the machine says is its capacity. A sixty pound machine will usually be run at 20% less, 12 pounds, or about 48 to 50 pounds per load. The fullness of the load will help in cleaning and the underloading will aid in drying. Small loads should never be ran due to the lack of cleaning, cost and possibility of streaks and swales in drying.
The solvent, by itself, is mild, non-hazardous and non-toxic. It will stay that way until a contaminant is added to the solvent either through spotting chemicals, homemade secret ingredients, or pollution from the atmosphere that is brought in via dirty clothes.
The single bath, charge system will usually take 24 to 30 minutes to properly clean a full load of clothing. Draining, extraction, drying and cool-down will usually take another 30 or 35 minutes for a total cycle time of about one hour to one hour and ten minutes. There are lesser times if injection, two bath systems are used. Remember, I said PROPERLY cleaning of clothing. Sure, anyone can rinse then bang and hang but that is not what builds business.
Moisture can be used with petroleum solvents but it cannot be abused or overused. It is best to not spray the prespotter but to add it as an emulsion to the wheel before adding the clothing. If this is done then post spotting is rather an anticlimax. Blow a few heavy sweet spots off with the steam gun then practice your true stain removal skills on the stains.
HOW IS THE SOLVENT MAINTAINED?
The petroleum solvents, old or new, are maintained like any other solvent that is used to clean clothes. When the soil is released into the solvent through mechanical action and lubrication it must be disposed of or the soil will go to the nearest medium it can. Unfortunately that is the clothes in the solvent. Insoluble particles are deposited on the filters while the solvent soluble soil (oils and greases) and water soluble soils (perspiration, food residues, and all kinds of stinky stuff) are left suspended in the solvent. These soils either build-up in the system and release the soil to the clothes or the soils are distilled out of the solvent through a vacuum still. The only thing left now to contaminate the solvent (or clothing) are dyes that have been released from the clothes being cleaned. Dyes are very difficult to remove and about the only sure way is to adsorb them with activated carbon that is contained in filter cartridges, bags or through powdered carbon added to a diatomaceous filter system. There are cartridges on the market that contain a activated bentonite clay that will remove the non-volatile residues from the solvent and can maintain them in a reasonable to excellent condition if they are cared for properly. It is not necessary to use an activated carbon fro dye removal when using the bentonite powder. Non-volatile residues are oils and greases from the clothing, drycleaning detergent and sizings or anything else that can get into the solvent, such as paint, oil and grease removers, some compounded ink removers and various other spotting type chemicals.
Odors will build-up in the system and these are normally from water based substances such as perspiration, perfumes, etc. Unfortunately if the solvent is not kept clean there will be a bacteria build-up in the solvent and it will feed on the NVRs, then will turn into a very foul odor that is almost impossible to get rid of. This is not the solvent’s fault. It is always the operator’s fault by not running the system properly and keeping the solvent clean and the machine maintained.
Petroleum solvents are excellent solvents for cleaning clothes. No, they don’t degrease as well as perc but the clothes we get for cleaning today are not as filthy as they were in the 1950’s and 1960’s when perc made such a big difference when it was introduced into the industry. What petroleum solvent can offer is a gentle solvent that does not remove nearly as much dye from garments, does not damage garment components or loosen glues, leaves the clothing with a nice hand, or feel, and is considered non-toxic. It will also keep the landlord and EPA guy off your back. That is enough to switch right there.
There are two bentonite clay products on the market now and are becoming quite popular in order to either reduce or eliminate distillation. Tonsil is a bentonite clay that is distributed by Kelleher Equipment Supply Company in Long Beach, CA. The may be reached at kelleherequipment.com or 1-800-894-1555.
Krystal Klean Powder is a similar product distributed by Jack Godfrey and can be reached at kkpowder.com 817-366-5600 .