Auto additive container speeds past molding challenges

Tetrosyl (Rochdale, UK), the largest manufacturer and supplier of car care products in Europe, introduced a completely new product in a completely new container last September.

The custom blow molded high-density polyethylene container for Carlube AdBlue created by RPC Design (Rushden, UK) and produced by RPC Promens Industrial Plenmeller (Haltwhistle, UK) hurdled several speed bumps to successful commercialization. 

Carlube Adblue back side recessFor starters, the 3.5L pack features a special recess in the back to accommodate a lengthy flexible spout. The spout enables customers to dispense the AdBlue by providing easy access to the many differently-located vehicle filler caps. This technically-challenging requirement was achieved by increasing the capacity and footprint of the container and at the same time realigning the spout within the footprint.

Another benefit of this solution is that it leaves the front of the container completely available for labeling in order to maximize the on-shelf brand presence. User-convenience is further enhanced by the large handle and wide base for controlled pouring.

By way of explanation for readers in North America, AdBlue is the tradename for a urea solution that needs to be added to diesel engines with SCR (Selective Catalytic Reduction) systems to reduce nitrogen oxide emissions.

“Adblue is a liquid that is injected into the exhaust gasses from diesel engines,” explains RPC Design manager Brian Lodge. “It reacts with the gasses and removes nitrous oxide particles. All new diesel cars in Europe since September 2015 have a separate Adblue tank. This can be located in many different places on the car including under the bonnet (like an extra screen wash), next to the diesel filler cap or in the boot, depending on the car manufacturer. Any bottle design must be capable of reaching into all of these possibilities which is why there is the long flexible spout on the Tetrosyl bottle.”

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The new Carlube 3.5-L container is the result of a thorough study of the consumer market by Tetrosyl. The auto products giant concluded that this was the optimum size for the additive top-up market, combining the right amount of liquid with an easy-to-handle container.

The particular volume was chosen for a couple reasons. “Firstly, there is a need for the Adblue to be used all in one go and not stored after opening,” Lodge says. “This is because when exposed to air, the urea in the liquid can crystallize. If this happens it may not fully dissolve and can clog the injection device. This means we needed a smaller container to ensure that it could be drained all in one go; the Adblue tanks on cars can be a small as 7L.

“However, we needed a pack big enough to recess the tube into its side (to enable efficient and secure distribution). The minimum we could accommodate was the 3.5-L size.”

Next: Polymer selection, biggest challenge


Did the nature of the product affect the choice of polymers?

Adblue is a pretty inert substance, containing mainly urea and water therefore it doesn’t need any high barrier materials,” responds Lodge. “The bottle and spout are both made of HDPE as it is cost effective and provides all the strength and features required by both components.”

Carlube Adblue with spout

Both the bottle and spout are made by extrusion blow molding.

Regarding the container labels, Lodge informs PlasticsToday that rather than an in-mold label, the labels are a standard, clear polypropylene pressure-sensitive type applied after filling.

“That’s because the back label is used to hold the spout in place during distribution and this would not have been possible if we had used in-mold labels,” Lodge points out.


The biggest challenge

It’s easy for Lodge to identify the project’s biggest hurdle. “That was in designing the pack was to accommodate the spout in such a small footprint,” he says. “The resulting shape pushed the blow molding process to a great extent because of the ‘tortured’ nature of the recessed back surface of the bottle. This was not helped by the fact that only one side of the pack had this feature and the front was kept ‘clean’ to allow for the branding and graphics.

“The recess came almost to the part line of the molding which meant there was very little room to inflate the parison and form a bottle in the normal way.”

And there was more to that aspect as well.

“The recess came close to the container’s edges, so particular care was needed in creating a shape where the material could be blown into without forming very thin sections,” Lodge continues. “With both very thick and very thin areas on the same bottle we also had a problem with temperature differences and therefore differential cooling rates and shrinkage.

“To cap it all, we needed to add undercuts in the molding to ensure the spout was clipped securely in place.”

After all the research, development and effort, the container was proven a winner at the finish line.

“The new pack has been extremely well-received in the market,” says Shazad Shah, Tetrosyl’s Product Manager - Lubricants & Winter. “We have been delighted with RPC’s contribution to the project, in particular their responsiveness to our requirements.”

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