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b. Chemical Energy: |
A properly choosen polar additive is used in the preparation of SMECTONE CLAY gets to initiate the separation of the minute ultimate particles. Most useful of the general-purpose additives are the low molecular weight alcohols such as methanol, ethanol and other high polar liquids suggested below. When these alcohols are anhydrous, the ration of alcohol to the SMECTONE CLAY gellant is critical, since the peak get strength versus alcohol contain 5% water. For this reason 95% alcohols are always recommended to allow for slight variations in the actual ration of alcohol to SMECTONE CLAY gallants. |
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| Type of Polar Additive |
Amount required based on
Weight of dry SMECTONE CLAY gellant |
| Methanol/Water – 95% / 50% 33% |
33% |
| Propylene Carbonate – 100% |
33% |
| Ethanol/Water – 95% / 5% |
50% |
| Acetone – 100% |
60% |
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The polar additive acts as a wedge to open up the clay platelets and makes readily available for developing maximum gellation. Use of a polar additive is a must to ensure against change in gel strength and obtain best gelling results.
In the preparation of pregels the level of SMECTONE CLAY additive may vary, but 10% is suggested for easy handling. Initially, SMECTONE CLAY is mixed with the major organic compounds followed by the addition of right amount of the polar additive. For best results high shear or high speed dispersion methods are also used for optimum results when using chemicals energy to prepare SMECTONE CLAY gels. |
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MANUFACTURING PROCEDURES WITH SMECTONE CLAY: |
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There are three basic ways to add SMECTONE CLAY rhelogical additive regardless of the manufacturing equipment in use:
• In Situ addition
• Pregelled addition
• Predampening addition
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| a. In Situ addition of SMECTONE CLAY: |
This approach is most appropriate with resins having good wetting characteristics and/or where development if thixotropic structure in the grind base is acceptable. SMECTONE CLAY rheological additive is incorporated as a dry powder. Polar additive is also added as described above.
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| b. Addition of Pregelled SMECTONE CLAY: |
Pregelled SMECTONE CLAY consists of SMECTONE CLAY dry powder, polar activated, partially dispersed and gelled in a solvent. It is required for poor wetting resin systems and/or non-thixitropic mill bases. SMECTONE CLAY is pregelled generally on high-speed dispersion equipment as follows |
| Add |
Proportion |
Procedure |
| Solvent |
(87 parts) |
mix |
| SMECTONE CLAY Additive |
(10 parts) |
mix 30 mts. |
| Polar Additive |
(3 parts) |
mix 10 mts. |
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Pregelled SMECTONE CLAY is used to ensure that the rheological additive is fully wetted out and all the polar activator reaches the SMECTONE CLAY rheological additive. A poor wetting resin interferes with the wetting process, which is essential for a proper gel.
Pregelled SMECTONE CLAY still needs additional shear for full gel development and must be included in the subsequent mix step. |
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c. Predampening addition of SMECTONE CLAY:
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In predampening addition of SMECTONE CLAY the weighted amount SMECTONE CLAY is put into a container and 33% of 95/5 Methanol/water (or any other polar additive) based on the weight of SMECTONE CLAY is added. This is mixed with a spatula or a paddle for 5 to 10 minutes. The polar additive is completely absorbed by the SMECTONE CLAY in a slightly dampened powder. The predampened SMECTONE CLAY is then added to the system in a base solvent to be gelled followed by appropriate mill grinding or high shear stirring. |
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| d. Post Addition of polar Additives |
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In cases where gel formation is required in low viscosity organic liquids, and where only high shear stirring is used, post addition of polar solvent is almost always preferable, as pregelled SMECTONE CLAY may lead to lumpy gels. In these cases, it is better to add SMECTONE CLAY to the liquid while stirring and agitate long enough to disperse the SMECTONE CLAY particles smoothly. Finally, the right proportion of 95% alcohol is added while the stirring is operating. This technique ensures smooth and high efficiency ‘lump free' gels.
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