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Technical Information

Dispex A40

EDC 008811 e, March 2011supersedes any documents issued by former CIBA regarding this product page 1 of 3

dispersing agentgeneral

Dispex A40 is a derivative of a family of highly effective, low-viscositydispersing agents for water-based coating systems, especially suit-able for the dispersion of inorganic pigments.

chemical nature solution of an ammonium salt of an acrylic polymer in water

Properties

physical fo rm straw-colored liquid

shelf life Although Dispex A40 is freeze-stable it should be stored at tempera-tures above 5 C (41 F) to allow easy handling.

solvent waterdensity at 20 C (68 F) ~ 1.30 g/ cm3

solid content ~ 45 %

active content ~ 40 %visc osity at 20 C (68 F) ~ 400 mPa . s

typical properties(no supply specification)

pH ~ 7.5

Application

Dispex A40 preparations are ideal dispersing agents for a wide rangeof water-based coatings. They can be used as supplied.

The neutralizing alkali used in conjunction with the acrylic polymer cansignificantly impact the p roperties of the final coating. Dispex A40releases ammonia during the drying process and therefore has littleimpact on the resistances to water and alkali of the dry film.

The use of Dispex A40 should be limited to pH 5 10.5 and tem-peratures lower than 70 C (158 F) due to potential loss of volatileammonia.

Dispex A40 is based on an organic polymer and provides improvedstorage stability of both pigment dispersion and formulated paintwhen compared with inorganic dispersing agents, e.g., polyphosphateproducts. There is little or no adverse reaction to high temperatures orpH changes as indicated in the graphs below (examples showing theaccelerated effects).

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EDC 008811 e, March 2011 page 2 of 3 Dispex A40

0

500

1000

1500

2000

2500

3000

0 10 20 30 40 50

hours after coating application

20rpm

Brookfieldviscosity

[mPa.s

]

Dispex A40 polyphosphate

stability of pigment dispersion tointeractions between basic pigmentand dispersing agent

acrylic latex containing china clay and CaCO3, stored at 20 C (68 F)

0

500

1000

1500

2000

2500

0 10 20 30 40 50

hours after coating application

20rpm

Brookfieldviscosity

[mPa.s

]

Dispex A40 polyphosphate

stability of pigment dispersion to heat)

acrylic latex containing china clay, stored at 50 C (122 F)

As opposed to adding the dispersing agent to a pigment slurry, thepigment should be added to heavily stirred water to which the dis-persing agent had been added. In general, the pH of the final prepara-

tion should be in the region of 8.5 to obtain optimum dispersingefficiency.

incorporation

The optimum amount of dispersing agent required to form a stabledispersion strongly depends on the p igments chemical nature, theparticle surface and shape. The polymer base of the latex also plays avery important part in the stability equation. In general, significantoverdosing may deteriorate the coatings properties (e.g., water resis-tance) and generate an economic disadvantage. Likewise, insufficientdispersing agent will lead to instability on storage.

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EDC 008811 e, March 2011 page 3 of 3 Dispex A40

SafetyWhen handling this product, please comply with the advice and information given in the safety data sheet and observe protective and workplace hygiene measuresadequate for handling chemicals.

NoteThe data contained in this publication are based on our current knowledge and experience. In view of the many factors that may affect processing and applicationof our product, these data do not relieve processors from carrying out their own investigations and tests; neither do these data imply any guarantee of certain prop-erties, nor the suitability of the product for a specific purpose. Any descriptions, drawings, photographs, data, proportions, weights, etc. given herein may changewithout prior information and do not constitute the agreed contractual quality of the product. The agreed contractual quality of the product results exclusivelyfrom the statements made in the product specification. It is the responsibility of the recipient of our product to ensure that any proprietary rights and existing lawsand legislation are observed.

= registered trademark, = trademark of BASF Group, unless otherwise noted

BASF SEPerformance Additives67056 Ludwigshafen, Germanywww.basf.com/resins

dispex_l_a40_ti_edc008811_lb_e_20110322_final.doc | EDC 008811-1103 E service-edc@basf.com

As with other dispersing agents and because of the batch-to-batchvariations of a specific p igment or latex t ype, the formulator shoulduse 1.5 2.0 times the determined optimum level of dispersing agent.

rheology curve of a pigment slurry

(65 % pigment solids)

0

500

1000

1500

2000

2500

3000

3500

0.0 0.1 0.2 0.3 0.4 0.5

% Dispex A40 (based on pigment weight)

20rpm

Brookfieldviscosity

[mPa.s

]

Dispex A40

recommended concentrations 0.52.0 % on total pigment weight

optimumconcentration