29 January 2009 - Issue 7

This e-newsletter from the Laponite Team is sent to Rockwood Additives and SCP commercial and technical staff worldwide and is also circulated within Rockwood’s global distribution partner network. From Issue 7 onwards it will be available to a wider audience on the Laponite web site: www.laponite.com. Please forward this e-newsletter to any customers who may be interested in reading it.

We hope you find the information useful and thank you for taking the time to read it!

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In Issue 7…

·    We… review the properties …and… advantages …of Laponite sol forming grades and introduce a… new sol forming technology…

Did you know???...we have recently added new technical content to the Laponite web site??? Check it out on the link oppositeèèèèè

·       new application bulletins

·       a “What’s New” section

·       a link to Laponite e-newsletters

Laponite sol forming grades

The ability to produce concentrated, low viscosity dispersions of Laponite that “activate” when added to a range of different types of formulation has many advantages to the formulator. These low viscosity dispersions of Laponite in water are called “sols”.

As a general recommendation, we advise customers who are formulating with Laponite to avoid the preparation of a viscous pre-gel in water. If a strongly gelled Laponite pre-mix is added into a liquid formulation, then the gel and liquid components can behave as if they are “out-of-phase” with each other and it may be difficult to get the Laponite gel component dispersed homogeneously into the rest of the formulation. If this happens it will often lead to formation of gel seeds or grits in the system.

Laponite sol forming grades can be used to solve this problem.

Some types of dispersing agents can prevent, or delay, viscosity build with Laponite by interfering with the mechanism of gel formation. They do this by peptising – keeping separate- the individual 25 nm diameter platelets of Laponite. When the platelets cannot interact and bond with each other, Laponite mixtures in water can easily be produced as low viscosity sols. When the sol dispersion is added into many different types of formulated products, the peptising effect of the dispersant is overcome and the combination will activate to give a gel structure.

Rockwood offers a range of Laponite products that we describe as “sol forming grades”. These products are supplied ready modified with optimised levels of tetrasodium pyrophosphate or other, patented, additives. A brief summary of these grades is shown in the table below:

“Typical sol stability” refers to the length of time that

the dispersion of Laponite remains as a low viscosity liquid

As an alternative to using sol grades, it is also possible to temporarily “de-gel” Laponite RD, or XLG, with polyols. For example, addition of low molecular mass polyethylene glycol (PEG), or polypropylene glycol (PPG) to a Laponite RD dispersion in water will delay the formation of gel structure. Typically, a dispersion of Laponite RD at 4% concentration in water will form a rigid gel that would be difficult to handle within minutes. Following the process described below will allow a low viscosity pre-mix to be made.

The benefit of using this process is that this pre-mix is easier to incorporate into formulations such as automotive paints and wood coatings which often have very low levels of free water available to make the Laponite pre-mix. It allows a low viscosity mixture of Laponite to be stirred into a low viscosity resin system, where the de-gelling effect that the PEG or PPG has upon the Laponite is overcome by other ingredients in the paint and viscosity increase will be seen within seconds.

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Advantages of using Laponite sol forming grades

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New Laponite sol forming technology using polyacrylates

Rockwood has developed a new technology to produce temporary sol dispersions with Laponite. This is based upon use of sodium or ammonium polyacrylates to peptise the Laponite platelets; best results have been obtained with ammonium polyacrylate.

More information on this is available from Rockwood. Click here to request a copy of the application bulletin

L478-08j Phosphorus-Free Laponite Sols, or send your questions by e-mail to help@laponite.com.

A procedure for making a sol dispersion containing 8% Laponite solids with ammonium polyacrylate is shown in the table below. At this concentration, the dispersion will remain fluid for up to 24 hours. When it is added to a suitable formulated product, the peptising effect of the polyacrylate is overcome and a rapid increase in viscosity will be seen.

Dispex® A40 is supplied as a solution at 40% active solids content in water

This new system has proven to be a successful way to incorporate Laponite into a wide range of target applications, including paints and coatings, household products, personal care products and many others.

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Laponite is a registered trademark of Rockwood Additives Limited. All information here is given in good faith but without warranty or guarantee of any kind whatsoever, whether implied or expressed. Freedom from patent rights must not be assumed. This e-newsletter does not form part of the conditions of sale, is of a general nature and should not be used as a basis for a specification.

Rockwood Additives Limited, Moorfield Road, Widnes, Cheshire WA8 3AA, U.K.

Tel:+44 (0) 151 495 2222 – e-mail: help@laponite.com – web site: www.laponite.com

Place of Registration: London, U.K.

Company Registration No.: 4050418

Registered Office: 10 Upper Bank Street, London E14 5JJ, U.K.

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