Emulsifiers

Chapter 1: What is an Emulsifier?

An emulsifier is an emulsion device used for colloidal dispersion of liquid droplets of immiscible liquids in the presence of an emulsifying agent. It enables the combining of non-soluble solutions or liquids that would normally separate during mixing. In emulsification, a liquid is broken down into droplets or particle sizes using various types of force, such as a rotating propeller mixer, vacuum, rotor stator, or high shear mixer. The reduction process reduces the sizes of droplets to less than a micron (µ) to create a very fine emulsion. Emulsifiers use scalable high pressure to produce the proper droplet sizes.

The various types of emulsifier machines or vacuum emulsifying mixers can mix, disperse, homogenize, emulsify, and aspirate viscous ingredients and non-soluble liquids. The system of an emulsifier is without dead corners and is powered by electricity. Emulsifiers can function like a vacuum and heat or cool its surroundings. Creams, liquids, lotions, ointments, medications, and liquid creams are blended using an emulsifier due to their immiscibility.

Chapter 2: The Process of Emulsification

The goal of emulsification is to achieve the smallest possible droplet size such that immiscible materials can form an emulsion. As more energy is applied to a mix, smaller droplets are produced in order to create a fine emulsion. A proper emulsion process can determine the consistency and quality of a product. Although emulsion can be completed using various synthetic substances, a mixer is more efficient in producing the needed droplet size.

The emulsion process is a two-phase system where one phase, the internal or dispersed phase, is changed into small droplets to be dispersed in the other phase, the external or continuous phase. Energy is required to prepare the emulsion and create the two-phase system.

The goals of emulsification are:

• Physicochemical Stability – Emulsification determines the characteristic structure of a product.
• Sensory Properties – Emulsification determines the appearance, texture, and flavor of a product.
• Surface – The careful mixing of two immiscible, non-soluble substances produces an even, smooth surface.

The process of emulsion is referred to as emulsification and involves an immiscible liquid being dispersed with another immiscible liquid. It is unlike colloidal solutions since it involves the mixing of liquids. The process of emulsification includes chemical, physical, and mechanical processes.

Mechanical emulsification is based on three theories:

• Surface Tension Theory – Surface tension theory postulates that emulsification takes place when there is a reduction in the interfacial tension between the dispersed phase and the dispersion medium.
• Repulsion Theory – In repulsion theory, the particles of the dispersed phase remain dispersed in the dispersion medium, which is caused by repulsion force. A film covers one phase, which makes globules of that phase repel other globules.
• Viscosity Modification – Emulsifying agents can increase the viscosity of a medium causing the globules of the dispersed phase to remain dispersed in the dispersion medium.

Types of Emulsion

The types of emulsions are simple and complex where simple emulsions involve dispersing oil in water or water in oil. If the dispersed phase is water and the dispersion medium is oil, the emulsion is referred to as being water in oil or W/O. The reverse is true when the dispersed phase is oil and the dispersion medium is water, notated as O/W.

Complex emulsions, known as multiple emulsions, are oil and water and water and oil emulsions that are stabilized by surfactants. They are notated as O/W/O and W/O/W, which are double emulsions of O/W and W/O.

Emulsifiers

Emulsifiers are emulsifying agents that are used to stabilize the emulsion by increasing the kinetic energy and are more or less soluble in water and have hydrophilic water-soluble parts and hydrophobic parts. Types of emulsifiers include Lecithin, soy lecithin, sodium phosphates, monoglycerides, diglycerides, and sodium stearoyl lactylate.

Emulsification Process

Although emulsification is commonly used in the preparation of foods, it extends far beyond those activities into the manufacture of several products including pharmaceuticals and paints. It allows engineers to create different products by combining ingredients and liquids in unique and unusual ways.

• Emulsifier – The key to emulsification is the emulsifier, which is a surfactant that reduces the surface tension of liquids. Emulsifiers are carefully chosen to match the chemical properties of the ingredients to be combined such that they don’t precipitate out of the mixture.
• Force – As may be expected, some type of force is necessary in order to blend and mix the liquids. There are a wide range of emulsifiers that provide the necessary energy and vary from blenders to powerful industrial machines and mixers.

  An essential part of the emulsion process is stabilization, which is especially true for pharmaceuticals. Most emulsions are thermodynamically unstable and will separate over time. This aspect of emulsions necessitates the proper choice of an emulsifier to ensure long lasting stability.

  The use of force or energy is due to emulsification rarely being a spontaneous process and requires energy in the form of mechanical shear that is provided by a mixer or blender. The final droplet size is dependent on the amount of energy that is applied. Paddle mixers are used when the droplet size is greater than 10 µ. To make smaller droplets, high shearing is required using rotor stator mixers.

Lipophilic and Hydrophilic Emulsifiers

Unlike the emulsifying process that is used to blend two immiscible liquids, lipophilic and hydrophilic emulsifiers are used to remove excess emulsifiable penetrants from the surface of processed parts. These types of emulsifiers do not contain surfactants, which makes them ideal for removal of excess penetrants while leaving penetrants on the surface of a part.

Lipophilic emulsifiers combine with oil-based penetrants to be removed from the surface of a part using a water spray. They work by diffusing into the post emulsifiable penetrant and are drained immediately from the part. The rapid application and removal is necessary to prevent over emulsification and removal of the penetrant.

Hydrophilic emulsifiers are supplied in concentrate form, are diluted in water, and use detergent action. Prior to applying the hydrophilic emulsifier, parts are rinsed in water and then immersed in agitated tanks of the hydrophilic emulsifier, or the emulsifier is sprayed on. After the application of the emulsifier, parts are rinsed with water.

Laser Diffraction

Laser diffraction is used to measure the size of droplets produced in the emulsion process. It helps define the flavor of food products and the stability, appearance, and processability of an emulsion. Laser diffraction is a very common technique and is based on the idea that the angle of laser light diffracted by a particle corresponds with the size of the particle. When a sample has different particle sizes, a diffraction pattern is seen. An analysis of the pattern helps determine the size of the composition. Once the diffraction pattern is determined, an algorithm is used to compare the measured values and particle size distribution.

Chapter 3: Types of Emulsifiers

The emulsification process requires the use of some form of energy. Although the process of emulsification follows certain chemical steps, the types of mechanisms and energy for the process take many different forms and involve the use of vacuums, ultrasonic waves, and high powered, highly efficient equipment.

Rotor Stator Mixers

The emulsification process depends on breaking down liquids into small droplets in order for liquids to mix. Rotor stator mixers are used to produce high speed dispersion. In the rotor stator process, the rotor turns at high speed and acts like a centrifugal pump that pulls in material and breaks it into smaller particles.

Rotor stator mixers operate in two modes, which are batch and continuous where the blending process is continuous in the continuous mode while the batch mode involves the use of pumping power and shaft power. The process involves pumping the emulsion phase through the narrow gap in a perforated cylinder or stator. The rapidly rotating rotor supplies the force to make the droplets smaller.

The design of rotor stator mixers is to create high stress and intense turbulence. Energy from the rotor gets dissipated inside the stator, which leads to high local energy dissipation that is unlike conventional mixers. Rotor stator mixers generate shearing stress, elongation stress, and turbulence cavitation to create extremely small particle sizes.

Micropore Emulsification

Micropore emulsification produces tighter droplet sizes and emulsions with significantly high stability. The process can be used with high viscosity ingredients to mix reliable and reproducible emulsions. The two phases are introduced to each other in a highly controlled process. The dispersed phase enters through pores in a stainless-steel membrane that forms perfectly spherical droplets into the continuous phase.

The controlled shear causes the droplets to deform and detach from the surface and form droplets of the necessary predetermined size. The control of droplet size and movement ensures that batches are perfectly mixed with minimal waste.

Ultrasonic Emulsifier

Ultrasound acoustic cavitation disrupts oil and water droplets for the formation of O/W and W/O emulsions to produce droplets in micron and nano sizes. The very small droplet size makes it possible for droplets to rapidly penetrate cells. Nano emulsions are necessary for the manufacture of coatings, paints, and polymers and are more stable and do not have sedimentation, coalescence, or flocculation.

The process of ultrasonic emulsification is a form of extremely vigorous mixing that speeds up the process. It is a powerful method that completely disperses one liquid into another and neither liquid reverts back to its original properties. Ultrasonic emulsification is a high-tech method of mixing that uses a surfactant to assist in the emulsification process.

High Pressure Homogenization

High pressure homogenizers are also capable of producing nano sized droplets. In the process, emulsion phases are pumped together under high pressure through a small volume orifice. The phases are placed in a tank where pressure is applied to force the liquid through an orifice or membrane that has a narrow slit. The action causes shearing and cavitation that homogenizes the phases. In some instances, the stream is directed at a blade, ring, or plate where the sample collides at high speed.

Unlike ultrasonic emulsifiers that are unable to process volumes of products, high pressure emulsifiers are capable of thoroughly processing large volumes of liquids, which is the reason they are used in the dairy industry. Additionally, high pressure homogenizers allow for changes in the process stream.

High pressure homogenizers are very expensive with the least expensive versions costing approximately $10,000. It is for this reason that they are used for high volume production. In order to prevent contamination, a necessity in dairy product production, high pressure emulsifiers have to be thoroughly and completely cleaned after every use.

There are several varieties of high pressure homogenizers, which necessitate careful consideration during the selection process. One of the variations in the types is batch and continuous processing since not all high pressure emulsifiers are able to do both. Different high pressure homogenizers are capable of accommodating a range of sample sizes. The selected high pressure homogenizer must be capable of handling the sample size of the industry where it will be used.

Homogenization and emulsification are similar processes that are used to create solutions with different chemical and physical properties. The difference between the processes is the nature of the solution they are processing. Homogenization is the mixing of two miscible liquids while emulsification is the mixing of two immiscible liquids.

High Shear Mixers

High shear mixers are rotor stator mixers, shear reactors, and shear homogenizers that are used for emulsification. They have high rotor tip speeds, high shear rates, localized energy dissipation rates, and a higher power consumption rate than ordinary mixers. Shearing is the stress that the blades or impellers of a mixer place on a liquid. The rotor directs a liquid outward to the stator, which creates a shear in the process. Variable speeds of the rotor make it possible to tailor the amount of shearing energy required to meet the needs of an application. The term shear is a reference to the stress placed on immiscible liquids by the mixing blades or impellers.

Unlike high pressure homogenizers that place pressure on liquids to cause emulsification using high amounts of energy to create pressure for droplet size reduction, high shear mixers use shearing action to accomplish the same result. Droplets are efficiently and effectively reduced to the submicron level.

Inline Emulsifier

An inline emulsifier is a type of high shear mixer that has a rotor and stator. As with rotor stator mixers and high shear mixers, the rotor rotates at high speed to draw the immiscible liquids through the stator where the liquids endure high shearing forces to disperse small droplets throughout the liquid. The result of the process is a highly stable emulsion.

Inline emulsifiers come in several sizes and configurations to fit the needs of a range of applications. Regardless of the many different types of inline emulsifiers, all types have certain basic and common characteristics

• Shear Rate – The shear rate for an inline emulsifier is between 10,000 rpm up to 50,000 rpm.
• Stages – The inclusion of multiple stages in an inline emulsifier makes it possible to have a more thorough emulsification process. Multiple shear forces are applied to the emulsion.
• Cleaning – Inline emulsifiers have a clean in place system for easy cleaning of the mixing chamber to reduce downtime and increase productivity.
• Efficiency – The key to the success of inline emulsifiers is their efficiency since they are a continuous emulsification process. They have an emulsification rate of over 90% to ensure cost-effective waste reducing processing.

Multi Shaft Mixer

Multi shaft mixers have more than one shaft and can include two, three, or four shafts. Their mixing elements can be blades, paddles, or have a helical shape, which are used in accordance with various applications. As with all forms of emulsification equipment, multi shaft mixers supply sufficient power to change droplet size for the emulsification process. They can handle a wide range of immiscible liquids efficiently and effectively and can be customized to the needs of any application.

A common design of multi shaft mixers is the inclusion of a disperser and rotor stator in a single mixer. This configuration speeds up the emulsion process where the disperser begins the process while the rotor stator improves the texture of the emulsion.

Vacuum Emulsifier

With a vacuum emulsifier, materials are placed in a mixing tank that has fixed impellers with holes for thorough mixing. During the emulsion process, the blades of the impellers rotate forward and reverse at variable speeds. The high-speed mixing process moves the materials up and down using the forward rotation of one impeller to move materials up while the reverse motion of the other impeller moves material down. The completed emulsion is removed from the mixing tank by centrifugal force.

The vacuum in the mixing tank is created by a vacuum pump that forces air out. A sensor monitors the pressure on the liquid to keep it in a normal state. The vacuum improves the performance of the mixer to produce exceptional mixing results. Controlling the environment of the mixing using a vacuum prevents aeration, protects the impellers, and produces void free mixed products.

Chapter 4: Uses for Emulsifiers

Emulsifiers are a critical part of several industrial operations for the mixing of liquids for the production of various products. In manufacturing, there are products that require ingredients with different densities to be mixed together, which can only be accomplished with an emulsifier. Included in the emulsification process is an emulsifier that keeps the ingredients stable until their final use.

One of the restrictions on the use of emulsifiers in the food, pharmaceutical, cannabis, and cosmetic industries are the regulations of the Food and Drug Administration (FDA), which oversees any commercial products for general public use. Any type of substance or material used to produce such products has to receive FDA approval. Two acceptable emulsifiers for the food industry are sorbitan esters and polysorbates that come from natural fatty acids.

Food Industry

The food industry makes the greatest use of emulsifier machines and emulsifiers since several food products exist in an emulsified form such as dressings, sauces, spreads, dips, creams, and drinks. Emulsifiers keep ingredients stable to help products maintain their shelf life. The use of the right surfactant helps materials remain mixed in a homogeneous state. Emulsifiers are used in the meat industry to cut and emulsify meat to make sausages.

Pharmaceutical Industry

The pharmaceutical industry uses emulsion technology to make palatable medicines by more effectively dispersing their ingredients. Without emulsion, drugs would be too bitter to take and work improperly since dosages would be inconsistent. Emulsion blends and mixes ingredients such that medicines are produced in the proper proportions and dosages.

Cosmetics Industry

The key to emulsions in the cosmetic industry is to ensure that products have the right appearance and can be applied evenly. Emulsification mixes and breaks apart the substances for beauty products into extremely small droplets to make it possible to produce cosmetics that have a smooth consistency and can be easily absorbed. Since emulsification radically decreases the particle size of cosmetics, products are easier to absorb, are more stable, and last longer.

Cannabis Industry

The cannabis industry is growing rapidly due to the use of emulsification to improve the taste of their products. Emulsification ensures the consistency of products by reducing the size of the cannabinoid molecules, which makes it easier for the body to adsorb the product and delivers a uniform amount of active ingredients.

Paint Industry

Paint is made up of pigment that gives it color, a binder, and a solvent that makes paint liquid and easy to spread. Emulsion is necessary for the manufacture of paint because the three ingredients are unable to fully blend. In the process, the pigment and binder form small droplets that are spread into the solvent. In this case, the pigment and binder are the oil while the solvent is the water.

When paint is applied to a surface, the droplets of pigment and binder are applied to the surface. During the drying process, the solvent evaporates or dries and the droplets of pigment and binder get closer together and eventually stick together to form a solid, colorful layer. This process is possible due to the emulsion of the paint.

Industrial Lubricants

Metalworking fluids and industrial lubricants are O/W emulsions. The use of emulsifiers makes it possible for metalworkers to have the lubricating properties of oil and the cooling properties of water. Anionic and nonionic emulsifiers are the most common types used in metalworking while cationic ones are rarely used because they are unstable in alkaline solutions.

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Chapter 5: Types of Emulsifiers Used in Emulsification Equipment

Emulsifiers are an essential element in the emulsification process. The mixing and blending of immiscible substances require the use of an emulsifier that fits the chemical properties of the materials to be mixed. In the process, the emulsifier reduces the interfacial tension of the materials and forms a film on the surface of the droplets. It prevents droplets from aggregating and helps maintain a uniform emulsion.

Anionic Emulsifier

Anionic emulsifiers ionize in water to form hydrophilic groups. They are used for alkaline or neutral conditions but cannot be used with acidic compounds. Anionic emulsifiers can be used with nonionic emulsifiers. They are found in laundry detergents, handwashes, kitchen cleaners, and body wash and are the most widely used emulsifier. Their industrial use includes architectural coatings, industrial coatings, and water-based coatings.

Cationic Emulsifiers

Cationic emulsifiers are ionized in water to form cationic hydrophilic groups and used with acidic compounds. They are positively charged and used to emulsify water in oil-based coatings. Cationic emulsifiers are used in the manufacture of wood finishes, metal coatings, and oil-based coatings.

Nonionic Emulsifiers

Nonionic emulsifiers are the second most widely used emulsifier. The molecules of a nonionic emulsifier have no charge. They are used to emulsify oils and water coatings, emulsion polymerization, and as a dispersing agent in varied applications. Nonionic emulsifiers are used in cleaning, personal care products, and disinfectant products. They do not ionize in water.

Sorbitan Monooleate

Sorbitan monooleate is used in food processing. It is a low polyol nonionic emulsifier that is in the lipophilic group of emulsifiers. Sorbitan monooleate is used as an additive for medicines and food and is soluble in water and ethanol. For the production and processing of food, medicines, cosmetics, and textile printing, sorbitan monooleate is used as a stabilizer, dispersant, and emulsifier.

Lecithin

Lecithin is widely used in the food industry and is extracted from soybeans, egg yolks, milk, sunflower seeds, and rapeseeds. It is combined with emulsifiers to create a mixed emulsifier to assist in stabilizing the emulsion process. As a multipurpose emulsifier, lecithin has a wide range of characteristics. It is sold in liquid, granule, powdered, and gel capsule forms.

Polysorbates

Polysorbates are made from the sugar alcohol from fruits. It’s yellow in color and has viscous properties after being treated with ethylene oxide.

Mono and Diglycerides

Known as partial glycerides, mono and diglycerides are fatty acids found in food and are exceptionally soluble in dense solvents.

Sodium Stearoyl Lactylate

Sodium stearoyl lactylate is made from sodium salt and is a FDA and EU approved natural emulsifier.

Chapter 6: The Best Emulsifiers

Sonolater from Sonic Corporation

The Sonolater is a high-pressure emulsifier that achieves extremely small droplet size using fluid acceleration, inline cavitation, and turbulent flow. It is part of a complete system that includes a positive displacement pump, electric motor, and PLC controls. The Sonolater’s fixed orifice and blade are designed to create extreme turbulence to break down oil phase droplets or deagglomerate solids in a liquid medium. It can be customized to fit the needs of any production operation.

Vacuum Emulsifying Mixer from Makwell

The vacuum emulsifying mixer from Makwell has a high-speed rotor and stator. As the rotor and stator rapidly spin inside the homo-head, a pressure differential is created between the top and bottom of the mixer. The material passes through the homo-head and is sheared, broken, mixed, and emulsified. When the upward force stops, the emulsified material pours out of the top of the head and is brought back by downward pressure of the blades. The vacuum system ensures smooth operation to prevent bubbles.

High Shear Batch Mixer from Silverson

The high shear batch mixer from Silverson emulsifies, homogenizes, solubilizes, suspends, disperses, and disintegrates solids. The mixer has a rotor stator work head that cuts processing time by 90% to improve quality, product consistency, and process efficiency. The high shear batch mixer from Silverson can process up to 8000 gallons (30283 L) to reduce particle sizes, and create highly stable emulsions. The advantage of the high shear batch mixer from Silverson is its multistage mixing and shearing action as materials are drawn through the work head.

Inline High Shear Mixer from Ross

The inline high shear mixer from Ross is used for reducing particle sizes and droplet sizes to emulsions for creating scalable and repeatable products. It consists of a single, dual, or four stage rotor stator that mechanically shears material as it passes by the stator. The inline high shear mixer from Ross is mounted on the floor or a platform and material is gravity fed into the mixing chamber. The rotor produces shearing force by rotating at speeds up to 3000 to 4000 ft/min and releases the mixture through the holes in the stator. It can handle high viscosity materials without the assistance of a pump system.

Emulsifier and Inline Homogenizer Mixer from PerMix

The emulsifier and inline homogenizer mixer from PerMix is a high shear mixer for inline continuous operation. The design of the emulsifier and inline homogenizer mixer from PerMix makes it easy to fit it into existing production lines with the use of inlet and outlet connections. In the case of low viscosity liquids, it can pump the material without the use of an additional pump. Products can be processed in a single pass or be circulated for multiple passes for better product quality. The design of the emulsifier and inline homogenizer mixer from PerMix radically cuts processing time to increase efficiency and lower costs.

Chapter 7: Problems with Emulsification

Due to the nature of the emulsification process, there is always the possibility of problems. The purpose of an emulsifier is to create a stable emulsion. The success of the process depends on the composition speed and the concentration of the emulsifiers. The destabilization of an emulsion can be caused by coalescence, sedimentation, Ostwald ripening, creaming, flocculation, aggregation, and phase inversion.

Ostwald Ripening

Ostwald ripening is when small particles in a solution dissolve and deposit on larger particles to reach a thermodynamically stable state. Molecules on the surface of particles are more unstable and go into solution shrinking, increasing the number of free molecules in a solution. Over time, the emulsion becomes unstable and goes into phase separation. Ostwald ripening most often occurs in water in oil emulsions where oil molecules diffuse through the water phase and join larger oil droplets.

Coalescence

With coalescence, the droplets merge to ever larger droplets until the oil and water phases are separated. Coalescence happens due to an insufficient amount of emulsifier, precipitation of water soluble emulsifiers, too high a concentration of base or acid, or the use of anionic and cationic emulsifiers in the same product. It can also happen when the wrong emulsifier is used.

Flocculation

Flocculation occurs when droplets clump or stick to each other to form flocci. In some processes, clumping is good and causes material to precipitate. In emulsions, flocculation leads to a poor emulsion. The process can be reversed by agitation, increasing the concentration of the emulsifier, or adding a higher hydrophilic lipophilic balance (HLB) emulsifier.

Sedimentation

Sedimentation or creaming is where less dense oil droplets rise to the top of the emulsion and a fatty cream appears. There are various causes to the problem such as the oil or water phase being too large compared to the water or oil phase, small dispersed droplet size, or the viscosity of the continuous phase is too low. In each instance, adjustments can be made to correct the problem.

Conclusion

• An emulsifier is an emulsion device used for colloidal dispersion of liquid droplets in immiscible liquids in the presence of an emulsifying agent. It enables the combining of non-soluble solutions or liquids that would normally separate during mixing.
• The various types of emulsifier machines or vacuum emulsifying mixers can mix, disperse, homogenize, emulsify, and aspirate viscous ingredients and non-soluble liquids.
• The goal of emulsification is to achieve the smallest possible droplet size. As more energy is applied to a mix, smaller droplets are produced in order to create a fine emulsion. A proper emulsion process can determine the consistency and quality of a product.
• The types of emulsions are simple and complex where simple emulsions involve dispersing oil in water or water in oil. If the dispersed phase is water and the dispersion medium is oil, the emulsion is referred to as being water in oil or W/O. The reverse is true when the dispersed phase is oil and the dispersion medium is water, notated as O/W.
• The emulsification process requires the use of some form of energy. Although the process of emulsification follows certain chemical steps, the types mechanisms and energy for the process take many different forms and involve the use of vacuums, ultrasonic waves, and high powered, high efficiency equipment.

Leading Manufacturers and Suppliers