So that "closed" also means tight

System solution for sealing open top drum lids

So that "closed" also means tight

The cylindrically shaped lidded drums made of black plate, tinplate or steel or plastic really get production and consumption rolling in the truest sense of the word. As storage aids and transport containers for industry, they are the global standard for filling, storing and transporting many types of products. Most steel and plastic drums meet UN approvals for drop testing, pressure and stacking through the combination of sealing and closing mechanism for the drum lid. Depending on the intended use, a drum may also need to have UN hazardous materials approval, which requires drums to withstand high pressure and be leak-proof during drop tests. Henkel's Sonderhoff Fermapor K31 polyurethane foam seals provide the perfect seal against leakage and contamination. They are part of a complete system solution comprising sealing material, mixing and metering equipment, and process automation for fully automatic material application.

The lidded metal drum usually consists of a hull, bottom and lid. In the body there are reinforced beads, typical of this barrel, evenly spaced, so that it is easier to roll and gives stability to the barrel. It is now usually closed with a polyurethane foam sealed metal lid and clamping ring. Due to the wide range of internal coatings, most goods can be packed and transported in steel drums. They are mainly used for storage of solid, pasty or powdery materials. The filling volume ranges from 25 liters of the smaller metal containers called pails or hobbocks to 220 liters in lidded drums.

The cylindrical-bellied plastic drums, in typical blue with black lids, on the other hand, are often used as containers for the food, cosmetics or chemical industries and have a low dead weight without sacrificing stability, stability and safety. They are usually made of high-quality polyethylene plastic HDPE (high-density polyethylene), which is particularly dense, unbreakable and resistant. HDPE is also tasteless and odorless, making it excellent for food storage.

Fig. 1: Metal or plastic lidded drums with polyurethane foam lid seal and clamping ring for sealing.

Tailor-made sealing foams for maximum packaging safety

With its Sonderhoff brand, Henkel has many years of experience in the production of 2-component polyurethane foam gaskets for sealing metal and plastic lidded drums and offers the matching mixing and metering machines for material application using the Formed-In-Place-Foam-Gasket (FIPFG) technology.

The requirements for lidded drums made of black plate, tinplate, and steel are as varied as their contents. Sealing the drum lids with Sonderhoff's Fermapor K31 polyurethane sealing foam protects against leakage or contamination of packaged goods in conjunction with the entire container design.

Depending on the formulation, the seal usually has good adhesion to internally painted metal drum lids. For even better adhesion, especially on plastic lids, the lid contour can be pretreated with plasma or primer.

Provided that the container design is suitable for the transport of dangerous goods, special formulations of Fermapor K31 polyurethane foams also meet the tightness requirements of the UN dangerous goods approval. In any case, the drums must be leak-proof even in the event of drops, impacts or vibrations in accordance with UN approval (Fig. 2).

Fig. 2: Drums with UN hazardous goods approval must be leak-proof and withstand high pressure in accordance with the applicable drop tests.

Different polyurethane foam formulations are used for sealing the lids of metal drums (Fig. 3) for technical products, such as paints, coatings, construction materials and aggregates, or filled raw materials for foodstuffs.

The formulation of the lid seals for food drums has been tested for safe use in direct contact with liquid, alcoholic, fatty and dry foodstuffs in accordance with the European standard EU 10/2011 and the German LFGB (in accordance with Sections 30 and 31 (1) of the German Food and Feed Code).

Fig. 3: Metal drum with PU foam seal in lid

The lids of plastic drums (Fig. 4) with a filling volume of two liters or more for foodstuffs are seamlessly sealed with a special Sonderhoff Fermapor K31 polyurethane foam, which is FDA-compliant in accordance with Title 21 of the US Code of Federal Regulation ("US Code", 21 CFR § 174.5).

Fig. 4: Plastic drum with sealed lid and clamping ring

This polyurethane foam seal is generally suitable for use in direct contact with aqueous, acidic, alcoholic, fatty and dry food raw materials. This also applies to cold or hot filled or pasteurized milk and dairy products. The correct ratio of the contact area of the seal surface to the filling volume must be maintained.

The FDA-compliant foam gasket is also characterized by very good migration behavior of the gasket materials used in the formulation. The expert opinions of independent testing institutes certify that the values determined for total migration of the gasket materials are below the limit value of 10 mg/dm² specified in EU Regulation No. 10/2011. The odor and taste as well as the appearance and consistency of the food filled in plastic drums do not change. Henkel can adapt Sonderhoff sealing foams to the specific technical requirements of its customers and, for example, adjust reactivity, hardness, viscosity as well as color and other chemical and physical properties to customer specifications.

Mixing and dosing systems for precise and efficient metering processes

Henkel is a process expert for the sealing of drum lids and, with its FIPFG technology, offers economical and efficient solutions for the customized automation of manufacturing processes, especially for the high volumes and short cycle times that are common here.

The reference configuration shown in Fig. 5 is used for the fully automatic and contour-accurate application of 2-component sealing foams into the lid groove of metal or plastic drums.

This system consists of the Sonderhoff DM 502 mixing and dosing machine for processing two material components, a 3-axis linear robot, a refilling station, and a conveyor belt system for part feeding and unclocking. The highly dynamic LR-HD used ensures contour-accurate guidance of the MK 825 PRO precision mixing head over the lid contour.

Fig. 5: Mixing and metering system 502 with conveyor belt for part feed and cycle-out

The drum lids are fed to the dosing station under the 3-axis linear robot at the cycle rate specified for your production. At the centering station, the lid is positioned on the belt in such a way that the mixing head controlled by the linear robot can traverse the lid groove with contour accuracy and thereby apply the precisely metered discharge quantity into the groove.

Alternatively, the sealing foam can also be metered into the lid groove by rotating the lid in a device designed for this purpose. In this case, the discharge quantity is introduced into the lid groove via the mixing head as a function of the rotation speed.

In both application variants, the sealing foam is introduced into the lid groove with high metering and repeat accuracy. The coupling point of the foam seal closes seamlessly and is thus almost invisible. After foaming up several times the specific material volume, a flexible foam gasket of the desired foam hardness is produced, which cures at room temperature.

Compression behavior of foamed gaskets

The sealing function of the polyurethane foam gasket is achieved at a compression of approx. 30 to 60 % (Fig. 6.1 / 6.2)

Fig. 6.1: Groove cross-section: The uncompressed polyurethane foam in the groove (left) is compressed by the counterpart by approx. 50 % (right).

Fig. 6.2: Groove cross-section: The polyurethane foam in the groove is compressed by the counterpart by approx. 50 % (right).

The good compressibility of polyurethane foam due to its mixed cellularity allows any component tolerances of the drum lids to be compensated for during sealing.

When the drum lid is closed (Fig. 7 / 8), the elastic cell structure of the foam seal is compressed, and the drum lid sealed. Even with repeated opening, the foam seal always recovers almost completely and can be resealed.

Fig. 7: The polyurethane foam seal compresses in the groove of the metal lid when it is closed and seals.

Thanks to this very good recovery behavior of the mixed-cell polyurethane foam structure, there is always sufficient foam height to ensure that the polyurethane seal can still be compressed well after years without the sealing effect diminishing.

Fig. 8: The polyurethane foam seal in the plastic lid groove compresses and seals during closure.

Depending on the test conditions (according to DIN EN ISO 1856), the recovery behavior of the polyurethane foam seal is approx. > 95 % or < 5 % DVR (compression set).

Summary

 The leading manufacturers of drum lids have been relying on the wide range of properties of the material systems from the Sonderhoff portfolio for decades. In addition, the Formed-In-Place-Foam-Gasket (FIPFG) sealing technology offers the advantages of lower costs and more efficient material use compared to the sponge rubber gaskets commonly used in the past. The wide range of system configurations with different equipment options for semi-automatic or fully automatic production can be variably adapted by the user to his production conditions.

The customer gets a sealing solution perfectly tailored to his requirements with a high-precision metering machine that ensures contour robot-controlled, fully automatic material application. The user also has access to Henkel's many years of automation and process expertise.

In all system solutions from Henkel, the focus is on ensuring that the dispensing technology, material system and process automation are perfectly matched to one another - for highly reliable, process-stable material application, minimized maintenance times and consistently high dispensing quality.