Manufacturing Single-Serve Bottles in HDPE

Dairy products, fruit juices, fortified drinks in single serve bottles are part of one of the most rapidly growing sectors in the drink packaging industry. Actually, in many of the markets such as Japan, Europe and South America, pourable yogurts are, for example, becoming more and more popular as they are much easier to consume than thicker yogurts usually eaten with a spoon and thanks to the general perception of good health associated with dairy-based drinks. The companies operating in this market segment differentiate strongly aiming at various consumer sectors and niches. Some concentrate on the health and active lifestyle aspect, on desserts, or on a high quality product for adults and of course on products for kids.
The large part of this single-serve bottles are made from HDPE. In this production process there have been some interesting developments over the last year. I know, what I tell you today, is not all brand new, but I thought the recent developments interesting enough to relate them.

Besides the above mentioned industries the HDPE bottle also is very popular with the pharmaceutical industry.

Compression Blow Forming
Amcor Rigid Plastics is producing single-serve bottles using compression blow forming (CBF) technology, making it the first company to use a CBF machine on a commercial scale. The high density polyethylene bottles are blown on a CBF machine developed by Sacmi Imola S.C.

Left: The CBF process starts with upward extrusion of a “dose”. Right: The dose is sliced off by a rotating tool and deposited in a compression molding cavity on another wheel.

CBF machines combine elements of compression moulding and blow moulding in a continuous rotary process. CBF uses an integrated in-line sequence that does not require station-to-station transfer. Material is extruded, cut and transferred into a compression cavity. A preform is produced, and bottles are then pre-blown before the blow mould cavity closes over the preform. Then, the mould cavity closes and the bottle is blown.

Left: After compression moulding, the preform is immediately pre-blown to release it from the cavity/core and ensure uniform material distribution. Right: Final blowing occurs in the same mold station as the previous two steps, with no transfer of the preform. Stretching can be added.

Instead of using a manifold for melt distribution, an extruded shot of resin is transferred directly into the compression mould, giving producers more control over the quality of the container. Eliminating a manifold also eliminates differences in temperature, so there’s less chance of particulate contamination, resin burning, and other defects, like the black specks seen with injection blow moulding

Each bottle is leak tested before leaving the machine. Left: The next step in the three-stage, in-machine QC system is an IR camera system that checks for dimensional varitiations and contamination on or in the bottle wall. Right: The final in-machine QC step is an atmospheric plasma treatment system that ensures adhesion of full-wrap labels and induction cap seals.

The technology is said to offer more uniform weight distribution, as the weight of each resin shot is controlled with a servo-controlled melt pump.
The pre-blow process allows a more consistent and uniform wall thickness by making it easier to separate plastic from the compression core. The blow process begins immediately after compressing the preform, leaving less chance of material sticking to the metal core rod.

Largely thanks to lower process temperatures the system economises on energy compared to other processes. As the machine’s conveyor features an air conditioner and dehumidifier, the bottles can be taken out hotter, reducing cycle time.

A leak detection is fully-integrated immediately after the bottle is blown, while the system uses infrared cameras to detect surface and internal contamination, like finish variations or metal particulates. Furthermore a plasma surface treatment system is installed as an alternative to flaming. Plasma treatments offer the same benefits of flaming, but cut down on environmental, health and safety risks.

Amcor’s current CBF machine is a 12-cavity unit that can create monolayer HDPE bottles 24-33 mm in size. That machine at Amcor’s Youngsville, North Carolina plant, is, according to Amcor, is a “game changer”, as they offer a higher-output, are more sustainable and produce higher-quality bottles than traditional injection blow moulding machines.

The company states that a 20-cavity unit is in production and should be available for commercial use by the end of the year. The 20-cavity machine will also have the ability to run HDPE, polystyrene, polyethylene, and PET. This would make it the only technology on the market that can use the four main resins used in packaging,

Neck-to-Neck
I am well aware that the Neck-to-Neck (N2N) technology, as well as the side-to-side is not new. But apparently the system is not widely known and never took off properly until recently.

The wheel/rotary blow moulders are the machine of choice for very high volumes of containers for markets such dairy and juices. Wheels are typically chosen over shuttles because of processing ease (and cost) due to the single parison technology and lower cost per container for high volume applications. This is especially true for co-extrusion and multilayer applications. The machine can be designed to handle a wide range of container sizes, but are typically committed to a narrow range of container variations after they are built. Because the containers are blown with a needle (instead of a blow pin), it is not unusually to blow containers in a neck-to-neck configuration to increase the production output. Wheels come in various configurations including indexing, continuous motion, vertical (like ferris wheels) and horizontal (like a merry-go-round). Some even now have the capability to produce calibrated neck containers. Most, however, rely on downstream trimming equipment to trim and finish the container.

Although the wheel/rotary blow moulders are known for their possibility to blow containers neck-to-neck it is the reciprocating screw/intermittent extrusion blow moulding system that got my attention.
The reciprocating screw/intermittent extrusion blow moulding system is the most popular and cost effective method to produce light weight dairy, juice and water containers. In this process the extruder feed screw reciprocates similar to an injection moulding machine. The moulds are stationary under the die-head and simple open and close but do not shuttle. As the screw moves forward, the parison is pushed out into the moulds for blowing. For light weight containers, cycle times can be very fast with some under 5 seconds.

In 2009 Uniloy, which had just introduced its Neck-to-Neck (N2N) UR Series reciprocating blow moulding machines, installed the first two Model UR90-16-N2N machine systems with Wimm-Bill-Dann Foods, a mayor dairy company in Russia, to produce white 100-mL HDPE liquid yogurt containers. This N2N machine produced two containers oriented neck-to-neck per cavity in a single cycle, producing over 20,000 of the 6.5 g containers per hour. This is a 30% material reduction in comparison to the previous 9 g.

The Uniloy reciprocating screw design gave primary advantages over wheel and shuttle blow moulding machines including lower energy costs, shorter dry cycle time, lower melt temperature and higher clamp force (90 tons). A wide range of head, clamp and extruder selections allows Uniloy Milacron to configure R2000 machines to desired production volumes and container specifications.

And now in the beginning of this year Uniloy Milacron announced that it sold another two reciprocating screw blow moulding machines to Wimm-Bill-Dann Foods in Russia. The new systems, delivered in March, will enable Wimm-Bill-Dann to add capacity to make 100-millileter containers as well as 200-ml.

In the same market segment, dairy products, juices and water, we see some interesting developments in manufacturing PET-bottles. That will be the topic of a next article.

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2 responses to “Manufacturing Single-Serve Bottles in HDPE

  1. Nice and interesting article, specially about the neck to neck technology. We are proud to have been Uniloy’s partner for the tandem blow neck to neck trimmer.

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