Water Based Polyurethane (PUD) Shoe Glue

02 Ekim 2018


İbrahim Kecin

Chemist, M. Sc.
General Manager
PURIN Polyurethane

 

 

Ayşenur Dede
R&D Manager
PURIN Polyurethane

 

The very first binder (adhesive) was the tree alburnum/extracts obtained from natural sources and was used to make clay vessels.
After natural adhesives, the first synthetic adhesive came to exist in 1942 by Dr. Harry Coover’s discovery of cyanoacrylate.
Different adhesive systems followed over time.

The adhesives used today can be grouped as follows;
•Solvent-Based Adhesives
•Solvent-Free, Two-Component Adhesives
•Solvent-Free, One-Component Adhesives
•Solvent-Free, One-Component, Hot Melt Adhesives
•Water-Based Adhesives

When we look through the adhesive usage specifically in shoe sector, we see that solvent-based adhesives are in the forefront.
They are obtained by dissolving of polymeric materials such as polychloroprene, polyurethane and styrene copolymer in suitable
solvents. These products provide adhesion by removal of the solvent they contain.

If we take the example of bonding the shoeupper to the sole, binder applied separately to the shoe-upper and the sole. Then it is
dried at 140oC-180oC through an oven. The shoeupper and the sole, out from the oven, are adhered and pressed immediately
one another before the binder get cold. After that the adhesive, which cools down, sticks strongly.

When we look over this process technically, a kind of solvent which has two different vaporization paces is used to provide the
removal of solvent gradually as well as in the all coating and binding systems. Further more, these sticking applications are
performed by human power. Therefore, there is always a risk in the environment no matter how much investment is made for
workers’ health.

As PURİN Polyurethane, by the year 2018 we have started producing Turkey Water Based Polyurethane (PUD). We add a new
one to the PUD product groups day by day and increase our production volume in this area. Since we have considered PUD
technology as the future of polyurethane, we started our R&D work on this area long ago and started to produce domestically
with the investments in this area.

To explain PUD production simply;
The biggest obstacle in synthesis in polyurethane production is the water substance in raw mate-rials. So that, in moisture levels
over 300-400 ppm the synthesis cannot go on and it is necessary to remove the moisture from the environment with a suitable
drying agent. Otherwise, because of the reaction of isocyanates with water, molecule extension process of polymer cannot go on
and it is over. We can interpret that molecular weight of polymer directly as the product perfor-mance. Therefore; if we do not
extent the molecule, the product will be waste.

On the other hand, when we synthesize the product in a convenient environment, the exposure with water in application area is
another problem. Swellings will occur in the product because of the CO2 gas as the result of the exposure of prepolymer based
products with water and the product will end up with low performance. Nonreactive polyurethane products, on the other hand,
are coagulated after the exposure of water. PUD technology answers the question of how a synthesis is made in water, whereas
the water has such a negative effect on polyurethane synthesis and afterwards.

Products can be synthesized in 5 different stages with PUD technology;
Prepolymer Synthesis Stage: At this stage, prepolymer synthesis is carried out at proper stoichiometric ratios with polyol,
isocyanate, chain extender and hydrophilic monomer and cosolvent (e.g. acetone). Of course, the raw materials to be used
depend entirely on the application area, desired properties and performance. For example, when there is a need for hydrolyses
resistance, that is, nondegradation in aqueous areas is needed, polyether or polycarbonate-based polyols must be used instead
of polyester based polyols. Higher molecular weight polyols and long chain isocyanates must be used where high elasticity is
desired.

Neutralization Stage: Hydrophilic monomer used in prepolymer stage is the most important raw material in PUD technology. This
monomer provides the coherence of water with polyurethane chain. However, this monomer has an acidic structure and won’t
work directly by using in the synthesis. To activate this monomer, it should be neutralized with an appropriate base.

Dispersion Stage: Polyurethane chain could be dispersed in water after the neutralization. The product is changed into
watersoluble prepolymer form by adding water to the prepolymer under the mixer. After this critical stage, synthesis will proceed
in aqueous area.

Chain Extension Stage: At this stage, molecular weight extension is carried out to the polyurethane prepolymer, which is in
water, with diamine compounds. After achieving the desired molecular weight, the product is ready however there is a cosolvent
in the system which is needed to be taken out.

Solvent Recovery Stage: As the last step; cosolvent (acetone) in the completed product is absorbed out from the product by
vacuuming and heating. The end product is formed in this way. Thus, water based polyurethane resin synthesis is carried out by
PUD technology. Suitable raw material choice for application and performance is made with our experiences and technical
research before resin synthesis. We determine our optimum production way with the product analysis afterwards.

After the PUD resin synthesis conducting in control of Synthesis R&D department, Application R&D department do studies for
sectorial applications by making the required modifications on obtained resin.

Using PUD binder,
•Provides odor-free, clean and healthy working environment,
•Provides higher adhesion performance,
•Provides working easily with low viscosity,
•Provides minimization in the energy cost,
•Reduces the working stages,
•Increases production pace.

As PURİN, we will provide you a better service on PUD product groups than the sector like in all of our product groups;
•Developing technical projects and providing the most suitable product,
•Providing technical support by leading expert R&D experienced team on every processes (e.g. product choosing, application
and afterwards),
•Fast supply to entire Turkey and regional countries from our factory in Kocaeli,
•Providing the cost advantage with reasonable price as a local PUD producer.

Binders, which acquired with business development for the shoe sector, increase your production pace and provide minimization
in your working processes.