July 18, 2016 - Assembly

Three Key Adhesive Application Methods for Filtration Media

In a recent blog, we looked at filtration media types and compatible adhesives. Now, let’s take a closer look at three adhesive application methods available:

#1: Spray/Melt Blowing Adhesive Application Method 

The spray/melt blowing adhesive application method is used on glass, polyester and nylon media. This method maintains the filter’s efficiency while lowering its pressure drop.

What Does This Method Do?

Spray/melt blowing creates a light layer of adhesive fibers that bond to the porous nonwoven media. The adhesive does not penetrate the filter media deeply. This means it does not affect the filter’s efficiency.

filtration media adhesive

What Types of Adhesives are Used?

The types of adhesives that are used in the spray/melt blowing application method are hot melt (polyester, HMPSA, EVA) and water-based adhesives.

In order to determine if the adhesive should be applied using a spray unit or melt blowing unit, consider the following:

If Using a Spray Unit:

  • Spraying/atomizing fluids require a higher pressure and smaller “nozzles” for the fluid to be dispersed the best. A lower viscosity product in this application method allows for less pressure to be used. At the same time, it does not damage machinery or clog up the atomizing orifices.
  • Application temperature is dependent on the product’s viscosity at that temperature. A viscosity of 600 cps or lower is ideal for an atomizing spray application.

If Using a Melt Blowing Unit:

  • The melt blowing process creates a randomized fiber layer. This means it is considered porous and perfect for filter media. (Please note: In order to not affect the filter’s efficiency, it’s important that the non-woven, randomized fiber layer has the same or similar relative filament size.) Since the adhesive “strings out” in creating the fiber layer, a higher viscosity adhesive is needed.
  • While the application temperature depends on the material being applied to, typically polyester and polyamide adhesives require more heat and pressure. This is due to their viscosities and melt points. (Please note: Some extruders may need to be used if the viscosity is higher, in order to “push” the adhesive through the melt blowing nozzles. Other, lower viscosity melt blowing adhesives may only need to be melted in melt tanks instead of extruders due to their appropriate viscosities.)

Typically, water-based, HMPSAs, EVAs and some polyolefin adhesives can be sprayed. Other, higher viscosity and higher application temperature adhesives may need to be melt blown.

#2: Gravure/Roll/Dot Lamination Adhesive Application Method

This type of adhesive application method is used for any filter media that is paper-like in nature.

What Does This Method Do?

This adhesive application method uses an exact pattern of microscopic “dots” of adhesive to bond a range of similar and dissimilar materials together. These materials include nonwovens, films, fabrics or composites. A rotating gravure roll is used to pick up and deposit the adhesive as the material rolls through the equipment.

What Types of Adhesives are Used?

Hot melt (polyester, polyamide, EVA) and water-based adhesives can be applied to filtration media using the gravure/roll/dot lamination method.

Benefits to using this type of application method include:

  • Consistent pattern application
  • Good control over amount of adhesive applied

However, it’s important to note that this application method has a tendency to reduce filtration efficiency with plugged pores, and it may be tough to changeover from one adhesive to another.

#3: Web Adhesive Lamination Adhesive Application Method 

This type of adhesive application method is used for media typically compatible with polyester, glass, nylon and certain PP/PET.

What Does This Method Do?

Web adhesive lamination is used to apply pre-melt blown polymer resins (polyesters, polyamides, polyurethanes, polyolefins).

What Types of Adhesives are Used?

Web adhesives are used to bond together two layers of filter media. These versatile adhesives are created using hot melts that are into a web-like, non-woven material that handles like fabric.

In this adhesive application method, the web adhesives come as a “roll”, which is then unwound and sandwiched between the two media layers. The sandwich is pulled through a flatbed laminator, which heats and applies pressure to the adhesive and media. This causes them to bond together.

The finished product is brought through cooling plates, wound and ready to be shipped to the customer.

Benefits to using this type of application method include:

  • Easy handling
  • Minimal equipment needs
  • Maintains filter’s efficiency

As a global leader in the adhesive market, Bostik will provide you the expertise about adhesives most compatible with your application, and the best application methods for your processes. Contact a Bostik representative to learn how adhesives can benefit your filtration manufacturing production.

Check out more content to learn about adhesives in filtration:

On Demand Webinar: Understanding Your Adhesive Needs In Filtration

Are You Paying Too Much for Your Filter Potting Compounds?

VIDEO: Improve Filter Manufacturing

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