Lamination Polyurethanes for Technical Textiles

Lamination processes, one of the most important applications in the textile sector, represent the most critical quality factor of the final product. For this quality, superior adhesive strength and wash fastness are the two priority parameters desired in lamination operations. As PURİN Poliüretan, we would like to introduce two of our products used in lamination processes in the textile sector with this article. One of these products is a solvent-based reactive polyurethane adhesive, while the other is our water-based adhesive manufactured using PUD (Water-Based Polyurethane Dispersion) technology.

Solvent-Based Reactive Polyurethane Adhesive Lamination

When examining the types of lamination applications in the textile sector, we encounter the following applications: 1. Flame Lamination 2. PVA Lamination 3. Latex Lamination 4. Hot Melt Lamination 5. Adhesive Lamination The first three of these applications do not provide sufficient product quality in terms of performance. Especially with PVA and Latex type applications, products such as disposable slippers are manufactured. Both the adhesive strength and wash fastness of these products are not very good. For this reason, they are preferred in disposable products from a cost perspective. Adhesive lamination and Hot Melt Lamination have the same structure in terms of polymer composition; both are reactive polyurethanes. The difference between them is that Hot Melt products do not contain solvent, so they exist in solid form under normal conditions. The lamination process is carried out by melting at temperatures such as 110-160°C. The adhesive lamination product is also a reactive polyurethane, but due to the solvent it contains, it exists in liquid form under normal conditions, and the lamination process is carried out without any heating operation. Therefore, since Hot Melt and adhesive lamination products have the same structure (both are reactive polyurethane adhesives), the following explanations apply to both.

The structure of reactive polyurethane adhesives is shown simply in the figure.

The reactive groups in these structures react with moisture in the air to complete the polymer structure, which indicates the product dries. The instantaneous tack/adhesion in Hot Melt products is not due to the product drying but due to its transition to solid form by nature of its structure. The product, which is in molten state due to temperature, cools toward environmental conditions when temperature is not applied, which causes the product to transition from liquid form to solid form. In Hot Melt adhesives, solvent-based adhesives react with moisture depending on ambient temperature within a certain period. The fundamental difference during application is their initial tack properties. Hot Melt adhesives achieve this through physical form change as mentioned above, while in solvent-based products we provide this property through high molecular weight due to formulation. Reactive adhesives bond to textiles in two ways. These bonds are covalent bonds and hydrogen bonds. Actually, textile is a structure with -OH functions, and this structure reacts with the product groups we call reactive polyurethane. While covalent bonds form through the bonding of OH groups on the textile with NCO groups on polyurethane, hydrogen bonds also form between the OH groups in the textile and the polyurethane bond. You can see this situation schematically below:

The application of our solvent-based polyurethane reactive adhesive can be done both with the cylinder method where PVA/Latex adhesives are applied and on Hot Melt machinery lines. Therefore, it does not create a serious investment cost for application.

Since our product is a cold-applied product, there is no need to even turn on the heating systems. In this way, the application energy cost is equivalent only to the motor energy spent for the machinery operation.

The consumption of our product is 10-15g/m². With the use of product in these amounts, superior adhesive performance and wash fastness are achieved. The wash fastness of laminated fabric obtained with our product exceeds 30-50 washes depending on the type of fabric and has superior adhesive performance. During the lamination process, since our product contains solvent, a system to remove this solvent from the environment is necessary. The only investment required to work with this product is this. The products to which application is made must be stocked for 2-3 days, as in Hot Melt lamination (since it is structurally the same product), and the reaction with moisture in the air must be completed. Or storing in hot rooms (70-80°C) for 12-16 hours, which is common in many lamination facilities, will be sufficient for shipment. When examining the summary table above for lamination processes, we see that the best performance is obtained from reactive adhesives. By creating a simple system to remove the solvent from our product's working environment, we can say that it provides a very significant cost advantage compared to the Hot Melt lamination method. We can evaluate these costs in three parts: 1) There will be no Hot Melt lamination machinery investment (EUR 300,000-400,000), lamination can be done with any type of cylinder. 2) Your application energy costs are eliminated. Instead of temperatures like 110-160°C for adhesive, application can be done at room temperature. 3) Your product cost is lower. Even if you have made a Hot Melt machinery investment, the reduction in your adhesive costs due to continuous adhesive purchases will provide you with a cost advantage. When you test that product quality is the same, reducing these costs will allow you to offer more competitive prices to the sector or increase your profit margin. When compared with Hot Melt adhesives, we provide a significant advantage of approximately EUR 1/kg. In conclusion, the fact that our product contains solvent may seem like a disadvantage. However, with a small modification in your facility, the removal of solvent will provide you with a very significant cost advantage for the same performance.

Water-Based Polyurethane Adhesive Lamination

Our water-based polyurethane adhesive product is a special product manufactured using PUD technology. It has superior properties that cannot be compared with water-based latex and PVA adhesives.

Some of these superior properties are as follows:

• Very high adhesive performance, • High temperature resistance, • High wash fastness. As PURİN Poliüretan, the application of this product group manufactured with PUD technology differs slightly from the products mentioned above. In fact, even the final product groups are different. Our product is in the form of polyurethane resin dissolved in water. Therefore, for optimum adhesive performance from the product, it must be applied using the following steps: • Water-based polyurethane adhesive is applied in a specific amount to the relevant surface (textile or other materials) by spray, cylinder or knife (doctor blade) method. • The surface to which adhesive is applied is passed through an oven to remove the water in the adhesive and expose the polyurethane resin dissolved in water. • The resulting polyurethane resin will be in a soft and adhesive form due to temperature. The second material to be laminated is applied with the help of a cylinder. • The materials laminated to each other are then passed through cooling cylinders to allow the polyurethane resin to cool and reach a form showing its true performance. Water-based polyurethanes are referred to as next-generation products. The production technology is very different.

Let us explain the most important advantages of the product in a few points:

• The product is classified as an environmentally friendly product because it has water content. • Since the resin in question is polyurethane, it is a high-performance product. • High adhesive strength (adhesion to any type of surface is provided with necessary modifications) • Wash fastness • High elasticity • High chemical resistance • High hydrolysis resistance • Ease of application; achieving high-performance product at very low viscosity. Therefore, the ease of use of low-viscosity product. • Possibility of adjustable viscosity for any type of application. Since Purin manufactures water-based polyurethanes in-house and with the experience it has gained over many years, it is able to design products specific to every type of application desired in the market. We started production of water-based polyurethanes (PUD) in 2018 and are diversifying our products in line with the needs we encounter in the sector. As a domestic company that has implemented current PUD technology, we would like to help you in all your water-based polyurethane product searches. İbrahim Kecin Senior Chemist General Manager PURİN Poliüretan