Use of High-Active Alpha Olefin Sulfonates in Laundry Powders

Kirk H. Raney*, Paul G. Shpakoff, and Deborah K. Passwater

Shell Chemical Company, Houston, Texas

ABSTRACT: Alpha olefin sulfonates (AOS) have been used suc- TABLE 1
cessfully for many years in laundry and personal-care products Effects of Alpha Olefin (AO) Process on AO Composition
throughout Asia. Among their documented positive attributes are and Alpha Olefin Sulfonate (AOS) Properties
good cleaning and high foaming in both soft and hard water, AO process (C14/16/18)
rapid biodegradability, and good skin mildness. AOS has com- Component SHOPa Zieglera Mod. Zieglera
monly been marketed as approximately 40%-active aqueous so- Normal AO 95 91 72
lutions. However, with the increased importance of compact Branched olefins 3 7 23
powder detergents produced by processes other than spray dry- Internal olefin 2 1 5
ing, high-active forms of AOS including 70%-active pastes and Paraffins 0.1 0.3 0.4
Di-olefins <0.05 <0.05 <0.05
90+%-active powders are now being utilized for that product
AOS color + + −
sector. In this regard, the rheological properties of non-Newton-
AOS yield + + +
ian AOS and AOS/additive pastes at relevant process tempera- Detergency + + −
tures were measured and found potentially suitable for agglom- Flowability + + −
eration processes. Also, the relationship of AOS powder particle a
For production processes, see Reference 3.
size to surfactant solubility at various wash conditions was ex-
amined to allow determination of the optimal size for both de-
detailed description of the three AO production processes
tergency and processing of laundry powders. Both paste rheol-
ogy and powder morphology are critical factors for the success-
may be found elsewhere (3).
ful use of high-active AOS in compact powder detergents. The sodium salts of AOS have been used for many years
JSD 1, 361–369 (1998). as anionic surfactants in a variety of industrial, personal-
care, and household-cleaning applications. Beneficial at-
KEY WORDS: Alpha olefin sulfonate, detergent, powder, sur- tributes of AOS include good cleaning and foaming prop-
factant. erties in both soft and hard water, mildness to skin, and
rapid biodegradability. Household applications include
laundry and dish detergents, and personal-care applica-
Alpha olefin sulfonates (AOS) are obtained by direct sul- tions include shampoos and liquid hand soaps. In Asia,
fonation of alpha olefins (AO) of varying chain lengths to particularly Japan and Korea, AOS has commonly been
form complex mixtures of alkene and hydroxyalkane sul- used in laundry powders. For production of low-density
fonate isomers. Several references describe the process powders in spray towers, 40%-active aqueous solutions are
chemistry for AOS production (1,2). Purity of the commer- suitable for use. However, with the increasing market
cial AO feedstock is critical for obtaining high-quality share of compact powder detergents, new high-active
AOS. For example, trace impurities such as di-olefins can forms of AOS which can be utilized in nontower processes
lead to color formation during the sulfonation process. are being commercialized. High-active AOS also provides
Also, high levels of paraffins lower the yield of active sur- lower shipping and storage costs relative to those of con-
factant. Of particular importance for AOS used in powder ventional aqueous solutions.
detergent formulations, high levels of branched and inter- Previous studies have determined the optimal average
nal olefins lead to reduced detergency and powder formu- AOS chain length for use in a variety of applications (2,4).
lations with reduced flowability (2). Table 1 shows a com- For a phosphate-built powder detergent, optimal sebum
parison of olefin compositions obtained from three differ- removal from both cotton and 65:35 polyester/cotton at
ent ethylene-based olefin production processes and their 50°C is obtained using AOS having 16 to 18 carbon atoms.
positive and negative attributes when used as feedstock These results, which were obtained using radiotracer de-
for AOS production. The advantages of using feedstocks tergency methods that measure absolute soil removal lev-
containing high levels of normal AO are clearly evident. A els, are summarized in Figures 1 and 2 (4). The cleaning
performance of C16 AOS with these soil/fabric combina-
*To whom correspondence should be addressed at Shell Chemical
Company, Westhollow Technology Center, P.O. Box 1380, Houston, tions is clearly superior to that of C12 linear alkylbenzene
TX 77251. sulfonate (C12 LAS) in these model formulations, particu-
E-mail: khraney@shellus.com larly in hard water.

Copyright © 1998 by AOCS Press Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998) 361
362 K.H. RANEY ET AL.

TABLE 2
Typical Carbon Number Distributions of Commercial AOSa
Carbon number (wt%)
Surfactant 14 16 18
AOS 1416 65 35 —
AOS 1418 15 50 35
AOS 1618 — 55 45
a
For abbreviation see Table 1.

FIG. 1. Effect of surfactant structure on sebum detergency: 100% cot-

ton; 50°C; 1.5 g powder detergent/L; water hardness, cross-hatched bar,
50 ppm, and open bar, 300 ppm. AOS, alpha olefin sulfonate. From
Reference 4.

Commercial AO used in the production of AOS are typ-

ically not single-cut materials like those shown in Figures
1 and 2. Given in Table 2 are typical carbon number distri-
butions for commercial AOS products. As will be dis-
cussed in a later section, AOS 1416 is more soluble in water FIG. 3. Effect of surfactant on flash foaming; 150 ppm hardness; 28°C;
than the other grades and is typically used in liquid formu- 1.5 g powder formulation/L. AE, alcohol ethoxylate; LAS, linear alkyl-
lations. AOS 1418 has an average carbon number of 16 and benzene sulfonate; AES, alcohol ethoxysulfate. For other abbreviations
is therefore optimal for use in powder detergents. AOS see Figure 1. Open bar, 4 min; cross-hatched bar, 8 min; horizontally
lined bar, 12 min.
1618 is the least water-soluble grade and has been used as
a foaming agent in high-temperature industrial applica-
tions such as steam-enhanced oil recovery (1). ethoxylate (AE) based on a C12 to C15 hydrophobe, C13
In addition to good cleaning properties, high foaming is LAS, and alcohol ethoxysulfate (AES) 1215-3S, the sodium
a key attribute of surfactants used in Asian laundry pow- salt of the ethoxysulfate prepared from a three-ethylene
ders. Recent studies determined the relative foaming rate of oxide alcohol ethoxylate. A dynamic spray foam apparatus
AOS 1416 vs. other surfactants in a formulation containing was utilized to measure the flash foamability of the deter-
15% surfactant, 40% sodium tripolyphosphate (STPP), and gent solutions in the absence of soil (5). As shown in Figures
35% sodium sulfate. AOS used in these studies, as well as 3 and 4, both AOS and AES provide higher foam levels than
those discussed in later sections, were prepared from SHOP AE and LAS at 28˚C. The difference in foamability is most
olefins containing >95% normal AO. Other surfactants pronounced with 300 ppm water hardness present. In this
tested included AE 1215-9, a predominantly linear alcohol

FIG. 2. Effect of surfactant structure on sebum detergency; 65:35 poly- FIG. 4. Effect of surfactant on flash foaming; 300 ppm hardness; 28°C;
ester/cotton; 50°C; 1.5 g powder detergent/L. For symbols and abbrevi- 1.5 g powder formulation/L. For abbreviations and symbols see Figures
ation see Figure 1. From Reference 4. 1 and 3.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

 USE OF HIGH-ACTIVE ALPHA OLEFIN SULFONATES IN LAUNDRY POWDERS 363

case, the AOS-containing formulation formed foam at twice TABLE 3

AOS Krafft Temperatures at Different Surfactant Concentrations
the rate of the formulation containing LAS.
Krafft temperature (°C)
Surfactanta 0.1% 1.0% 10.0%
RESULTS AND DISCUSSION AOS 1416 <0 8 10
AOS 1418 10 20 23
Solubility properties of AOS in deionized water. Optimal formu- C16 AOS 12 22 25
lation of a powder laundry detergent requires knowledge of C18 AOS 30 35 38
various fundamental surfactant properties. For anionic sur- AOS 1416 <0 <0 12
factants such as AOS, these include Krafft temperature, i.e., (branched)
a
For abbreviation see Table 1.
the temperature at which a given concentration of surfac-
tant fully dissolves, and the critical micelle concentration
(cmc). If washing temperature is below the Krafft tempera- cases shown in Table 3, increasing surfactant concentration
ture of the surfactant, incomplete dissolution of surfactant increases the temperature required for complete solubility
may occur, causing poor cleaning and deposition of undis- of the surfactant. Also, increasing carbon chain length in-
solved surfactant on the fabric. If surfactant concentration is creases the Krafft temperature of both commercial and sin-
below the cmc at use conditions, poor cleaning also results gle-cut AOS samples at a given concentration. AOS 1418
due to the lack of micelles and, therefore, insufficient surfac- and C16 AOS, having approximately the same average
tant to fully adsorb at the fabric–water and water–soil inter- structure, exhibit comparable solubility properties. Not
faces. This relationship of detergency to phase behavior is surprisingly, AOS prepared from AO enriched in branched
shown schematically in Figure 5 for C12 primary alcohol species (modified Ziegler with approximately 15% branch-
sulfate (6). At the Krafft point temperature, surfactant solu- ing) is somewhat more soluble than the comparable chain-
bility is equivalent to the cmc. length linear AOS at low surfactant concentrations.
Shown in Table 3 are Krafft temperatures in deionized Table 4 shows a comparison of Krafft temperatures of
water for a variety of AOS surfactants. These measure- the sodium salts of AOS and LAS. Both C12 and C13 LAS
ments were performed by freezing 10-g solution samples are more soluble than commercial AOS surfactants at con-
and then monitoring their appearance while warming at centrations below 1%. Also shown in Table 4 are calcium
1°C temperature intervals in a water bath. The point at ion tolerance values for the same samples. The values were
which full solution clarity is obtained at a given surfactant measured at 0.06% active concentration by adding an ap-
concentration is considered the Krafft temperature. In all propriate quantity of 10% CaCl2 solution to 10 g of surfac-
tant solution. After allowing samples to equilibrate in a
40°C oven for at least 3 d, the concentration of surfactant
remaining in the upper clear layer is measured via a two-
phase titration method (7). In the case of C12 LAS, surfac-
tant precipitate did not settle to the bottom but was en-
trained within the liquid as small particles, which had to
be removed by a 1-µm filter. In this study, the concentra-
tion at which one-half the original surfactant had precipi-
tated was taken as the calcium tolerance level.
Results for AOS 1416 are shown in Figure 6. Below 300
ppm calcium chloride, the 0.06% surfactant solution is
clear. Above this level of added calcium, however, a pre-
cipitate forms which separates and falls to the bottom of
the solution. Approximately half of the AOS is precipitated
at 450 ppm added calcium chloride. In contrast, the LAS
sample formed turbid solutions at levels of added calcium

TABLE 4
Krafft Temperatures and Calcium Tolerance of AOS and LASa
Krafft temperature (°C) Ca tolerance
Surfactant 0.10% 1.0% 10.0% (ppm CaCl2)
AOS 1416 <0 8 10 450
AOS 1418 10 20 23 440
C12 LAS <0 <0 4 150
FIG. 5. Solubility curve of C12 primary alcohol sulfate (adapted from C13 LAS <0 <0 13 not measured
Ref. 6). cmc, critical micelle concentration; cmc´; cmc in presence of a
LAS, linear alkylbenzene sulfonate; for other abbreviations see Table 1.
b
other detergent, ingredients, fabrics, and soils. See text for methodology description.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

364 K.H. RANEY ET AL.

FIG. 6. Calcium tolerance plot for AOS 1416 at 40°C. For abbreviation
see Figure 1. FIG. 8. Krafft temperatures of powder detergent (AOS 1416 + cosurfac-
tant). For abbreviations see Figures 1 and 3. Dashed line represents
Krafft temperature of 1.0% AOS 1416 in deionized water.
chloride below 100 ppm. Therefore, despite being more
soluble than AOS 1416 and AOS 1418 in the sodium salt
form, LAS (as the calcium salt) exhibits much lower solu- der formulation containing 20% surfactant, 23% STPP, 23%
bility than Ca AOS. This intolerance to divalent ions typi- soda ash, 20% sodium sulfate, 5% sodium silicate, and 9%
cally results in reduced foaming and cleaning capabilities water. Krafft temperatures were measured at 0.1 and 1.0%
for LAS in hard water. The relatively higher water-hard- total surfactant concentration using various weight ratios
ness tolerance of AOS demonstrated in Table 4 should be of AOS and C12 LAS or AE 1215-9. Corresponding levels
beneficial in regions of Asia having particularly hard of sodium sulfate and builder in solution at the two surfac-
water, such as inland China, and/or for use in phosphate- tant levels are 0.35 and 3.5%, respectively. These concen-
free powder formulations. trations would be encountered transiently in washing so-
The cmc of commercial AOS were determined by mea- lutions as a powder detergent begins to dissolve.
suring surface tension at 25°C as a function of surfactant Shown in Figures 8 and 9 are results for AOS 1416 and
concentration using an automated Lauda tensiometer 1418, respectively. Dashed lines are reference lines show-
(Königshof, Germany). This instrument doses fixed incre- ing the 0.1 and 1.0% Krafft temperatures of the respective
ments of a stock solution into 100 mL of deionized water AOS in deionized water. Without cosurfactant, the Krafft
which is contained in a thermostatically controlled beaker. temperatures of AOS in the presence of dissolved elec-
Equilibrium surface tension is measured automatically trolytes are approximately 6 to 10°C higher than values de-
using the Du Nouy ring method (8). Shown in Figure 7 are termined for deionized water. This can be attributed to
the plots obtained for three commercial samples. Through salting-out effect by electrolytes acting on the anionic sur-
determination of the surfactant concentration above which factant. However, addition of either AE or LAS as a cosur-
surface tension remains nearly constant, cmc for AOS 1418, factant reduces the Krafft temperatures markedly. For AOS
AOS 1416, and AOS 1416 (branched) are estimated to be ap- 1416, approximately 20% AE or LAS relative to AOS is suf-
proximately 0.04, 0.06, and 0.09% by weight, respectively. ficient to reduce the Krafft temperatures at 1% surfactant
Solubility properties of AOS in builder solutions. The equi- concentration below that of AOS in deionized water,
librium surfactant properties described above were mea- whereas about 30% cosurfactant is required for the same
sured in deionized water. However, the builder ingredients effect with AOS 1418. Hence, the reduced solubility of AOS
and other cosurfactants contained in powder detergents in the presence of builders such as STPP and soda ash can
greatly affect a surfactant’s properties in a washing solu-
tion. Hence, Krafft temperature and cmc measurements
were repeated for AOS 1416 and 1418 in a prototype pow-

FIG. 9. Krafft temperatures of powder detergent (AOS 1418 + cosurfac-

FIG. 7. Surface tension vs. AOS concentration at 25°C. ∆, AOS 1418; tant). Dashed lines show the 0.1 (....) and 1.0% (-----) Krafft temperatures
■, AOS 1416; ◆, AOS 1416 (branched). For abbreviation see Figure 1. of AOS 1418 in deionized water. For abbreviations see Figures 1 and 3.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

 USE OF HIGH-ACTIVE ALPHA OLEFIN SULFONATES IN LAUNDRY POWDERS 365

FIG. 10. Effect of detergent components on AOS surface tension at

25°C. ◆ AOS 1418 in deionized water; ● AOS 1418 with builders and
AE; ■ AOS 1416 in deionized water; ▲ AOS 1416 with builders and
AE. For abbreviations see Figures 1 and 3. FIG. 11. Viscosity vs. shear rate for 70% AOS 1416. ◆, 40°C; ■ , 50°C;
▲, 70°C; X, 90°C. For abbreviations see Figure 1.
be counteracted by incorporating small amounts of more
soluble surfactants such as AE 1215-9 or C12 LAS. at high temperature, exhibiting non-Newtonian rheology.
Surface tension measurements of AOS in the presence of Figure 11 shows plots of viscosity vs. shear rate as a func-
the same powder ingredients were also performed. Based tion of temperature for linear AOS 1416 as measured with
on solubility studies, the following formulation was chosen a Rheometrics® Pressure Rheometer (Piscataway, NJ) main-
for use in these experiments: 14% AOS + 6% AE 1215-9, 23% tained at 50 psi nitrogen to minimize water loss. Transition
STPP, 23% soda ash, 20% sodium sulfate, 5% sodium sili- to a solid crystalline phase occurs as the paste cools below
cate, and 9% water. This formulation provides complete sol- 40°C. Figure 12 shows that the presence of approximately
ubility of AOS 1418 below room temperature at 1% surfac- 15% branching in the hydrophobe [AOS 1416(B)] results in
tant concentration and below. The powder components lower viscosities at 40°C as compared to values for linear
were added as a concentrated solution to deionized water material. However, through substitution of 9% water with
to generate plots of surface tension vs. total surfactant con- hexylene glycol or propylene glycol, viscosity of linear
centration. Hence, the relative proportion of all ingredients AOS paste can be reduced substantially to below that of
was kept constant. Results of the tests are shown in Figure branched AOS. In addition to reducing viscosity, incorpo-
10 along with original surface tension curves for AOS in ration of 9% propylene glycol reduced yield stress of the
deionized water. The presence of dissolved electrolytes and paste at 50°C by a factor of three.
nonionic AE 1215-9 increases the surface activity of AOS Rheology of high-active blends of AES and primary al-
and reduces cmc as indicated by low surface tensions ob- cohol sulfates (PAS) with AE has been reported (10). For
tained at very low surfactant levels. For both AOS systems, many systems, low-viscosity liquids containing greater
cmc levels below 0.01% by weight surfactant are apparent, than 90% surfactant were found at room temperature even
indicating that acceptable cleaning performance is obtain- for AES/AE ratios greater than one. Similar studies with
able in that concentration regime. AOS have now been done to determine its usefulness in
Physical forms of AOS. The previous sections have de- this type of binary system.
scribed the relationship of AOS chemical structure to Figure 13 shows viscosity vs. shear rate as a function of
cleaning performance and solubility of detergent powders. temperature for a 2:1 by weight blend of a predominantly
In summary, excellent detergency and foaming can be ob-
tained using AOS as a primary surfactant as long as AOS
solubility properties in the formulation are taken into ac-
count. Similarly, the effects of AOS physical structure on
powder detergent production and physical properties
must be considered.
AOS has commonly been produced and marketed as
approximately 30- to 40%-active solutions in water. Owing
to its low Krafft temperature boundary, AOS 1416 is a clear
liquid up to 40% concentration with a viscosity less than
200 cP. AOS 1418 and 1618 are typically produced as 30- to
35%-active two-phase slurries. These materials are not
clear solutions, because Krafft temperatures are above
room temperature in this concentration range.
FIG. 12. Viscosity vs. shear rate at 40°C for 70% AOS 1416. ◆, AOS
Similar to AES and primary alcohol sulfates, AOS can 1416; ■, AOS 1416(B), with presence of approximately 15% branching
be neutralized directly to a 70%-active lamellar liquid crys- in the hydrophobe; ▲ , AOS1416 + 9% hexylene glycol; X, AOS 1416
talline phase (9). A 70% AOS paste is thick, but pumpable + 9% propyleneglycol. For abbreviation see Figure 1.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

366 K.H. RANEY ET AL.

linear AE based on a C12 to C13 hydrophobe with an aver-

age of 6.5 EO groups (AE 1213-6.5) with AOS 1416. This
blend was prepared by thorough mixing of dry AOS pow-
der with appropriate quantities of AE and water at 40°C.
Pseudoplastic behavior is noted with relatively low viscosi-
ties occurring at high shear rates. Similar results were noted
for a mixture prepared with AOS 1418. Higher proportions
of AOS, however, resulted in formation of intractable gels
even at elevated temperatures. Figure 14 compares AOS sys-
tem rheology with other high-active 2:1 AE/anionic blends
prepared by direct neutralization of the acid form of surfac-
tant in a mixture of 50% sodium hydroxide and AE. Appar-
ently owing to its high crystallinity, AOS produces the high-
FIG. 14. Viscosity of 2:1 AE 1213-6.5/anionic high-active systems
est viscosity among the systems which have been examined. (>95% surfactant). ◆, AOS 1416; ■ , C12–15 primary alcohol sulfate;
In contrast, AES and LAS form flowable liquid systems with ▲ C12 LAS; X, AES 1215-35. For abbreviations see Figures 1 and 3.
AE well below room temperature.
Spray-dried AOS granules have been available for many
years (11). However, new more energy-efficient methods of
producing dry powder forms of anionic surfactants are cur-
rently available (12). Representative particle size distribu-
tions of AOS 1416 and 1418 powder (ASCO® 93 and 90 ob-
tained from Aekyung & Shell Co., Daejon, Korea) contain-
ing 98 and 97% active surfactant, respectively, are shown in
Figure 15. These distributions were obtained by sieving the
surfactant powders using standard test sieves.
A wide range of particle sizes is noted with approxi-
mately 60% by weight of the powder particles between 45
and 250 µm in size. The powders are free-flowing and non-
hygroscopic. Some dustiness was noted due to the pres- FIG. 15. Particle-size distribution of AOS powders; open bar, AOS1416;
ence of very small particles less than 38 µm in diameter. lined bar, AOS 1418. For abbreviation see Figure 1.
Figure 16 shows photomicrographs of three powder frac-
tions of AOS 1418. These images were taken using environ- other detergent ingredients, fabrics, and soils (schemati-
mental scanning electron microscopy (ESEM) (13). With cally represented in Fig. 5), the relationship between mini-
this technique, samples were imaged in a nonvacuum en- mal powder detergent dosage and properties of the pow-
vironment. The micrographs show that AOS powder ex- der detergent can be written as follows:
ists as distinct irregularly shaped particles with no agglom-
cmc ′ (g/L)
eration of smaller particles. Minimum powder dosage (cm 3 / L wash water) = [1]
(wt. frac. surfactant) [powder density (g/cm3 )]
Incorporation of AOS into powder detergents. Both solution
properties and powder physical properties affect a powder
detergent’s dosage level. By assuming that the minimum
required concentration of surfactant in wash water for ef-
fective cleaning is cmc′, i.e., the cmc in the presence of

■ ), and 40°C (▲
FIG. 13. Viscosity vs. shear rate; at 80°C (◆), 65°C (■ ▲ ). FIG. 16. Environmental scanning electron microscopy micrographs of
Test solution contained 64% AE 1213-6.5, 32% AOS 1416, and 4% AOS 1418 powder fractions. For abbreviations see Figure 1. A: 38–45
water. For abbreviations see Figures 1 and 3. µm; B: 63–90 µm; C: 250–425 µm. Scale bar = 50 microns.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

 USE OF HIGH-ACTIVE ALPHA OLEFIN SULFONATES IN LAUNDRY POWDERS 367

For a compact detergent, which by definition has a low vol- Powder AOS could potentially be used in either dry
ume dosage requirement, it is desirable to have a low cmc′, blending or agglomeration processes. However, when
a high weight fraction of surfactant in the powder, and a used in a dry-blended product, AOS powder would need
high powder density. As already shown in Figure 10, to have a narrow distribution of particle sizes to prevent
builders, sodium sulfate, and AE are effective in reducing segregation of ingredients in the box. Also, the potential
cmc′ for AOS-based powders to low levels, thereby reduc- for dustiness due to small surfactant particles, e.g., those
ing powder dosage levels as well. For the formulation dis- less than 30 µm, would need to be managed.
cussed in the section headed Solubility properties of AOS in For any detergent product prepared from AOS powder,
builder solutions, a minimal dosage of 0.71 cm3/L is calcu- it is important to know how quickly the AOS particles will
lated for cmc′ = 0.1 g/L and powder density = 0.7 g/cm3. dissolve in wash water so that maximal cleaning effective-
Figure 17 schematically represents the powder deter- ness is obtained and surfactant residue is not left on the
gent densities achievable using various forms of powder fabric. In this regard, a dipping probe turbidimeter system
processing (14). As mentioned previously, aqueous solu- has been used to measure rates of dissolution of both AOS
tions of AOS are useful for producing low-density spray- 1416 and 1418 powders as a function of particle size. With
dried powders. However, agglomeration and dry blending this apparatus, a fiber optic probe is used to measure tur-
of detergent powders containing high proportions of AOS bidity (as % light absorbance) within a well-stirred solu-
require high-active forms of the surfactant. In this regard, tion as a function of time (19). Figure 18 shows the turbid-
70% AOS paste could be utilized in high-shear agglomera- ity trace after addition of 0.3 g of the 150–250 µm fraction
tion processes. Recent patents have described processes by of AOS 1418 to 100 mL deionized water at 20°C. Complete
which high-active pastes of anionic surfactants are mixed solubility of AOS powder after about one-half minute is
with fine powder builders such as zeolite to produce con- noted. Figure 19 shows the times required for dissolution
centrated detergent powders (15). This type of process re- of AOS 1416 at 10°C and AOS 1418 at 20°C. These temper-
quires the use of special high-shear mixing equipment to atures are just above the Krafft temperatures for the two
break the paste/builder agglomerates into acceptably surfactants. Despite being studied at the lower tempera-
small detergent particles (15,16). While liquid agglomera- ture, AOS 1416 was found to be more rapidly solubilized
tion processes require low-viscosity surfactants to allow than AOS 1418. As expected, larger particle sizes require
spraying and uniform mixing with builder particles, pastes longer times to dissolve. However, even at this relatively
having a viscosity greater than about 10,000 cP at a shear high surfactant level, the largest particles dissolve within 3
rate of 25 s−1 have been reported to be desirable for the min, well before the end of a typical washing cycle. For
paste agglomeration process (16). As shown in Figure 11, particle sizes smaller than 90 µm, aggregation or clumping
70% AOS 1416 meets this criterion at temperatures be- of particles occurred upon addition to the water which pre-
tween 40 and 60°C. vented a further reduction in solution time. In both sys-
For powders containing AE and a relatively small pro- tems, 0.3 g of the total unsieved sample required about the
portion of AOS, high-active blends of AE and AOS could same time to dissolve as that of its largest size fraction.
be sprayed onto builder supports at high temperatures to To investigate the effects of other detergent ingredients
agglomerate the builder materials and produce powder on the kinetics of AOS 1418 powder dissolution, the proto-
products having high bulk density. The pseudoplastic na- type powder formulation described in the section Solubil-
ture of these blends would help minimize “bleeding” of ity properties of AOS in builder solutions was used. In this
AE into the detergent box. Processes for incorporating case, STPP, soda ash, sodium sulfate, sodium silicate, and
high-active AE/anionic systems in agglomerated powders AE 1215-9 were predissolved in the water at appropriate
have recently been disclosed (17,18). weight ratios. Then 0.3 g of sieved fractions of AOS 1418

FIG. 18. Dissolution of AOS 1418 powder (150–250 µm) in deionized

water at 20°C. Surfactact concentration 0.3 wt%. For abbreviations see
FIG. 17. Powder detergent production processes (adapted from Ref. 14). Figure 1.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

368 K.H. RANEY ET AL.

FIG. 19. Dissolution times of AOS powder in deionized water. Solid

FIG. 20. Dissolution times of AOS 1418 powder at 20°C. Horizontally
bars, AOS 1416 at 10°C; slashed bars, AOS 1418 at 20°C. For abbrevi-
lined bars, deionized water; solid bars, with builders and AE. For abbre-
ation see Figure 1.
viations see Figures 1 and 3.

powder was added. At a 0.3% AOS level, complete solu-

bility at 20°C was predicted. A comparison of the results • Spray sodium silicate solution.
for selected particle sizes to those obtained in deionized • Spray AE 1215-9 liquid.
water (Fig. 20) indicates that the presence of dissolved • Add AOS 1418 powder.
builder and AE significantly increases the solution times • Add 5% zeolite powder (in place of equivalent amount
of the surfactant particles. These results indicate that it is of STPP).
beneficial to prepare a detergent powder so that some AOS • Condition for 1 h at 70°C.
dissolution occurs prior to dissolution of other ingredients.
Preparation of compact detergents containing AOS powder. Zeolite addition was found necessary to modify the ag-
To determine suitable processes for preparation of agglom- glomerate surface and improve flowability. No dustiness
erated detergent powders containing AOS 1418 powder, was observed in the sample indicating that all AOS and ze-
a specially modified Visco-Corder® viscosimeter from olite are adsorbed onto the agglomerate surface. After re-
Brabender Instruments (S. Hackensack, NJ) was used to moval of particles greater than 1000 µm size by sieving, an
prepare several lab-scale samples. The instrument allows unpacked bulk density of 0.69 g/cm3 was measured for the
effective small-scale mixing of powders and liquids (20,21). sample. A comparison of the physical properties of labora-
Specifically, the procedure involves spraying liquid silicate tory-prepared detergent powder containing AOS to those
and/or liquid surfactant onto approximately 100 g of for two zeolite-built private-label Japanese detergents is
builder powder mixing in a rotating cup. A special double- shown in Table 5. Funnel flow rate studies were made to
flag paddle is used for mixing the powder ingredients. compare the flowability of various powder formulations.
Spraying of the liquid ingredients is achieved through use For these measurements, the time required for 50 g of de-
of a Sono-Tek Microspray™ (Poughkeepsie, NY) ultrasonic tergent to pass through a standard funnel attached to a vi-
atomizing nozzle. The fine mist produced by the nozzle al- brating stand was measured in triplicate. These tests
lows efficient coating and agglomeration of solid particles yielded an average flow rate of 6.5 g/s for the lab-pro-
by liquids including relatively viscous sodium silicate so- duced sample as compared to 6.8 and 7.5 g/s for the two
lutions. In this study, the rotation of the mixing bowl was commercial products.
maintained at 100 rpm, and the liquid ingredients were As indicated in Figure 9, this experimental powder for-
added at 40°C at a fixed rate of 2.2 mL/min by a gear-dri- mulation has a Krafft temperature of approximately 18°C
ven syringe pump. at 1% surfactant concentration and a Krafft temperature
The formulation used as the basis for these studies was below 0°C at 0.1% surfactant concentration. Therefore, at a
presented in the section headed Solubility properties of AOS in typical use concentration of 1.5 g powder detergent/L
builder solutions. Low-density STPP and Grade 100 soda ash (0.03% surfactant concentration), the experimental powder
(FMC Corporation, Philadelphia, PA) and Valfor® 100 zeolite (except zeolite) was predicted to be completely soluble in
(The PQ Corporation, Valley Forge, PA) were used as builder cold deionized water. Powder dissolution studies at this
components. Sodium sulfate powder and sodium silicate so- concentration using the dipping probe turbidimeter sys-
lution (41 Baumé) were obtained from Baker Scientific tem confirmed that good dissolution (>98%) of surfactant
(Phillipsburg, NJ). For these raw materials, the optimal se- and builder occurred within 1 min at 20°C. Kinetic solubil-
quence of ingredient addition was found to be the following: ity results along with those for the Japanese commercial
products are given in Table 5. Although eventually solu-
• Mix STPP, soda ash, and sodium sulfate. ble, the experimental powder required significantly longer

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)

 USE OF HIGH-ACTIVE ALPHA OLEFIN SULFONATES IN LAUNDRY POWDERS 369

TABLE 5 ter Alcohol Ethoxysulfate/Alcohol Ethoxylate Blends, J. Am.

Comparison of Properties of Laboratory-Prepared Agglomerated Oil Chem. Soc. 66:1647–1650 (1989).
Powder Detergent to LAS-Based Japanese Commercial Productsa 11. Cullotta, C.P., and A. Shultz, A Spray-Dried Alpha-Olefin
Flow 98% Dissolution time (min) Sulfonate from Concept to Marketplace, J. Am. Oil Chem. Soc.
Density rate (1.5 g/L) 59:211–216 (1982).
Detergent (g/cm3) (g/s) 1°C 10°C 20°C 12. Anonymous, Indian Firm to Use New Drying Technology,
INFORM 5:1002 (1994).
Lab. 1 0.69 6.5 30 7 1 13. Raney, K.H., and J.H. Rask, Use of Environmental Scanning
Com. 1 0.68 6.8 8 10 14 Electron Microscopy in Detergent Studies, in Proceedings of 3rd
Com. 2 0.68 7.5 5 4 2 CESIO International Surfactants Congress, London, 1992, pp.
a
Lab. 1: Sample 1, prepared in the laboratory; Com. 1 and Com. 2: two ze- 101–121.
rolite-built private-label Japanese detergents. For abbreviation see Table 4. 14. Dolan, M.J., A Review of Detergent Agglomeration Technol-
ogy, Soap Cosmet. Chem. Spec. 63(3):33–37 (1987).
15. De Ryck, B., P. Van Dijk, and J.L. Vega, Mfg. High Active De-
times to dissolve in cold water. Interestingly, one of the tergent Granules with Excellent White Appearance and High
commercial formulations dispersed somewhat more Bulk Density, European Patent Application 578,872-A1 to
quickly as water temperature was reduced. These findings Procter & Gamble Co. (1994).
illustrate that nonequilibrium solubility studies as well as 16. Aouad, Y.G., J.L. Vega, and P. Van Dijk, High Active Deter-
equilibrium Krafft temperature measurements are needed gent Pastes with Good Rheological Properties, European
Patent Application 560,001-A1 to Procter & Gamble Co.
to fully understand the performance properties of a formu- (1993).
lated powder detergent. 17. Akkermans, J.H.M., H. Euser, C. Joyeux, and P.I.J. Swinkels,
Detergent Compositions and Process for Preparing Them, Eu-
ropean Patent Application 554,365-A1 to Unilever NV (1993).
ACKNOWLEDGMENT 18. Dumas, P., T.T. Lio, C.J.R. Ormancey, F.L.G. Hsu, and R.J.
The authors wish to acknowledge Greg York for performing the Ahart, Process for Preparing a High Bulk Density Detergent
environmental scanning electron microscopy studies. Composition Having Improved Dispensing Properties, Euro-
pean Patent Application 436,240-A1 to Unilever NV (1991).
19. Raney, K.H., and H.L. Benson, The Effect of Polar Soil Com-
REFERENCES ponents on the Phase Inversion Temperature and Optimum
Detergency Conditions, J. Am. Oil Chem. Soc. 67:722–729
1. Van Os, N.M., R. Van Ginkel, A. Van Zon, F.W. Heywood, (1990).
E.L. Berryman, and J.K. Borchardt, Olefinsulfonates, in An- 20. Absorptivity Testing, FMC Corporation Detergent Applica-
ionic Surfactants: Organic Chemistry, edited by H.W. Stache, tions Bulletin No. 10, Philadelphia.
Marcel Dekker, New York, 1994, pp. 363–459. 21. Merrill, C.L., Development of a Nonionic Surfactant-Based
2. Mori, A., and O. Okumura, Development of AOS as a Raw High Density Laundry Powder, presented at the Southwest
Material for Detergents and Toiletries, in Proceedings of 1st Section American Oil Chemists’ Society Meeting, Buena Park,
CESIO International Surfactants Congress, Munich, 1984, pp. CA, 1987. [Reprinted as Shell Chemical Company (USA)
93–104. Technical Bulletin SC:968-91.]
3. Turner, A.H., Purity Aspects of Higher Alpha Olefins, pre-
sented at American Oil Chemists’ Society Meeting, Toronto, [Received December 9, 1997; accepted April 29, 1998]
1982. [Reprinted as Shell Chemical Company (USA) Techni-
cal Bulletin SC:776-83.] Kirk H. Raney is a senior research engineer who joined Shell
4. Brown, E.A., L. Kravetz, D.H. Scharer, and H. Stupel, The Per-
Chemical Company’s Westhollow Technology Center in Hous-
formance of Alpha Olefin Sulfonates in Light-Duty and Heavy-
Duty Household Detergents, presented at American Oil ton, Texas, in 1985. He received his B.S. in chemical engineering
Chemists’ Society Meeting, New Orleans, 1976. [Reprinted as from the University of Tulsa and his M.S. and Ph.D. from Rice
Shell Chemical Company (USA) Technical Bulletin SC:149- University. His current research interests include detergency fun-
77.] damentals and surfactant applications in household detergents.
5. Schmidt, W.W., D.R. Durante, R. Gingell, and J.W. Harbell,
Paul G. Shpakoff is a senior research technician at Shell
Alcohol Ethoxycarboxylates—Mild, High-Foaming Surfac-
tants for Personal Care Products, J. Am. Oil Chem. Soc. Chemical Company’s Westhollow Technology Center in Hous-
74:25–31 (1997). ton, Texas. Since joining Shell in 1985, he has worked in deter-
6. Schambil, F., and M.J. Schwuger, Interfacial and Colloidal gency fundamentals and surfactant kinetics and research method
Properties, in Surfactants in Consumer Products, edited by J. development. Additional R&D studies have been in the use of
Falbe, Springer-Verlag, Heidelberg, 1987, p. 134.
surfactants in paper processing and enhanced oil recovery.
7. Reid, V.W., G.F. Longman, and E. Heinerth, Determination of
Anionic-Active Detergents by Two-Phase Titration, Tenside Deborah Passwater joined Shell Chemical Company at West-
4:292–304 (1967). hollow Technology Center in 1986. As a senior research techni-
8. Davies, J.T., and E.K. Rideal, Interfacial Phenomena, Academic cian, her areas of work included detergent and surfactant re-
Press, New York, 1963, p. 43. search including fundamental property evaluation, application
9. Van Zon, A., R. Kok, and A.K. Van Helden, Effect of Hy-
and performance testing, and method development. She also
drophobe Structure on the Properties of Primary Alcohol Sul-
fates, in Proceedings of 3rd CESIO International Surfactants Con- worked in engine coolant research and technical support. Her
gress, London, 1992, pp. 225–232. current position is ethylene oxide/ethylene glycol product spe-
10. Kravetz, L., and H.L. Benson, Solvent-Free High Active Mat- cialist.

Journal of Surfactants and Detergents, Vol. 1, No. 3 (July 1998)