Choice-HLB emulsifier method

HLB method (hydrophile lipophile balance method) for all types of surfactant, its main methods are: 

1 HLB value of emulsifiers selected 

A specific oil - whether the choice of which water systems can get the best performance emulsifier emulsion, which is the key to preparation of emulsion. The most reliable way is through experimental screening, HLB values can help the screening. Experimental results show that as the O / W type (oil in water type) emulsion of the emulsifier the HLB values often between 8 and 18; as W / O type (water in oil type) emulsion of the emulsifier the HLB value often between 3 and 6. In the preparation of emulsions, in addition to the type of emulsion according to choice for enriching emulsifier, the oil phase of the different nature of the HLB value of emulsifiers have different requirements. And, of emulsifier HLB value should be consistent with emulsified oil phase desired. 

There is a simple emulsion of oil is needed to determine HLB values: visual oil on the surface of aqueous solutions of different emulsifier HLB value of the spreading case, when the emulsifier HLB value of the very large spread of oil completely, with the HLB value decreases, spreading difficult, until the emulsifier solution in a HLB value of oil just does not start, this emulsifier HLB value of approximately the required HLB value of the emulsified oil, this method although the rough, but simple, the results have a certain reference value. 

2 HLB value and the best selection of emulsifiers 

Each has a specific HLB value of emulsifiers, emulsifier is often difficult to meet by a single multi-component system composed of emulsified requirements. Usually a variety of emulsifiers with different HLB value of mixed use, constitute a mixture of emulsifiers, both to meet complex system requirements, and can greatly enhance the emulsification effect. For an oil emulsion - water system, according to the following steps to select the best emulsifier. 

① oil - water system to determine optimum HLB value 

Selected a pair of emulsifier HLB value of the difference between the larger, for example, Span-60 (HLB = 4.3) and Tween-80 (HLB = 15). Prepared in different proportions with different HLB values into a series of mixed emulsifier, with this series of mixed emulsifier systems were made of the specified series of oil and water emulsions to determine the efficiency of the various emulsion emulsion (a stable emulsion can be used to represent time, other stable properties can also be used to represent), and the calculated mixed emulsifier HLB, mapping, can be a bell-shaped curve. The peak of the curve with the corresponding value is the HLB emulsifier HLB value of the specified system required. Clearly, the use of mixed emulsifier HLB value of the most appropriate available, but the emulsifier may not be the best in efficiency. 

The efficiency of the so-called good emulsifier is required to stabilize emulsions specified minimum concentration of emulsifier, the cheapest price. Expensive but required a much lower concentration of emulsifier may also be cheaper than the price, a large concentration of emulsifier efficiency. 

② determination of emulsifier 

Emulsion system in the maintenance of the required HLB value selected under the premise of a few of the emulsifier mixture of multiple choice, so that the mixed emulsifier of HLB values are all determined by the value of the above, specify the system using the emulsion, measured stability, comparing the emulsifying efficiency, until you find a pair of the most efficient emulsifier up. It should be noted that the concentration of emulsifier are not mentioned here, but this does not affect this matching method, because a stable emulsion preparation of the required HLB emulsifier concentration has little value. In the emulsion unstable region inside. When the emulsifier concentration is low or high internal phase concentration only when the impact of this method. 

Methods used HLB emulsifier, HLB value not only to consider the best, should also pay attention to the dispersed phase and dispersion medium, emulsifier and affinity. An ideal emulsifier, not only to blind and strong with the oil, but also with the water phase has a strong affinity. HLB value of the emulsifier with HLB value of the small big mixed emulsifier to form a mixed film with the oil phase and water phase has a strong affinity for taking into account these two requirements. Therefore, the use of mixed emulsifier better than using a single emulsifier. To sum up, decided to designate the system of emulsified emulsifier formulation is required: choose a pair of emulsifiers, in a certain range to change the mixing ratio, obtain the highest efficiency and HLB value, the change in the types of emulsifiers and proportion, but still need to maintain this desired HLB value, until the search was the most efficient emulsifiers. 

3 HLB value of mixed emulsifier ratio 

In the emulsifiers, the use of a suitable number of content available through their respective HLB values and the value of the specified system, obtained the required HLB. For example, vinyl acetate during the O / W type emulsion, the emulsifier dosage is 3%, with SDS, and Span-65 as emulsifier, the HLB value is known SDS 40, Span-65 in the HLB value of 2.1 , emulsion required HLB value when the average was 16.0. 

Span-65 located in the mixed emulsifier in the mass fraction w%, then 40 (1-w%) +2.1 w% = 16, solution of the obtained w% = 63.3%. SDS in the mixed emulsifier in the mass fraction of 36.7%. It can be seen in the vinyl acetate in the O / W type emulsion system, Span-65's with the account for 3% × 63.3% = 1.9%; SDS's use accounts for 3% × (1-63.3%) = 1.1%. 

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