Bildquelle: alle Angst+Pfister

Source: all Angst+Pfister

Introduction

Friday, 3 o’clock in the afternoon. A supplier of components for coffee machines receives a desperate call from his customer, a leading coffee machine manufacturer for the consumer market. The problem: a whole cargo of coffee machines will be immediately returned, as customs officers in China will not authorize it to enter the country. The reason: lack of the corresponding GB 4806.1 approval, as the US FDA one is no longer considered valid for the Chinese market. At about the same time, another important coffee machine manufacturer, dedicated to the professional market, faces a technical challenge: an O-Ring sealing the piston of his brewing unit breaks after only 10 thousand cycles. Friction, hot water and cleaning processes with chemicals are responsible for a considerably shorter lifetime than all other elements of the brewing unit, making cost intensive maintenance operations necessary.

The examples mentioned above illustrate the increasingly demanding requirements which have to be satisfied in various food and beverage industry applications, leading to specific and tailor-made sealing solutions based on ultra-high performance materials.

In food and beverage applications, aseptic processes play an outstanding role. However, hygiene is only one of the important requirements that can be fulfilled through pure materials and applying hygienic design principles. The sealing material must withstand processes such as Sterilization-in-Place (SIP) with hot steam, or Cleaning-in-Place (CIP) with cleaning media. Oftentimes, exceptional mechanical capabilities are essential, as seen in the brewing unit example.

Besides, more and more global customers require the industry-specific approvals of all major markets like Europe, China, South America or the US. In Europe alone, the regulatory framework is provided by the Regulation (EC) No 1935/2004 of the european Parliament and of the Council of 27 October 2004 on materials and articles intended to come into contact with food and repealing Directives 80/590/EEC and 89/109/EEC. Confronted in various markets by comparable regulations, sealing materials have to comply with them avoiding proliferation of numerous country-specific solutions, as seen in the GB approval example for China.

Finally, there is a growing concern across the industry about certain elastomers containing a higher proportion of Polycyclic Aromatic Hydrocarbons (PAHs), proven to be carcinogenic. PAHs form a group of organic compounds consisting of two or more fused aromatic rings. They are a natural component of mineral oil-based plasticizer oils and carbon blacks, and are therefore found in numerous elastomers. The PAH limit values are divided into three categories, with Category 1 having the most restrictive limits for materials intended to be in contact with foodstuffs or to be put in the mouth, as well as for materials used for toys with long-term skin contact (longer than 30 seconds).

Figure 1 shows a comparison between the PAHs content of two FKM compounds and the limit required for PAH Category 1.

Abb. 1: Vergleich zwischen Ultra Pure FKM und einem Standard-FKM. Das Ultra Pure FKM erfüllt aufgrund des extrem geringen PAK-Gehaltes die 
PAK-Kategorie 1, während das Standard-FKM die Grenzen des PAK-Gehalts überschreitet und somit nicht mit der PAK-Kategorie 1 konform ist.

Comparison between Angst+Pfister’s Pertec Ultra Pure FKM  and a standard FKM.  The ultra-pure FKM  easily complies with PAH Category 1 due to its extremely low PAH content, while the standard FKM exceeds the limits of PAH content and thus cannot be compliant with PAH Category 1.

Facing many of the same challenges as in the rest of the food & beverage industry, coffee machines provide a showcase for the type of requirements placed on manufacturers of sealing solutions. With increasing consumption in developed markets –according to a recent survey from the agency Reuters[1], almost two out of every three Americans 18 years old and above drink at least one cup of coffee a  day-, and quickly expanding new markets –according to CBS News[2] Starbucks recently announced that it will open 3.000 new shops in China over the next five years-, coffee machines will face increasingly demanding specifications that need to be met on a global scale.

The Pertec product range is Angst+Pfister’s answer to fulfill these requirements, and its success is the best proof of how the food & beverage industry can benefit from choosing the most appropriate partner and solutions for its sealing technology needs.

 

 

 [1] Prentice, Chris. “Americans are drinking a daily cup of coffee at the highest level in six years: survey”. Reuters. Health News, March 17, 2018

Sealing Applications for Coffee Machines

From the point of view of sealing technology, there are two different environments within a professional and/or large domestic coffee machine which influence the selection of the right sealing compound:

  1. Cold water cycle: water is pumped out from the water tank, passing through a flow-meter regulating the amount of it needed for the desired type of coffee. Water is then brought up to temperature by a heating device, thus starting the next phase.

Requirements: Excellent performance compounds with a high grade of purity, providing a good price-to-performance ratio, with all main food & beverage approvals required in the most important markets.

  1. Hot water cycle: water enters the brewing unit at a high pressure, passing through grounded coffee. Afterwards, the coffee spout guides brewed coffee into a coffee cup.

Requirements: Top performance compounds with good mechanical resistance, low friction coefficient & very good water & steam resistance. Approvals for food and beverage in the main markets are also a must.

[1] Prentice, Chris. “Americans are drinking a daily cup of coffee at the highest level in six years: survey”. Reuters. Health News, March 17, 2018

[2] Tracy, Ben. “China embraces coffee culture craze, thanks to millennials”. CBS News, June 6, 2018

Abb. 2: Kalt- und Heisswasserkreislauf in einer professionellen oder grossen Haushaltskaffemaschine.

Cold and hot water cycles within a professional or large domestic coffee machine. 

Cold Water Cycle – Most suitable Sealing Compounds

For the sealing elements within the cold water cycle, some manufacturers have traditionally selected EPDM, standard VMQ, basic NBR, or any combination of these for the different components of the coffee machine. While being good choices from a purely functional point of view, a standard EPDM achieves only a PAH Category 3 classification, a category covering materials not suitable for contact with foodstuffs and intended only for short term skin contact. Moreover, using different compounds leads to unnecessary complexity in terms of specifications and logistics.

 

Abbildung 3 PERTEC UP VMQ table

Comparison of VOC-value of Pertec UP VMQ and standard VMQ (HTV and LSR compounds).

Pertec UP VMQ is an ultra-pure silicone compound developed by Angst+Pfister with the specific requirements of food & beverage applications in mind. Its wide temperature range, covering from -60°C to +200°C, together with its good chemical resistance, makes it a perfect solution for these types of applications. It also covers a wide spectrum of approvals such as FDA, GB 4806.1, French Arrêté, BfR XV, EC1935/2004, 3A Sanitary etc. It easily meets the criteria for classification under PAH Category 1 –contact with foodstuffs- and has an extremely low VOC (Volatile Organic Compound) value, as shown in Figure 3.

Result: a single sealing compound meets all requirements, eliminates any possible health concerns, and avoids complexity for the customer derived from product/compound proliferation.

Cold Water Cycle application example: Sealing Compound for the Flow Sensor

Flow sensors are a critical part as they measure the quantity of water for a cup of coffee, which varies according to the type of coffee being prepared. The O-ring has to perfectly seal the two plastic parts in an open groove. The media is cold water with very low pressure.

The ultra pure VMQ solution works on three different levels:

  • Product Dimension: fulfilling approvals from the drinking water and food & beverage industries, including PAH Category 1.
  • Special Packaging: the O-Rings are specially packed in air filled bags to prevent deformation during transportation.
  • Added Services: micro talc layer preventing the O-Rings from sticking together and allowing them to slide properly through the assembly line, resulting in a considerably higher efficiency of the production process.

Hot Water Cycle – Most suitable Sealing Compounds

In such an environment, the materials selected for the sealing application must comply with food specifications such as BfR, FDA, EC 1935/2004, 3A standard sanitary, etc. They should have a high chemical and temperature resistance in order to retain their sealing functionality during and after exposure to CIP processes, to high temperature steam used for sterilization, and to the brewed coffee containing hydrocarbons or fatty acids.

CIP products usually contain aggressive, oxidizing and alkaline chemicals such as nitric acid, hydrogen peroxide, peracetic acid, sodium hydroxide and potassium hydroxide. The cleaning process itself is conducted at temperatures around 75-85°C. Traditionally, coffee machine manufacturers have selected silicone and EPDM compounds for the hot water cycles, but neither one of these compounds can provide optimal durability and stability under the CIP conditions.

In the case of silicone compounds, the siloxane backbone is prone to degradation when exposed to high temperature processes combined with usage of acid and/or alkaline substances, which would lead to the gasket being significantly damaged after several hot water cycles.

EPDM, on the other hand, could be a good solution considering its resistance to high temperatures and strong acid and/or alkaline media during the CIP process. However, EPDM might suffer degradation due to its affinity toward chemicals contained in brewed coffee, such as hydrocarbons and fatty acids, rendering it unsuitable for this application.

For this reason Angst+Pfister developed the Pertec CIP FKM 75.501-04 compound, an FKM peroxide grade that is able to endure the harsh conditions of the Cleaning in Place process (see Figure 4). It also offers an exceptional mechanical resistance while complying with all major food regulations worldwide.

Abb. 4: Beständigkeit von CIP FKM im Vergleich zum FKM eines Wettbewerbers unter Einwirkung verschiedener saurer und alkalischer Medien sowie von Sattdampf und deionisiertem Wasser unter den entsprechenden Bedingungen für 168 Stunden.

Overview of the resistance of Pertec CIP FKM in comparison to a competitor’s FKM upon exposure to various acid and alkaline media as well as to saturated steam and deionized water at the corresponding conditions for 168 hours.

Although the Sterilization-in-Place is not as relevant in the case of coffee machines as for other food & beverage applications, the compound is also a best-in-class solution in terms of its high resistance to hot water and steam, thanks to the latest Nano-Fluoro Resin technology present in the compound.

Hot Water Cycle application example: Sealing Compound for the Brewing Unit

 The brewing unit, where water and grounded coffee grains are blended together into a full-flavour espresso or a delicate café crème, is undoubtedly the most important component of the whole coffee machine.

The brewing unit presses hot water through a piston into the grounded coffee performing a vertical linear movement. During this operation, an O-Ring or a lip seal are needed to perfectly seal the piston. In addition to the chemical resistance challenges posed by the CIP process, during every cycle the sealing elements are submitted to friction from ground coffee residues, coming in contact with fatty acids from coffee beans.

A degraded or broken seal in the brewing unit would certainly lead to the coffee machine being unable to function altogether.

Compared to a regular silicone compound lasting 10 thousand cycles, the usage of CIP FKM in this application allows the useful life to be extended to 40 thousand cycles. This lifespan extension reduces the intervals between costly maintenance operations. Besides, its multiple approvals for food and beverage applications allow it to be used in coffee machines sold all over the world.

Abb. 5: Mikroemulsionstechnologie: Ein Nanopartikel aus PTFE-Latex ist mit einer FKM-Außenschicht ummantelt.

Micro-emulsion technology: a nano-particle of PTFE Latex is bound with an FKM outer.

Nano-PTFE: the secret behind good mechanical properties and high abrasion resistance

Through the technology of micro-emulsion a new class of peroxide curable Pertec FKM compounds was developed based upon nano-PTFE (see figure 5). Compared to other fillers such as PTFE powder, nano-PTFE ensures homogenous dispersion of PTFE and provides good mechanical properties. Compared to a coating process, it offers better abrasion resistance as well as high hardness and high elongation capabilities.

 

 

Depending on the application the concentration of the nano- PTFE may vary from 0% up to 40% weight percentage of total polymer content, with 30% nano-PTFE optimizing the balance between mechanical properties (Figure 6) and high abrasion resistance (Figure 7).

Abb. 6: Mechanische Eigenschaften von Verbindungen, die mit Nano-PTFE als Füllstoff in 
verschiedenen Konzentrationen hergestellt werden.

Mechanical properties of compounds produced with nano-PTFE as filler in various concentrations.

Summary

The food and beverage industry imposes increasingly challenging requirements for sealing solutions manufacturers, both in terms of performance well as food and beverage related regulations. Under these circumstances, traditional compounds do not always provide the best solution, potentially leading to high costs when they fail to meet these requirements.

Abb. 7: Abriebfestigkeit von Nano-PTFE-Füllstoff (30 %) im Vergleich zu Russ- und PTFE-Pulverfüllstoffen.

Abrasion resistance of nano-PTFE filler (30%) in comparison to carbon black and PTFE powder fillers.

It is therefore strongly suggested to use sealing elements from companies with proven competence to engineer and manufacture sealing solutions that can overcome all technical and meet the regulatory requirements. For this purpose the compound production and a high reliability of the whole manufacturing process (moulding, de-flashing, grinding, post curing and inspection) are crucial aspects.

Angst+Pfister uses its established engineering know-how to develop and produce ultra-high performance proprietary sealing compounds, aimed precisely at satisfying the high technical & regulatory requirements of the food & beverage industry.

Angst+Pfister’s elastomer range for technically challenging and high-performance demanding applications.

Angst+Pfister’s elastomer range for technically challenging and high-performance demanding applications.

The Pertec product range proves that it is possible to meet all requirements without making any compromises or shortcuts, as established in the example of coffee machines. Moreover, the case study clearly shows that this can be done while reducing costs by making production processes more efficient, increasing maintenance intervals and reducing complexity driven by the use of different compounds according to the desired performance and/or regulatory compliance.

 

 

 

PERTEC® is a brand of the Angst+Pfister Group

About the authors

Andres Messmacher

Head of Product Leadership
Angst+Pfister Group
Zürich, Schweiz

Fabio Falco

Development Engineer for Compounding
Head of Product Leadership
Angst+Pfister Group
Zürich, Schweiz

Erich Schmid

Chief Technology Officer
Angst+Pfister Group
Zürich, Schweiz