Rohm and Haas


ACUSOL™ 820 Rheology Modifier and Stabilizer

Description

ACUSOL 820 is a Hydrophobically modified Alkali Soluble acrylic polymer Emulsion (HASE) with unusually high aqueous thickening and stabilising efficiency. When neutralised to a pH above 7 by adding alkalis, ACUSOL 820 thickens instantly. The instantaneous effect on viscosity and easy incorporation of ACUSOL 820 into alkaline cleaner formulations offer savings in valuable production time that cannot be matched by carbomer or cellulosic thickeners, requiring predissolution and elimination of lumps.

Working by association, ACUSOL 820 can also thicken solutions containing high levels of surfactants at low pH. This unique performance is achieved by acidifying a neutralised surfactant-containing formulation with a dilute organic or mineral acid.

Features

Benefits

Anionic

Can be thickened instantly with any alkali. Compatible with both non-ionic and anionic surfactants, builders and fillers.

Liquid

Supplied as a low viscosity liquid emulsion, it is very easy to handle. No predissolution, elimination of lumps or warming required.

Associative nature

Association may occur with other formulation components giving enhanced viscosity and stability.

Rheology

Gives pseudoplastic (shear thinning) rheology, similar to cellulosics but maintains higher viscosity for higher shear rates.

Emulsion technology

Water based polymerization. No residual solvents. No residual organic initiators.

Instant neutralization

Permits continuous manufacturing process through in-line static mixers.

Gel appearance

Gives clear gels or solutions.

Microbial resistance

Being a synthetic polymer, it is inherently resistant to microbes and enzymes that can degrade cellulosic thickeners, leading to loss of viscosity.

Salt tolerance

Compatible with high levels of salts and electrolytes commonly used in household and institutional formulations.

Recommended Applications

ACUSOL 820 thickener is highly cost-effective for the following applications:

Emulsion cleaners
Glass cleaners
Hand dishwash liquid detergents
Hard surface and floor cleaners
Liquid abrasive cleaners
Liquid laundry detergents
Oven cleaners
Paint strippers
Waterless cleaners
White-wall tire cleaners

Formulation Guidelines

ACUSOL 820 thickener is compatible with surfactants, solvents, oils, salts and other ingredients commonly found in detergent and cleaner products. Formulators of detergents and cleaners will have no difficulty in discovering the best way to incorporate ACUSOL 820 into their own specific products.

General Mixing Procedure

Operating flexibility is provided by the physical characteristics of the product (low viscosity liquid before neutralisation), and its high thickening efficiency allows varying operating procedures. The following mixing procedure meets most formulating needs:

  1. Introduce ACUSOL 820 into the formulation water. This should provide at least a threefold dilution of the polymer.
  2. Add the nonionic surfactants (if any).
  3. Add the anionic surfactants (if any) - low pH first. *
  4. Add builders, fillers, particulates.
  5. Add dyes, then perfume.
  6. Neutralize with the chosen alkali.

* In the case of strongly acidic components, such as sulphonic acids, it is preferable to disperse this component in the system and partially neutralize (e.g.- to pH about 4-5) prior to addition of the polymer.

Rapid Mixing Technique

ACUSOL 820 undergoes instantaneous thickening when a base is added. An in-line mixing technique using a static mixer along with a simple pump affords a convenient, rapid means of producing thickened solutions and gels. The solutions prepared by this technique are free from air bubbles.

For example, pumping solutions of ACUSOL 820 (4% polymer solids) and sodium hydroxide (0.74%) at equal rates through a static mixer gave 115 kg/hr of a clear foam-free gel (Brookfield viscosity 2 x 106 mPa s at 0.5 rpm) containing 2% ACUSOL 820 solids. A small laboratory pump run at maximum speed gave the same output rate as in pumping deionized water. Although this example used only two feed streams, more feeds could be combined, depending on the type of formulation and the compatibility of the ingredients (see below).

Performance Properties

Thickening Efficiency

ACUSOL 820 thickener is a low viscosity dispersion that becomes a highly viscous clear solution when neutralized with alkali. Figure 2 shows the pH profile of sodium hydroxide neutralized ACUSOL 820 where a stable viscosity plateau is observed, and viscosity drops at pH values below 7.5 and above 12.5. This pH/viscosity profile may change in the presence of surfactants (see Associative Nature).

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Figure 3 shows the thickening performance at various Brookfield rotational speeds as a function of the polymer concentration.

Figure 4 compares its efficiency with that of a cellulosic and a carbomer thickener, demonstrating its pH tolerance. Besides sodium hydroxide, other bases, such as ammonia, soda ash (Na2CO3) and TEA, can be used as neutralizing agents.

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Effect of Temperature on Viscosity

As with most formulations, products thickened with ACUSOL 820 will generally show a drop in viscosity with increasing temperature (Figure 5). This effect, which is common to most thickeners, is reversible with a decrease in temperature.

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Effect of Shear Rate on Viscosity

As shown in the graph below (Figure 6) the rheology of ACUSOL 820 is extremely pseudoplastic (shear thinning).

Under good mixing conditions, ACUSOL 820 thickens instantly upon adding a base and thereby allows rapid preparation of solutions and products. Viscosity profiles are very similar, irrespective of the base employed. No pre-wetting, high shear mixing, and long soak times, often required for other thickeners, are needed to dissolve the un-neutralized polymer. The aqueous neutralized solutions are clear, and they show short rheology as well as being shear thinning. Consequently, the solutions are very viscous at low shear rates, as shown in Figure 6.

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Associative Nature

ACUSOL 820 polymer has long hydrophobic chains that can associate with other hydrophobes present in the formulation (e.g. surfactants, particles etc.). This feature can enhance thickening in the case of low pH formulations, where polymer swelling is limited. The synergistic effect depends on the surfactant concentration: maximum viscosity can be obtained at an optimum concentration. With sodium lauryl sulphate (SLS), for example, the maximum occurs when the ratio of the surfactant to ACUSOL 820 solids level reaches 40% (i.e. a ratio of 0.4:l ). Figure 7 illustrates the synergistic effect of ACUSOL 820 in the presence of SLS. In this graph, the polymer concentration required to obtain a given viscosity over a range of surfactant concentrations is shown. For ACUSOL 820, the polymer performance remains good through a wide range of surfactant concentrations, whereas steadily increasing levels of a non-associative polymer are required to maintain a given viscosity.

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Mixture with Bentonite Clays

The addition of low cost bentonite clays appreciably increases the thickening efficiency of ACUSOL 820. Free-standing gels can be obtained by combining appropriate levels of neutralized thickener with bentonite clays (Figure 8).

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Compatibility with Inorganics

ACUSOL 820 can be used even in the presence of relatively high levels of inorganic salts, such as sodium chloride. Efficacy is reduced, but the polymer remains capable of thickening concentrations of salt even at a level of several percent. This is illustrated in Figure 9.

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Typical Physical Properties
These properties are typical but do not constitute specifications.

Appearance

Off white milky emulsion

Polymer type

Associative anionic acrylic

Solids

30%

pH (as supplied)

2.7

Density

1.06

Viscosity (as supplied)

15 Brookfield mPa.s/cps

Acid value

11.7 mls. N/10 NaOH per g product

Preparation of Emulsions and Dispersions

Neutralized ACUSOL 820 thickener can also be used to make oil-in-water emulsions of organic liquids, such as mineral oil, methylene chloride or kerosene, and to suspend fillers and pigments, such as calcium carbonate, silicate clays and titanium dioxide in water. ACUSOL 820 may be useful in thickening aqueous waste materials and absorbing spills of hazardous wastes as well as in removing water from water-immiscible oils and hydrocarbon solvents.

Storage/Handling

Keep from freezing. This emulsion product as supplied will irreversibly coagulate upon freezing.

Avoid high shear pumps when handling this product.

Toxicity

Test/Species

Results

ACUSOL 820 (as supplied)

Acute oral LD50 (rat)

> 5 gr/kg - practically non-toxic

Acute dermal LD50 (rabbit)

> 5 gr/kg - practically non-toxic

Eye irritation (rabbit)

moderately irritating

Skin irritation (rabbit)

slightly irritating (primarily irritation Index 0.9)

ACUSOL 820 neutralized 90% with NaOH, tested at 1% a.i.

Acute oral LD50 (rat)

> 5 gr/kg - practically non-toxic

Acute dermal LD50 (rabbit)

> 5 gr/kg - practically non-toxic

Skin sensitization (guinea pig)

no indication of sensitization in occluded patch test

Material Safety Data Sheets

MSDS are available for all Dow products. These sheets contain pertinent information that you may need to protect your employees and customers against any known health or safety hazards associated with our products.

We recommend that you obtain copies of the MSDS from your Dow technical representative, or from the sales office nearest to you, before using our products in your facilities. We also suggest that you contact your suppliers of other materials recommended for use with our products for appropriate health and safety precautions before using them.

To obtain samples, technical assistance, a Material Safety Data Sheet (MSDS) or to have a technical representative call for an appointment, contact the nearest Dow branch office.