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MSN01 90ml, 120ml dual dispensing package MSN02 40ml, 80ml, 120ml dual dispensing package MSN03 150ml dual dispensing package  
MSN01 dual dispensing package MSN02 dual dispensing pack MSN03 dual dispensing bottles  
MSN04 50ml, 100ml, 130ml, 150ml airless dispensing package MSN05 20ml, 30ml PETG dropper bottle MSN06 15ml, 30ml, 40ml, 50ml, 60ml dual dispensing package  
MSN04 PP airless container MSN05 syringe pump container MSN06 dual dispensing pack  
MSN07 100ml, 150ml nail polish remover bottle MSN08 15ml, 30ml, 50ml acrylic cosmetic jars MSN09 15ml, 30ml, 50ml acrylic cosmetic jars  
MSN07 nail polish remover MSN08 acrylic cosmetic jars MSN09 acrylic cosmetic jars  
MSN10 15ml, 30ml, 50ml acrylic cosmetic jars MSN11 15ml, 30ml, 50ml acrylic cosmetic jars MSN12 15ml, 30ml, 50ml acrylic cosmetic jars  
MSN10 acrylic cosmetic jars MSN11 acrylic cosmetic jars MSN12 acrylic cosmetic jars  
Dual Dispensing Packages

By Victor Suben, P. E.

In recent years, many new products have been developed that require mixing two ingredients. Because of the nature of these products, the mixing must occur at the time of application or use and not before. Premature mixing would result in either a product that could not be used at all, or a product that would not be effective in achieving its intended purpose.

Most of us are familiar with two-part epoxies and the various means of dispensing and mixing the epoxy and the hardener. The earliest dispensing/mixing systems consisted of two tubes and one or more mixing sticks packaged in a folding carton. In this format, equal volumes or weights of each part would be dispensed onto a flat surface, and then they would be mixed with the stick until a uniform consistency or color was attained. At that point the epoxy was ready for application.

Over time, other dispensing systems were developed. Most notably these consisted of two syringes mounted side-by-side. In these units, the plungers were attached to a common bar so that when the bar was pressed, both plungers moved through equal distances. The advantage of these units is that equal volumes of both parts of the product are dispensed, regardless of any differences in viscosity or specific gravity.

Modern hair coloring products also require that two ingredients be mixed together at the time of application. However, for hair coloring products, equal amounts of the two ingredients cannot be used. Thus, it was necessary to find a means of dispensing the ingredients in the correct proportions to permit development of the desired color.

In some cases proportional dispensing was achieved by means of two tubes of different sizes encased in a single folding carton. Another version of this type of dispensing system consists of a two compartment container with the compartments separated by a thin membrane. The compartments are usually of different sizes so that each one contains the quantity of ingredient required for mixing in the correct ratios.

Upon squeezing the tube, the membrane is broken, and with further kneading of the sealed tube, the two ingredients are mixed together. The product that is finally dispensed has been mixed in the correct proportions to make it efficacious. The advantage of this type of system is that regardless of different specific gravities or viscosities, the correct ratio of the two parts of the product is always maintained, and the two parts are not mixed until the product is ready for use.

During the past 15 years, or so, a variety of skin care products have been developed that require mixing together two different ingredients. In many cases the mixing had to be done on a one-to-one basis. In these products it was not uncommon for the individual ingredients to have different viscosities and specific gravities. Consequently both sections of the dispensing package needed to contain an equal volume of the product.

Over the years, various packaging configurations were reviewed to determine whether they could meet the requirement that the two parts of the product could be dispensed in equal amounts. These configurations mainly came in the form of flexible tubes and dual-chamber pumps.

Basically the dual dispensing tubes came in two forms: one was a tube within a tube, and the other consisted of two side-by-side tubes encased in an outer tube.For both types of dual dispensing tubes, both tubes were connected to the shoulder that was common to both. Further, each tube was connected to its own orifice in a unique manner, proprietary to each manufacturer. The side-by-side configuration provided for equal volumes of each ingredient. By pressing the outer tube, it was presumed that an equal amount of each ingredient would be dispensed. Unfortunately, this configuration did not consider the dispensing characteristics when the two ingredients had significantly different viscosities. Thus, it was not unusual to have one ingredient spurt out of the orifice while the other ingredient had to be forced out more much more slowly. In addition, it proved to be difficult to compress the outer tube in such a way that both tubes would experience the same amount of pressure at the same time.

In some ways, the tube-within-a-tube concept more nearly hits the mark. By pressing the outer tube in this configuration, product would be dispensed from both tubes. By adjusting the ratio of the tubes' volumetric capacities, it would be theoretically possible to have the two ingredients dispensed in the correct ratios. However, when generic versions of this configuration were tested, they did not perform in a completely satisfactory manner. The apparent reason for the poor performance seemed to stem from the fact that the two ingredients had significantly different specific gravities and viscosities. For this configuration to work satisfactorily, the size of each of the two tubes would have to be adjusted for each set of ingredients. In this version, there is no such thing as "one size fits all." In order to work satisfactorily, the sizes of the tubes would have to be adjusted for each product to be dispensed.

Researchers have found that a very effective self-tanning product required mixing together two ingredients at the time of application. Also, for a variety of reasons, the most desirable packaging system for such products was a mechanical pump dispenser. For the reasons cited above, it was found that the dual tube configuration did not work satisfactorily for this class of products.

Various mechanical pump dispenser manufacturers developed dual dispensing systems. Most of these incorporated two bottles locked together with a tongue and groove arrangement. Each bottle had its own mechanical pump dispenser. In most cases, the pumps had dip tubes and common actuators. Some of the actuators enabled mixing of the two ingredients within a chamber behind the orifice, while others dispensed the product through two separate orifices.

It was found that systems with mixing within the actuator allowed a small quantity of the mixed ingredients to remain inside the orifice at the end of the dispensing operation.Although the quantity of the mixed product was small, it did mean that the product dispensed during the initial one or two strokes had to be discarded. The system that required mixing outside the actuator obviously did not have this problem. However, a problem common to both systems was that in some instances the product left inside the actuator would dry out and harden. Thus, a small quantity from the first one or two dispensing strokes had to be discarded. A much more significant problem than that was the fact that, in many instances, ingredients with different viscosities had to be dispensed in equal amounts.

There are usually slight variations between one pump and another of the same model from the same manufacturer.Even with a single product, the same model pumps often have variations in the amount of product dispensed per stroke and in the number of strokes to prime. When dispensing a single product from one package, it does not matter if it takes five or six strokes to prime or if it dispenses 75 or 85 microliters per stroke. This variation does become significant when both pumps need to prime within exactly the same number of strokes and the amount of product from each must be exactly the same.

One system available for several years is made up of two syringes mounted side-by-side in an outer container. The only commercial use of this system that I have seen has been for the dispensing of a toothpaste product. This system could probably dispense liquids with a low viscosity as well as high viscosity creams.

Pfeiffert has recently developed a system that employs dual piston packages, coupled with standard bellows pumps. Piston packages are suitable for dual dispensing because, like the syringes mentioned above, they do not require priming. In order to function properly, the containers for piston packages need to have the inside walls perfectly cylindrical and as smooth as possible. According to Pfeiffer, it has also developed a manufacturing system in which they can produce containers that are perfectly cylindrical and that do not have a draft angle on the inside surfaces.

Piston packages are comprised of a pump, a container, a piston and a plug with a vent hole. In most cases, the pump is attached to the container, the product is filled from the bottom, and the piston is inserted and forced up until it is contact with the product. Then, the vented plug is inserted into the bottom of the container. The pistons are usually made of polyethylene, and when viewed from the top, they are circular. When viewed from the side, the piston has a shape of a shallow "u." The upper leg of the "u" is usually quite flexible and serves as a "wiper," while the stiffer lower leg acts as an air seal.

Filling the containers from the bottom ensures that the product is always in contact with the inlet to the pump; when filling from the top, care must be taken to ensure that the product is filled to a level that the product will be either close to or in contact with the inlet to the pump. In operation, each stroke of the pump creates a vacuum inside the container. This vacuum causes either the product or the air in the head space to enter the pump and be dispensed from it. Operation of the pump also reduces the pressure inside the container. The pressure differential between the inside of the container and the surrounding atmosphere allows air to enter through the vent hole in the base of the package, forcing the piston upward. If air gets past the piston, the system will stop dispensing product once the air bubble gets to the pump inlet. Therefore, it is important in such systems to have a very smooth and cylindrical wall inside the container and a fairly stiff sealing ring on the piston. Because piston packages are volumetric dispensers, the two components of the product can have different viscosities. So far these packages have only been used for creams, lotions and gels.

Dual dispensing systems become more complicated when the two products must be dispensed in different ratios. Depending on the required ratio of the product, the piston package might be a suitable alternative. For this option to work successfully, the two pumps would have to have different dispensing characteristics (i.e. output per stroke). Also, although the containers might have the same size, the piston of one of the containers would need to be at a higher level than in the other container.

For dispensing products that require a ratio other than one-to-one, there are also conventional (i.e. dip tube) pump systems that incorporate a small container suspended inside the larger one. Fluid flows through the dip tube into the pump body. The small container inside the larger one is connected to an orifice in the pump body. As the fluid flows in the pump body, the reduced pressure adjacent to the orifice allows the fluid from the small container to flow into the pump body and mix with the fluid from the larger container.

"one size fits all." Thus, each new product that requires a ratio of one ingredient to another will probably require a unique packaging configuration. The most successful dual dispensing packages at this time are the dual syringe and the dual piston packages.

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