Page 122 - Handbook of Surface Improvement and Modification

7.3 Application data 117

7.3 APPLICATION DATA

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An inkjet ink contained water, colorant, and a dynamic surface active agent. Large
dynamic surface tension differences between the indicated timescales yield an optical den-
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sity improvement in printed images. Management of the surface tension of inks is
required to enable delivery of ink through a printhead in addition to aiding wetting of the
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surface of the substrate to which the ink is applied. The dynamic surface tension of the
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ink can be measured by the hanging drop method. The calculation of the surface tension
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uses the Laplace equation and is implemented in the software of the instrument. Fluoro-
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surfactant (Zonyl FSO) is used in the formulation at the concentration of 0.025%.
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An ink for high-speed printing includes resin, colorant, solvent, and additives. The
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ink can be a flexographic, a rotogravure, offset, or a publication gravure ink. The ink
should have a surface tension equal to or greater than 26 mN/m if the substrate moves at a
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speed greater than 1200 feet/min. The ink surface tension, gravitational forces, and sur-
face-tension-gradient effects (Marangoni flow, which arises during drying) determine ink
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leveling. Leveling is a process of eliminating surface irregularities of a continuous ink
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film under the influence of the ink’s surface tension. It is an important step in obtaining a
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smooth, flat and uniform ink film. The leveling speed increases with increasing surface
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tension of the ink and decreasing ink viscosity. The effect of surface tension on ink
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spreading is opposite to its effect on leveling. To achieve good spreading, the surface
tension of the ink should be as low as possible; for good leveling, the surface tension
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should be as high as possible. In practical applications, a compromise has to be
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reached. This balance of ink properties can be achieved by proper selection of solvents
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which is discussed in the patent.
The surfactant composition useful as wetting agents in aqueous formulations has low
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dynamic surface tension. The composition comprises a dialkylsulfosuccinate compound
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and a branched secondary alcohol ethoxylate compound. This surfactant is suitable to
reduce surface tension of agrochemical, coating, ink, textiles or leather treatment, and
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spray coating formulations. A dynamic surface tension of 45 mN/m can be achieved at a
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concentration of 0.1 wt% of surfactants combination.
The fragrance formulation has a viscosity of 9 cPa or less, a calculated water-octanol
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partition coefficient in the range of -1 to 4; and a surface tension below 25 mN/m. The
formulation is suitable for use in air fresheners, particularly nebulizing scent delivery
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devices. The surface tension is one of the controlling factors for the quality of spray
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delivered by scent delivery device. The surface tension is regulated by selection of carri-
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ers and solvents.
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The nail treatment composition has a surface tension lower than 25 mN/m. A phar-
maceutical formulation contains a volatile, penetrating vehicle; a wetting agent (volatile
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silicone − cyclomethicone); and a non-volatile solvent.
The ink composition comprises a water-dispersible resin and has a dynamic surface
tension of below 35 mN/m and a static surface tension of above 21 mN/m both determined
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at the operating temperature. A mixture of surfactants includes acetylene glycol or
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ethoxylated acetylene glycol and silicone or fluorochemical surfactant. Surfactant mix-
ture comprising an ethoxylated dodecyne and an ethoxylated siloxane works extremely
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well. Such mixture significantly reduced the static and dynamic surface tensions of an