By: George Benoit

➢ Return on Investment

CONGRATULATIONS!

You have worked diligently to develop new and improved formulations for the

hot melt adhesive industry, and in turn will continue to substantiate your

corporation as a leader in the industry.

Now your corporation needs to determine the best method to implement, in

order to present the materials to the market in a form that is not only user

friendly for the end user, but cost effective to produce.

A few key points to be considered when determining which equipment to use:

➢ Capital Investment

➢ Efficiency➢ Reliability

➢ Ability to process a broad

range of materials

➢ Flexibility to adapt to future

process requirements

Examples of some of the forms for producing Hot Melt Adhesives

• Block• Chiclet • Pillow

• Strand• Pastille • Underwater Pellets

HOT MELT ADHESIVES

UNDERWATER PELLETIZING APPLICATIONS

➢ EVA: Ethylene-vinyl acetate

➢ PP: Polypropylene

➢ PE: Polyethylene

➢ PA: Polyamide

➢ TPE: Thermoplastic Elastomers

➢ APAO: Amorphous Poly Alpha Olefin

➢ LMPP: Low Molecular weight & Low Modulus Polypropylene

➢ Metallocene

➢ Phenolic Resin

➢ Adhesive Grade TPU

➢ Polyester

➢ PSA: Pressure Sensitive Adhesive

(SIS): Styrene-Isoprene-Styrene

(SBS): Styrene-Butadiene-Styrene

Benefits of the Underwater Pelletizing Process

➢ Spherical free flowing adhesive pellets

➢ High degree of automation

➢ Low space requirements

➢ Moderate operating expenses

➢ Ability to process the broadest range of adhesives regarding

viscosity, percentage of fillers, and material bases.

➢ Flexibility to adapt to future process requirements

➢ Ability to package and ship product immediately

In this process, a molten polymer is extruded through the holes of a die

plate in order to form pellets. As the molten polymer flows from the die,

pellets are cut by the blades attached to the pelletizer cutter hub. This

takes place in the housing called the water box or cutting chamber.

Process water is flowing through the cutting chamber and across the die

face – thus the term “underwater” pelletizing. The purpose of the process

water is to transport the pellets to the dryer and to cool the pellets so they

solidify before entering the dryer.

Defining Components

of

The Underwater Pelletizing Process

DEFINITIONS

Process Water Conditioning:

The Tempered Water System (TWS) is the internal conveying system of the Gala underwater

pelletizing system. The Integrated Sieve (IS) Tank Design features a V-wire screen mounted

under the dryer water outlet to filter solids from the process water prior to recirculation to the

pelletizer. The TWS provides automated start-up and shut down, and is designed with the

appropriate safety guards and redundant safety interlocks.

Centrifugal Drying:

The Centrifugal Pellet Dryer features double walls filled with insulating material. Sound

pressure level of ≤ 80 dB(A) is possible. Large, wide doors and larger distances between

rotor screens and dryer walls provide easy access to the interior. The slurry of pellets and

water pass through a dewatering section before entering the centrifugal dryer. From here

the pellets and residual water flow into the rotor section of the dryer where the pellets will be

conveyed by centrifugal action and the residual moisture will be removed through the

screens and by counter current air flow. All Gala dryers are supplied with door timed

interlocks and local power disconnect for operator safety.

DEFINITIONS

DEFINITIONS

Pelletizer:

The Manually Adjustable Pelletizer (MAP) features a manual adjusting wheel to position the

blades against the die plate. This simple blade adjustment design provides visual blade

wear indication and maximum control of blade position. The unique design of the axial

advance system replaces the need for a bearing housing assembly. The MAP design

requires only one long life thrust bearing for accurate adjustments. The Gala Pelletizer is

designed with the appropriate safety guards and interlocks.

Waterbox Bypass:

The Waterbox Bypass Piping Assembly is incorporated in order to provide the ability to

service the pelletizer by routing the process water away from the cutting chamber without

having to stop circulation. This results in maintaining proper water flow and temperature for

the process and efficient start up. The valving for the Waterbox Bypass is automated and

interlocked for proper sequence of operation and safety.

DEFINITIONS

Powder Feeder:

The Powder Feeder is incorporated for products that require a “dusting” to the surface of the

pellet in order to reduce the effects of surface tack. The powder feeder allows for reliable

control of the flow and increased accuracy for the process.

DEFINITIONS

Process Control System:

The Process Control System is designed to Gala’s specifications and covers the entire range

of customer requirements, from the simplest systems to comprehensive control systems

including visualization. High quality components are used to achieve superior performance

and operating safety. Individual control systems are customized to the different pelletizing

systems and customer requirements.

DEFINITIONS

The Material Pump is incorporated in order to build pressure and provide stability for the process of

underwater pelletizing. Depending on the viscosity of the material and upstream equipment for delivery to the

melt pump, the design and selection for the melt pump will vary. The Melt Pump is designed with appropriate

safety guards and interlocks.

PoDV

The Polymer Diverter Valve (PoDV) is incorporated in order to provide the ability to start the production process

at full rate, therefore optimizing the conditions for underwater pelletizing of both low and high viscosity

materials. The PoDV also provides the ability to circulate material back to the mixing vessel or holding tank

after purging the die plate, therefore minimizing “waste and re-work” material. The Polymer Diverter Valve is

designed with the appropriate safety guards and interlocks.

PoDV

The Screen Changer is incorporated in order to provide fine filtration of the polymer and consists of a

hydraulically controlled piston(s) with a breaker plate. Replaceable screen packs are used for filtering. The

Screen Changer is designed with the appropriate safety guards and interlocks.

MC / HTS

PoDV

The Melt Cooler / Heat Transfer System is incorporated in order to lower the temperature of the HMA and

raise the viscosity to a point conducive for consistent underwater pelletizing. The system is designed to

lower the temperature of the HMA with a single pass through the melt cooler. The system is self-contained

and mounted on a permanent skid for ease of installation. The Heat Transfer System is designed with the

appropriate safety guards and interlocks.

MC / HTS

PELLET DIVERT

VALVE

PoDV

The purpose of the Pellet Divert Valve is to divert product (pellets) from the product outlet of the centrifugal

dryer during start-up, for product sampling or for filling containers. Operation of the Pellet Divert Valve can

be manual or pneumatically actuated depending on production rate of the system.

MC / HTS

PELLET DIVERT

VALVE

PoDV

The Tumbler can be applied in various applications and provides a less aggressive approach to processing

materials. The Tumbler has proven to be successful in both drying and coating applications for pellets,

and performs exceptionally well with brittle and tacky products.

MC / HTS

PELLET DIVERT

VALVE

PoDV

The Multi-port Valve (Rotational Valve) can be adapted to many applications. Whether the application

consists of a slurry of pellets and water, tacky pellets, or standard pellets, the Rotational Valve performs

exceptionally well for distribution of the pellets to multiple packaging stations and/or downstream

equipment.

MC / HTS

PELLET DIVERT

VALVE

PoDV

The Bagging System can be implemented for both PSA (Pressure Sensitive Adhesive) and/or HMA (Hot

Melt Adhesive) applications. The cooling of the pellets in the process, in conjunction with the use of a

specially formulated film for the bagging of the PSA, allows this product to be packaged immediately and

shipped to the end user. The film is formulated to dissolve at a lower temperature than the melting

temperature of the PSA and is compatible with the PSA, therefore becoming part of the formulation.

MC / HTS

DEWATERING

SECTION

PoDV

Brittle product applications may require the Centrifugal Dryer to be taken offline (or not incorporated) as

this method of drying may be too aggressive for the pellets. A Dewatering Section is incorporated to the

inlet of the Tumbler to separate the pellets from the water. Once entering the Tumbler the pellets are

introduced to a gentler form of drying which incorporates a series of blowers as well as a tube heater for

final drying of the pellets.

MC / HTS

DEWATERING

SECTION

PoDV

This example depicts an application with the Dewatering Section incorporated to the inlet of the Tumbler to

separate the pellets from the water. In this scenario, a Multi-Port Valve (Rotational Valve) has been

incorporated at the outlet of the Tumbler for distribution of the pellets to multiple packaging stations.

MC / HTS

DEWATERING

SECTION

PoDV

This example depicts an application with the Dewatering Section incorporated to the inlet of the Tumbler to

separate the pellets from the water. In this scenario, a Multi-Port Valve (Rotational Valve) has been

incorporated at the outlet of the Tumbler for distribution of the pellets to multiple bagging stations.

PoDV

A Twin Screw Extruder can be used in place of a vessel upstream of the Underwater Pelletizing Process.

The Twin Screw Extruder allows for better control of the formulation and minimizes the time span the

material is subjected to heat, which in turn results in a better product.

MC / HTS

PoDV

A Melt Cooler / Heat Transfer System can be incorporated with the Twin Screw application should

additional cooling of the material be required. The Underwater Pelletizing Process can be adapted

according to the requirements of the application in the same manner as the vessel application.

Ideal for slow crystallizing polymers

The PCS can be sized to fit any material rate and required residence time.

Improved physical properties

For some materials, pellet hardness can be increased and pellet tack can be decreased due to the

additional time in the process water.

Great for product development

Residence time is easily adjusted for the various running conditions that may be required for product

development.

Excellent for cooling pellets

For materials that retain heat, additional residence time can be used to cool the pellets prior to

packaging.

PELLET CONDITIONING SYSTEM

OUTLOOK

➢ Inline Color Injection

Development:

This system will provide the ability to inject color to the polymer

while in production, and eliminate the issues of having to do so

within the vessel. Resulting in less down time for clean up and

rework of material, which equates to more production of material.

The process of pelletizing hot melt adhesives under water in order to produce

pellets in the Gala FormTM began in the early 1980’s. Since this time, the

process has continued to evolve and adapt to the advancements and continued

development of formulations within the industry. Gala HMA Pelletizing Systems

are capable of processing a variety of hot melt adhesives ranging from EVA and

Metallocene based materials, PA, APAO, APP, PP, LMPP, PE, TPE, Phenolic

Resin, adhesive grade TPU, and PSA. Gala HMA systems have the ability to

pelletize brittle, soft, and high tack materials as well as materials with

viscosities as low as 400 cps.

The versatility of the underwater pelletizing process for Hot Melt Adhesives is

unique as the basic design of the system can be adapted from the simplest of

applications and formulations, to the more complex, and yet the basic principle

of underwater pelletizing remains the same and is reliable. Hence, allowing

the process the ability to pelletize a broad range of materials, maintain flexibility

to adapt to future process requirements, and as a result be efficient; therefore

providing a great return on investment.

SUMMARY

QUESTIONS

Thank Youfor

Your Time, Interest, and Attention