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1. Hot Melt Adhesives in Production

2. What are adhesives?
"Adhesives" are defined as materials that adhere simply through
pressing together the parts of the joint which requires bonding. At
room temperature, they demonstrate a lasting and permanent
bonding.
Hot melt adhesives are solvent-free adhesives. This means that
they are solid at temperatures below 180°F (82°C), become low
viscosity fluids above 180°F, and set rapidly upon cooling. Prior to
the development of hot melt adhesive technology, molten wax
was used for bonding. When molten wax was no longer an
effective solution, thermoplastic systems were introduced. Hot
melt technology stemmed from this evolution.

3. Hot Melt Technology Now
Today, hot melt adhesives are used in a variety of manufacturing
processes, including packaging, bookbinding and product assembly.
There are a number of hot melt adhesives in use, with the most common
being those used for hot melt pressure sensitive adhesive applications:
• Ethylene vinyl acetate (EVA) copolymers, compatible with paraffin, the
original hot melt • Styrene-isoprene-styrene (SIS) copolymers
• Styrene-butadiene-styrene (SBS) copolymers
• Ethylene ethyl acrylate copolymers (EEA)
• Polyurethane reactive (PUR) For the most part, additives like resins,
waxes, antioxidants, plasticizers and other materials are combined with
these polymers so that they can exhibit a full range of performance.

4. Hot Melt Technology Now
Some of these adhesives have been accepted in
many manufacturing industries, where they can be
applied in small bond points to eliminate use of
mechanical fasteners, like staples, screws, rivets,
clips, snaps, nails or stitching.

5. Uses & Properties
Hot melt adhesives are used primarily for
packaging, textiles, labels, tapes, and other
pressure sensitive applications, disposable
products, stamps, envelopes and product
assembly processes. Common household products
like diapers and disposable pads are made from
hot melt technology, along with a significant
amount of food packaging.

6. Hot Melt Processes
Hot melt production is a continuous process. In most
cases a compounder is used to produce a
homogenous melt. After plasticizing/masticating and
compounding the various rubbers, the resins (solid or
liquid) and softeners/oils are added downstream.
For larger quantities, the liquid can be fed at several
locations along the extruder, using multiple kneading
and homogenizing stages.

7. Feedrates and Ingredients
The typical throughput ranges are 100 - 1000 kg/hr,
(220 - 2200lb/hr).
Depending on the recipe and number of ingredients,
typical feed rates are:
• Elastomers: 30-50%
• Resins: 20 - 40%
• Softeners / Oils: 10 - 40%
• Fillers: 1 - 10%
• Color pigments: 0.1 - 3%, Stabilizers: 0.1 - 3%

8. High Accuracy Requirements
There are tough performance requirements on the
various types of hotmelts with regard to working
load and types of stress on the joints, temperature,
range, lifetime etc.
Typically there is a rather short residence time (as
little as 10 - 20 seconds) in the extruder's mixing
zone.To ensure constant high quality of the end
product, a continuous high feeding accuracy is
required for the additive feeders