Alcohol Ethoxylates

Nomenclature

Abbreviations: AE, alcohol ethoxylates, AEO

Alkyl polyoxyethylene glycols

Ethoxylated fatty alcohols

Monoalkylpolyethylene glycol ethers

Polyoxyethylene alcohols

Polyoxyethylated fatty alcohols

Polyoxyethylenated straight-chain alcohols

Examples:

Coco alcohol + 5EO, this represents the alcohol derived from coconut fatty acid, reacted with five molecules of ethylene oxide.

Description

The main commercial products of alcohol ethoxylates are based on the following alcohols:

Mixed coconut oil fatty acid fractions hydrogenated, C₁₂-C₁₄ chain length

Synthetic straight chain C₁₂-C₁₈, various fractions based on Ziegler alcohols, i.e., even number chain lengths

Synthetic straight chain C₁₂-C_l5, various fractions based on oxo alcohols, i.e., odd and even numbered chain lengths

Natural alcohols, e.g., castor oil

Tallow-derived C₁₆-C₁₈ products with high oleyl content are more fluid than the saturated derivatives

Hardened tallow C₁₆-C₁₈, hydrogenated products with low unsaturation.

The ethoxylation of a primary alcohol gives a different distribution to that

of a nonyl phenol or carboxylate. The result is that free alcohol remains in most ethoxylates when the degree of ethoxylation is not high, thus for the reaction between dodecanol and 3 moles of EO the resulting ethoxylate has the composition shown in Table 1.

In end-blocked non-ionics and low foam alcohol ethoxylates, the terminal OH may be reacted with propylene oxide to give reduced foam, but the degree of biodegradability decreases as the propylene oxide content increases. In addition, the terminal H on the EO or PO chain can be replaced with an alkyl group or the benzyl group. They are used to chemically stabilize the products.

If the end group is bulky, e.g., benzyl, then foam reduction is also obtained.

General properties

1. Solubility:

When the EO content increases beyond 5 moles EO/mole of alcohol, there will be very little difference in solubility between a C₁₂, a C₁₂-C_14, or a C12- C15 alcohol ethoxylate. For the solubility of a C12- C14 alcohol ethoxylate, see Table 2. For the solubility of oleyl and tallow ethoxylates, see Table 3.

2. Cloud point:

Highly branched (2 or 3 methyl) alcohols are significantly more hydrophobic than their more linear counterparts and more EO has to be added to achieve the equivalent cloud point.

3. Chemical stability:

Excellent for acids but the free hydroxyl group is sensitive to concentrated alkali and turns brown in powdered products, Unstable with high pH and oxidizing agents (e.g., hypochlorite bleach)

4. Compatibility with aqueous ions:

Excellent with hard water.

5. Surface active properties:

CMC increases as the EO content increases. For a C₁₂-C₁₄ alcohol mixture, the minimum CMC is at about 0.001- 0.003% at low EO levels, rising to 0.02-0.04% at high (15-20) EO. C8-C18 linear alcohols show similar behavior in that the minimum surface

tension obtainable decreases with decreasing EO content. Lowest surface tension is 29 dyn/cm at 5-7EO, i.e., where AE is nearly insoluble, rising to 40dyn/cm at 15EO. The branched chain alcohols (C₁₀-C₁₂) have a constant surface tension (29-33 dyn/cm); however, while the EO content varies from 5EO to 30EO.

6. Functional properties:

By choosing the appropriate alcohol and the appropriate degree of ethoxylation the alcohol ethoxylates can give the following properties.

Excellent wetting: linear alcohol C₈-C₁₄ with 7 -12EO; for each alcohol, there is a sharp optimum of EO content with the wetting power decreasing rapidly with increasing EO content above the optimum; branched chain alcohol ethoxylates show better wetting than straight chain alcohols of the same molecular weight. Good flash foam but poor foam stability: linear alcohols generally give better foam than branched chain alcohols; most stable foams with C₁₀-C₁₄ alcohols obtained with 8-12EO content; hard water has only a minor effect on flash foam but decreases foam stability.

Excellent dispersing power: optimum alkyl chain and EO content depends upon the material being dispersed but high molecular weight products are better than low molecular weight.

Excellent emulsifying properties: optimum alkyl chain and EO content depends upon material being emulsified.

Excellent detergency: optimum linear alcohol C₁₂-C₁₅ with 6-15EO; Higher alcohols, e.g., C₁₈, show excellent detergency but need higher EO levels (15-20EO).

Note, however that the optimum level of EO depends very much on the temperature.

7. Disadvantages:

Compared to NPEs, AEs contain free alcohol in inappreciable quantities at low levels of EO.

Applications

1. Intermediate for sulfation:

The 2- and 3-mole EO are sulphated for use in detergents and cosmetics.

2. Household products:

Heavy-duty powder detergents, major component of low and medium foam detergents, C₁₂-C₁₄ alcohol + 9EO; heavy-duty liquid detergents, more soluble than LABS for use in high-active heavy-duty liquid detergents which are free or low in phosphates; used with LABS as solubilizer and foam stabilizer, usually C₁₂-C₁₅ + 7-9EO.

3. Industrial detergents:

Metal cleaning, low foam products stable to alkali, e.g., benzyl blocked; machine cleaning of food soils, low foam products, benzyl or propylene oxide tipped.

4. Textiles:

Wide variety of AE used for scouring depending upon the temperature, e.g., C₁₃ + 5EO (HLB 10.5) for low temperature textile scouring; lubricants and antistatic agents in fiber processing, tallow + 20EO, also mineral oil and vegetable oils are used as lubricants with AEs as emulsifiers; emulsifiers as dye carriers (better emulsifiers than corresponding NPEs) and for hydrophobic glycerides in blended fibre lubricants; dyeing assistants for wool/synthetic blends, tallow + 20-40EO; in cotton processing as penetrants, wetting agents and dyeing assistants.

5. Emulsifiers:

For W/O emulsion in mineral oil, paraffin and chlorinated solvents, C₁₂-C_l5 + 3EO; for waxes, fats and oils, C₁₂-C₁₅ + 7-8EO; for solvent emulsifier in dye carriers, C₁₂-C₁₅ + 23EO; Cosmetic, the higher alcohols, oleyl, ceto-stearyl are used as emulsifiers in cosmetics to emulsify oils and fats, a combination of a lower (2-3EO) and a higher (10-20EO) ethoxylate can give O/W and W /O emulsions; the presence of some free alcohol (i.e. oleyl or stearyl alcohol) is not detrimental to odor as would be the lower alcohols, e.g. lauryl alcohol; castor oil + 5EO emulsifiers and dispersing agents to give antifoam properties to chlorinated solvents.

6. Agriculture:

Excellent emulsifiers for pesticide sprays because they are unaffected by hard water and pH changes; used in emulsifiable concentrates, e.g., castor + 30EO; water-soluble emulsifiers used in conjunction with anionics in agricultural herbicides.

7. Paper industry:

Re-wetting agents to improve absorbency, e.g., paper towels; repulping aids for wastepaper.

8. Emulsion polymerization:

Excellent emulsifier for emulsion polymerization due to tolerance to inorganic ions and pH changes.