National Clothesline

rycleaning detergents for hydrocarbon, Stoddard and perchloroethylene solvents are surface active agents or what is chemically called “surfactants,” and they are therefore solvent-soluble.

As with soil, these surfactants are classified as either ionic (electrically charged) or non-ionic (electrically inert). These ionic drycleaning detergents are either anionic or cationic since their

molecules will split into charged particles when dissolved in water.

The charged particles are known as ions; and, when a molecule of an ionic compound splits into two parts in water, one part takes on a positive charge and the other takes on a negative charge.

Detergent molecules can best be explained by dividing them into two parts: a small head and a long tail. The head likes water and hates dry solvent, and it is called “hydrophilic,” therefore, it is water-soluble. The tail end of the detergent molecule hates water, and it is the active or detergent end.

When ionic detergent molecules split up in water, the charge taken on by the long tail, or active end, determines whether the detergent is anionic or cationic. If the tail assumes a negative charge, it is known as an anion, and the detergent is an anionic detergent which is also the basis for the “charge” system of drycleaning due to its almost total solubility in dry solvent. Only the tiny hydrophilic head is not soluble in dry solvent. Water additions can be made in a charge system if certain precautions are made.

If the tail assumes a positive charge, it is known as a cation, and the detergent is a cationic detergent which is the basis of the “injection” system of drycleaning due to its total insolubility in dry solvent. This detergent is usually blended with a small amount of water and is very substantive to fabrics and filter paper. Water additions cannot be made with the cationic detergent blend.

A molecule that does not split in water does not ionize, and detergents that are made up of these molecules are known as non-ionic detergents. What is a molecule? It is a very miniscule particle which retains all the properties of the (detergent) compound. For example: a toothpick has all the properties of the whole tree. Non-ionic detergents have one problem that make them difficult to use: they cannot be titrated for detergent concentration in solvent unless a “tracer” is used.

A tracer is a material that can easily be measured by titration and is usually an addition of anionic surfactant to the non-ionic detergent concentrations. The amount of non-ionic detergent is measured by determining the percentage of anionic detergent contained in the detergent mixture. However, the titration is impossible when an adsorptive-type filter cartridge or tonsil powder with diatomaceous earth is used.

An adsorptive-type filter cartridge will remove anionic detergent but not non-ionic detergent. Also, a non-ionic detergent charge system cannot receive water additions safely as with the anionic detergent charge system since both detergent and solvent are non-ionic. Any added water will form an “emulsion” with free water harmful to garments in the load.

Basic anionic detergents usually contain several kinds of anionic surfactants and may be combined with a non-ionic material. Drycleaning detergent manufacturers spend much time, effort and money to find the right combinations of various materials that produce the most effective cleaning results.

Anionic detergents will form a solution (not milky emulsion unless too much water is added or present) to dissolve water-soluble soil. Small concentrations of water in the solvent/detergent mixture actually cannot be seen in the sight glass, but the water is there without adverse effects on fabric stability. Soil removal is actually increased by concentrations of moisture in solution.

Cationic surfactants have become more widely used in recent years. As stated before, the cationic detergent/water blend will be totally adsorbed onto the fabrics due to its substantive nature. For this reason only small doses (usually one-tenth to one-fifth of an ounce of detergent blend per pound of garments) must be made with the cleaning washer drum set on “batch” mode.

This means that no solvent and its detergent blend will leave the drum for deposit through the filter since the filter medium will adsorb the detergent blend and build up filter pressure quickly. “Milling” the solvent and detergent blend, by pumping from the cylinder, through the metal button trap and back to the cylinder, is acceptable.

After about a three-minute batch, or mill, it is assumed that the detergent blend has completely been adsorbed on the garments, and the solvent is then either sent through the filter for about ten minutes (perchloroethylene solvent) or about 22 minutes (hydrocarbon and Stoddard solvents).

To maintain a good distillation rate, some plants will drain and extract the batch, or mill, to the still after the three minutes. The second bath is with distilled solvent for good solvent conditioning and filtered for the required time. Then the solvent is drained and extracted to a work tank to be used for the next batch, or mill.

Unlike anionics, the cationics act as an emulsion method of removing or loosening water-soluble soil, very much as in pre-spotting with a solvent/detergent/water emulsion. For this reason, best results are obtained by adjusting the solvent flow-rate to 75- to 90-second cylinder drum fill time.

The operator must not use an excessive amount of cationic detergent because the most desirable function of this surfactant is its substantive quality of going to the surface of the fabric, and the excessive amount will leave a poor “hand” to the garments making them too firm and sticky. This gives the advantage of acting as a fabric conditioner and anti-static agent if used properly.

A good distillation rate is essential for good cleaning and maximum effectiveness of all drycleaning detergents. Therefore, a minimum distillation rate of 18 to 20 gallons of working solvent per 100 pounds of garments cleaned is recommended.

The use of adsorptive filter cartridges or tonsil powder with diatomaceous earth will also remove the ionic detergents along with the dyes and soluble oils. Therefore, these filtration systems should only be used with the cationic detergent injection method.

Whether you use the anionic or cationic injection system, the correct amount of detergent is mandatory for insoluble soil removal. This applies critically to perchloroethylene solvent since its surface tension rating is much higher than hydrocarbon or Stoddard solvents, and the detergent will reduce that rating to add the lubricity required for digging out and suspending insoluble soil in addition to increased penetration through the fabrics.

Distilled, or new, solvent with no detergent will flush out the loose insoluble soil, but the ground-in soils will need the power of detergent for easy removal. Distilled, or new solvent will not suspend the insoluble soil once it has been removed; it takes detergent to give the suspension needed.

If water additions are desired, only anionic detergent in proper charge percentages must be used. In this regard, it is required that the system be managed properly to ensure that any make-up solvent, uncharged (with detergent), be charged by adding 1.5 percent to 1.7 percent of anionic detergent.

Usually, a 1.5 percent to 1.7 percent (by volume) detergent charge can be maintained by adding about two ounces of anionic detergent per gallon of solvent added to the system. After adding the detergent to the button trap, or in the drum, run through the filter (non-adsorptive type) for about five minutes to dissolve the detergent into the solvent.

An easy-to-use titration kit is available from your detergent manufacturer at no charge. This should be used by the operator at least once in the morning, or evening, to check the anionic charge in the system before adding more detergent.

Weighing the load is essential to determine the amount of cationic detergent blend to be injected, and it is essential to determine the amount of water “stock solution” (ten parts water mixed with one part spray spotter detergent) to be added, or injected, into the anionic charge system.

Static electricity is greatly reduced when detergent lowers the surface tension of that solvent. Re- deposition of insoluble soil is avoided only by the suspension and lubricating qualities of the drycleaning detergent and the absence of static electricity; new, distilled or conditioned solvent alone will not be effective.

One of the major functions of a drycleaning detergent is its ability to allow water to be introduced into the drycleaning system. An explanation of why this is possible begins with the ionic solution and the molecular solution as described earlier.

This discussion must include a third solution, called “colloidal,” which is composed of ionic detergent molecules dispersed in the drycleaning solvent. When the molecules are held together as a group by various types of ionic attraction (intermolecular) a cluster of detergent molecules act as a single unit and are called “micelles.” The anionic tails are attracted to the cationic heads which hold the moisture.

In other words, micelles and their function as a water carrier in the drycleaning washer is the result of the solvent-soluble tail of detergent dispersed in the solvent while the water is dissolved into the water-loving head.

The more detergent contained in the solvent, the more water-loving heads contained in the solvent; hence, the more water additions we can make safely into the solvent.

The interior of the micelle is a “little ionic island in the non-ionic sea.” It is into these little islands that the water goes. If enough water is added, the center of micelle consists of an extremely tiny water droplet.

This water is dissolved into the detergent molecules. This is the basis of the charge system: Solvent is non-ionic, but the water and detergent are both ionic, therefore, both solvent-soluble stains (non-ionic) and water-soluble stains (ionic) are dissolved.

Water that is dissolved within detergent micelles can dissolve salts, sugars, water-soluble dyes and other water-soluble stains if added in sufficient quantity and provided:

1. Solvent temperature is between 75° F and 80° F.

2. High level of solvent in drum.

3. Fifteen minutes of wash time. Twenty five minutes for hydrocarbon and Stoddard for removal of solvent-soluble soils.

4. Load factor of three pounds per cubic foot of cylinder volume maximum.

5. Low content of non-volatile residue in the solvent.

6. Minimum flow rate of three-fourths gallon of solvent per pound of garments per minute (ideal is 1 gallon of solvent per pound of garments per minute).

7. Solvent is charged 1.5 percent to 1.7 percent with anionic detergent.

Water and solvent relative humidity will be discussed next month.

Note: My spotting video, “The Caplan Method of Stain Removal,” which includes my comprehensive text (edited by Hal Horning) and handy spotting board reference, is available in English, Spanish and Korean (video only). A special disc for South America equipment is also available through Golomb Group (e-mail: dm@golombgroup.com or phone (800) 679-5856). A lecture and demonstration are presented similar to my classes over the years at IFI and SDA schools. This video and text are ideal for training inexperienced spotters as well as a good review for experienced spotters. Digesting, bleaching, oxidized oil stains and caramelized sugar stains are discussed and demonstrated. An article on “Removing Spots in the Cleaning Machine (for perc and petroleum/hydrocarbon) is included on the text book.

Also available from Golomb Group is my video on step-by-step shirt finishing which includes my comprehensive text in loose-leaf form outlining each procedure for single operator and two-operator cabinet shirt unit using a cabinet sleeve press. Proper forming of the collar using heated collar formers is demonstrated. Each lay is demonstrated for top quality and production with very little effort. Attractive detailing and packaging of the hung shirt, padding, steam pressures and timing are all discussed. A unique wash formula for whiter whites and brighter colors and removal of grease and body oils is included in the textbook.