Sustainable Freshness with a Flick of the Wrist

A splash of lemon juice freshens up any salad and adds delicious flavor to many dishes. Lékué, a Spanish consumer goods manufacturer, makes it easy to add lemon exactly where you want it with its unique Lemon Press 1 silicone juicer. Their product allows you to juice lemons, oranges or limes and store them without leaving the cut surface exposed – a feat made possible by flexible yet durable silicone.

We were at the K 2022 International Trade Fair for Plastics and Rubber, October 19 – 26, 2022, where, in collaboration with our partners Nexus Elastomer Systems and ENGEL AUSTRIA, we produced this lemon juicer live at our tradeshow booth – using resource-efficient silicone, a newly developed mold and an automated injection-molding process.

Conserving Resources with Biomethanol-Based Silicones

As part of a live demonstration at K 2022, we presented the lemon juicer as the first-ever example of a food-grade silicone product made from plant-based methanol, i.e., methanol that has not been derived from fossil resources. To create these eco silicones, we determine the relative mass of fossil-based raw materials and additives in the product formulation and offset this with corresponding amounts of biobased methanol from sustainable sources. The products are certified to the REDcert² standard, ensuring traceability of renewable raw materials throughout our entire manufacturing process – from the production of important precursors up to and including solid silicone rubber compounded according to custom specifications. Environmentally friendly and produced using resource-efficient methods, these materials serve our aim of helping our customers meet their sustainable development goals.

Another unique development is fully automated, solid silicone rubber processing (HTV: high-temperature-vulcanizing). Working with our partners, we presented a stable, continuous, automated injection molding process.

Tough Yet Delicate

The strengths of solid silicone rubber products lie in their excellent mechanical and thermal properties, even in highly intricate components. The very thin external walls of the lemon juicer – no more than a mere 0.8 mm thick – are one example of this. The juicer has to withstand a fair bit: to juice lemons, users squeeze it firmly over and over, then store it at low temperatures in the refrigerator and clean it at high temperatures in the dishwasher, where it comes into contact with detergent liquor. And, of course, it has to be food safe. Solid silicone rubber is perfect for all of that. Available in a variety of formats for different customer applications, these compounds are ready-to-use materials with property profiles that can be tailored to the application at hand. The compound used at the tradeshow for the lemon juicer is SILMIX^® eco R plus TS 40002. The SILMIX^® brand includes customized, ready-to-use silicone rubber blends that we develop, compound and produce for you.

HTV Injection Molding in Minutes

We used the ENGEL flexSeal 300 hydraulic injection-molding machine with 3000 kN clamping force from ENGEL AUSTRIA GmbH to mold the material at our booth. Its horizontal machine concept with a reciprocating screw injection unit enabled exceptionally precise production in the small to medium shot volumes required. The RotoFeeder^® rotary conveyor, likewise from ENGEL AUSTRIA, fed the SILMIX^® eco R plus TS 40002 into the injection molding process. Its rotating hopper with counter-rotating screw transported the solid silicone continuously at a constant pressure and free from bubbles, thereby ensuring a very high level of process security – a huge advantage over the stuffers often used in batch feed processes up to now. The RotoFeeder^® also enables efficient cycle times (of roughly ninety seconds in this case) even with HTV materials.

Efficiency Starts with the Mold Technology

The actual lemon juicer was formed in the injection mold, however. Nexus Elastomer Systems had applied its extensive expertise to developing and constructing a horizontal, two-cavity slider mold. The material was injected directly into the mold cavities through a temperature-controlled cold runner and the Nexus Flowset needle valve system. One particular challenge here was to design the mold in a way that would keep bubbles from forming during filling and completely prevent any leakage of the low-viscosity HTV material, which flows through the mold under high pressure. A filling simulation run by the Sigmasoft company provided a detailed demonstration of how the material behaves in the mold, thereby supporting development in advance. The simulation was also available for viewing at our tradeshow booth.

Despite the complex component geometry, Nexus made it possible to demold components in a fully automated process. Following injection molding, these components required post-curing, as is typical for solid silicone rubber products intended for applications involving food contact.