Introduction

EMULSION CLEANING is an industrial cleaning process that uses an organic solvent as the main active agent. The solvent is usually a hydrocarbon of distilled petroleum dispersed in water. The emulsion, which alone is potentially volatile, is suspended in a nonvolatile aqueous vehicle. Most emulsion cleaners include emulsifying agents, and some are aided by surfactants. Emulsion cleaners are generally used in situations where alkaline or acid cleaners are not applicable.

Emulsion means tiny droplets dispersed in large droplets. An emulsion is simply a colloidal suspension of one liquid into another immiscible liquid. (Immiscible means the liquids will not mix.) The oil-in-water emulsion has tiny droplets of an organic (hydrocarbon) solvent dispersed throughout a water solution. This is generally the type used in emulsion cleaning. The other is water-in-oil (natural petroleum), which has tiny droplets of a water solution dispersed throughout an oil. The oil-in-water type can easily be washed off with water and light detergent. The water-in-oil type leaves a greasy film that is much more difficult to remove.

The hydrocarbon can be distilled from any of any of different petroleum products, such as naphtha, kerosine, benzene, carbon tetrachloride, or other chlorinated solvents, including 1,1,1-trichloroethane. Most of these are no longer used because they are flammable and potentially carcinogenic and have been identified as causes of ozone depletion. Most emulsions are now based on a "mineral spirits" derivative, a hydrocarbon mixture with a relatively high boiling point (93 to 150 °C, or 200 to 300 °F). Compositions, operating temperatures, and production applications for emulsion cleaners are summarized in Tables 1 and 2.

Table 1 Compositions and operating temperatures for emulsion concentrates

Maximum safe temperature depends on the flash point of the hydrocarbon (petroleum) solvent used as the major component

Table 1 Compositions and operating temperatures for emulsion concentrates

Maximum safe temperature depends on the flash point of the hydrocarbon (petroleum) solvent used as the major component

Component

Composition, parts by volume

Stable00

Unstable(b)

Diphase(c)

Petroleum solvent(d)

250-300

350-400

250-300

Soaps(e)

10-15

15-25

None

Petroleum (or mahogany) sulfonates®

10-15

None

1-5

Nonionic surface-active agents'8"1

5-10

None

1-5

Glycols, glycol ethers®

1-5

1-5

1-5

Aromatics®

5-10

25-50

5-10

Water®

5-10

None

None

(a) Operating temperature range: 4 to 66 °C (40 to 150 °F).

(b) Operating temperature range: 4 to 66 °C (40 to 150 °F).

(c) Operating temperature range: 10 to 82 °C (50 to 180 °F).

(d) Two frequently used solvents are deodorized kerosine and mineral seal oil.

(e) Most soaps are based on rosin or other short-chain fatty acids, saponified with organic amines or potassium hydroxide.

(f) Low molecular weight petroleum sulfonates (mahogany sulfonates) are used for good emulsification plus some rust protection. High molecular weight sulfonates, with or without alkaline-earth sulfonates, offer good rust inhibition and fair emulsification.

(g) Increased content improves stability in hard water, but increases cost.

(h) Glycols and glycol ethers are used in amounts necessary to act as couplers in stable and unstable emulsions. These agents are frequently used with diphase and detergent cleaners to provide special cosolvency of unique or unusual soils.

(i) Aromatic solvents are used to provide cosolvency for special or unique soils. They also serve to inhibit odor-causing or rancidifying bacteria.

(j) Water or fatty acids, or both, are used to adjust the clarity and the stability of emulsion concentrate, particularly those which are stable or unstable.

Table 2 Production applications of emulsion cleaning

Data represent practices reported by a number of plants

Table 2 Production applications of emulsion cleaning

Part

Soils removed

Cleaning cycles

Cleaning, time, min

Subsequent operations

Stable emulsion, dip cleaning

Cast iron parts and machined parts

Machining oil, chips

Alkaline clean, emulsion clean

1

Storage

Stable emulsion, spray cleaning

Aluminum and brass carburetor parts

Machining oil, shop dirt

Clean, blow off00

1

Assembly, storage

Aluminum and brass

Dirt, machining oil

Clean, blow off

2

Assembly, storage

Aluminum cabinets

Machining oil, chips

Clean(b)

1

Assembly, storage

Aluminum housing (automatic transmission)

Alkali

Alkaline clean, emulsion clean(c)

1

Assembly, storage

Automobile wheel assembly, 0.103 m2 (160 in.2)

Drawing compound, chips

Clean, no rinse

1

Assembly, storage

Brass valves

Machining oil

Clean, blow off

2

Assembly, storage

Cast iron motor blocks

Machining oil, chips

Clean, no rinse

2

Assembly, storage

Cast iron motor heads

Machining oil, chips

Clean, no rinse

1

Assembly, storage

Retainer plate, 0.01 m2 (16 in.2)

Shop dirt, drawing compound

Clean

1

Assembly, storage

Steel rings, 100 mm (4 in.) diam

Machining oil

Clean, no rinse

1

Assembly, storage

Steel sinks

Drawing compound, oil

Clean

4

Alkaline soak, then enamel

Tractor parts

Machining oil, dirt

Clean, blow off

1

Wash, then paint

Valves (steel and brass)

Machining oil

Clean, blow off

1

Assembly, storage

Washing machine tubs

Drawing compound

Clean, no rinse

3

Alkaline soak, then paint

Unstable emulsion, spray cleaning

Brake assembly, 0.01 m2 (20 in.2)

Shop dirt, chips

Clean, no rinse

1

Assembly, storage

Brake plates, 200 mm (8 in.) diam

Machining oil, chips

Clean, no rinse

1

Assembly, storage

Brake cases, 100 by 100 mm (4 by 4 in.)

Drawing compound

Clean, blow off

2

Assembly, storage

Diphase emulsion, dip cleaning

Brass or zinc die castings

Buffing dirt

Soak, spray, electroclean,

4

Wash, then plate

acid pickle

(a) Emulsion does not plug holes of the needle valves and does not interfere with subsequent gaging operations.

(a) Emulsion does not plug holes of the needle valves and does not interfere with subsequent gaging operations.

(b) Emulsion does not spot or dull aluminum.

(c) Emulsion furnishes lubricity for interlocking gear parts.

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