4 Advice to Choose a hot melt adhesive pellets

Selecting the right nozzles for your hot melt equipment can have a big impact on achieving throughput and performance targets with hot melt adhesive systems in end-of-line packaging operations. In order to make the right choice, there are three main factors to consider and evaluate:      

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· Understand Hot Melt Material Properties

· Know What Makes Your Application Unique

· Identify Maintenance Program & Goals

Once hot melt adhesive has passed through the heating process, the molten adhesive is transferred to the applicator or 'gun' for dispensing. Located at the very end of the gun, hot melt nozzles ultimately control the volume, velocity and direction of the dispensed adhesive.

These nozzles are interchangeable and are manufactured in multiple sizes and designs for a variety of dispense applications. Most nozzles fit into the following categories:

· Bead ' provide a single continuous bead or patterns

· Spray ' dispense in patterns at various widths and diameters

· Multi-line ' deliver multiple beads and patterns from a single nozzle

As part of a hot melt adhesive system, hot melt nozzles play a significant role in helping avoid waste and improve efficiency. When determining the effective hot melt nozzle diameter, a common misperception is that bigger is better to avoid downtime from nozzle plugs and keep the production line moving. While this approach may provide a short-term gain, it is important to understand that orifice size does not directly correlate to the amount of glue dispensed.

The limitations of the hot melt equipment should never dictate hot melt nozzle specification but unfortunately it does. It is common for manufacturers and maintenance managers to view hot melt nozzles as a consumable. However, the nozzles directly affect the performance/pump life of some hot melt systems.

With hundreds of hot melt adhesives available, the first step in selecting the right hot melt nozzle for optimum performance is to understand the characteristics of the hot melt adhesive material itself. Even within the same manufacturer product line, hot melt adhesive properties vary. For example, the viscosity of an EVA hot melt adhesive may be centipoise @ 350 degrees where a metallocene hot melt may have a thinner 700-900 centipoise at the same temperature.

The performance of the hot melt adhesive will have an impact on the performance of the hot melt adhesive system. This will be most noticeable at the point of dispense ' the hot melt nozzles. A best practice would be to involve your material supplier when optimizing hot melt equipment and specifying nozzles.

It is common to see an application where multi-orifice nozzles have been avoided because of low performance, carton pop-opens after leaving the manufacturing facility, and concerns for potential downtime issues.

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Another common mistake is when multi-orifice and single-orifice nozzles have been unnecessarily oversized to avoid nozzle plugs, rather than because either is the right nozzle for the application. Regardless of when this occurs (when setting up the line or implemented over time), it is always best to specify nozzles for the application rather than limitations of the hot melt system and equipment dictating nozzle selection.  

Regardless of the nozzle selection, one constant to maintain throughput and uptime is the need to clean and maintain the nozzle. Adhesive char is a common problem for end-of-line packaging systems and is the biggest foe for hot melt nozzle performance.

It is not uncommon for maintenance to extend the nozzle life or reuse nozzles by using hole pricks or small drill bits to keep hot melt nozzles open. While this may be a short-term solution to keep adhesive flowing, this approach will often increase the nozzle orifice size and lead to higher adhesive costs. Identifying and confirming maintenance  parameters with equipment suppliers will help maintain optimum performance without increasing material or spare parts costs.

Unwanted downtime and the issues that come with it can be avoided. Even in manufacturing environments with poor air quality and higher probability of contaminants entering into the hot melt adhesive, selecting hot melt equipment and nozzles that provide the highest amount of filtration can reduce downtime incidents by preventing contaminants from clogging nozzles. Some systems and nozzles are engineered to provide 'zero plugs'.

When possible, ask equipment manufacturers for proof of these claims and see if a demo program is available. The ability to see the equipment performing in the actual environment will help validate how their technology can improve issues with unplanned downtime related to maintenance issues.

Ultimately, correct nozzle selection has a direct influence on material management, operating expense and operator safety. Make sure to have a detailed understanding of hot melt adhesive materials, the unique demands of the application and the maintenance requirements to specify the right hot melt nozzles that will have the greatest impact on improving performance and production efficiency.  

1. How do I find the perfect adhesive for my edgebanding machine?

The right adhesive for each edgebanding machine depends on the manufacturer's specifications, and on the machine's feed speed. For example, glue cartridges can be used on machines with cartridge systems, such as Holz-Her machines. Other edgebanding machines require glue pellets. Choosing the right pellets depends on the machine's feed speed.

2. What does filled / unfilled mean?

With EVA HOTMELT ADHESIVE the customer can choose between filled and unfilled adhesives. Filled glues, in addition to the pure adhesive resins, contain fillers such as chalk which can influence the processing characteristics, e.g. by preventing stringing at low feed speeds. Unfilled hotmelt adhesives are comparatively lighter, as they consist of pure resin. They can be applied more thinly, and produce a thinner joint when optimally configured. You need a certain feed speed, however, to apply unfilled EVA adhesive.

Special tip:Our EVA hotmelt adhesive REDOCOL Kantomelt lightly filled offers a good alternative. Compared to unfilled hotmelt adhesive, the all-rounder is much easier to process and therefore particularly suitable for older and slow-running machines. There is no unwanted stringing or smearing of the adhesive. The hotmelt is further characterised by a low consumption and a thinner glue joint as well as good heat and cold resistance.

3. Granules, cartridge, block? What is the difference?

Depending on the manufacturer and machine type, the hotmelt adhesive is processed in different container forms. Most machines require granules which are poured into the gluepot. With other machines, the hotmelt adhesive is supplied as a cartridge or, in the case of PUR adhesives, as a 2 kg block.

4. Which adhesive do I use with feed speeds of 10 m/min and over?

Depending on the feed speed of the machine, different hotmelt adhesives must be used. To help you quickly find the right adhesive for your machine, we recommend using the faceted search function on our product pages. Here you can filter by brand, product, fillers, colour group, feed speed or even BAZ-capability. Simply tick the box that says 10 m/min and you will receive a list of all adhesives that are suitable for this feed speed.

7. What is the ideal processing temperature for my EVA adhesive?

With stationary edgebanding machines and machining centres, the ideal processing temperature for EVA hotmelt adhesives is 190 -210 °C. For mobile edge processing, the temperature is a lot lower, at 120-150 °C.

8. Which adhesive do I use if the bond needs to be extremely watertight?

If a joint needs to be particularly heat-resistant or waterproof, we recommend you to use PUR HOTMELT ADHESIVE. We provide PUR hotmelt from various manufacturers and for all application systems. Products from the REDOCOL family are of high quality and particularly economical. Before switching to PUR, however, you should make sure that your edgebanding machine has a Teflon-coated gluepot. Edgebanding machines with a cartridge feed are generally suitable for processing PUR hotmelt adhesives. At 100-150 °C, the ideal processing temperature for PUR hotmelt adhesives is well below that applicable to EVA hotmelt adhesives. It is also important to ensure gluepots and machines are cleaned after using PUR hotmelt adhesives. This involves always cleaning the edgebanding machine - unless it is due to be used the next day - with a corresponding PUR cleaning agent after using PUR hotmelt (e.g. REDOCOL PUR CLEANER).

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