• Stable Coupling Agents and Crosslinkers for Aqueous Systems.
  Dr. Robert Johnston, Witco OrganoSilicones, Switzerland
• High Molecular Weight Polycaprolactone Copolyester-based TPUs.
  Joaquim Julià, Merquinsa Mercados, Spain
• New PU-based Raw Materials for Solvent Free Adhesives.
  Dr. Heinz-Werner Lucas, Bayer AG, Germany
• Understanding the Sprayability of Hot-Melt Adhesives.
  Olivier Georjon, Exxon Chemical Europe, Inc., Belgium

Biodegradability, compostability and repulpability have been important targets driving research and development of hot melt adhesives based on renewable raw materials. The challenge has been to provide these properties without significantly compromising on the critical performance requirements of hot melt adhesives. On the other hand, the special structural features of naturally derived materials such as stereochemistry, can provide enhanced properties for hot melt raw materials. For example, crystallinity conferred by monomer stereochemistry on lactide derived polymers can provide enhanced heat resistance to hot melt adhesives. Compostable hot melts based on appropriately substituted starches can be readily redispersed in water, a desirable property for a number of industrial applications. Thus polymers prepared from renewable raw materials can be designed to provide specific and desirable performance properties to hot melt adhesives. Examples of such polymers including performance properties and chemistry will be discussed.

Rhodia Chimie has formulated and patented a single proprietary family of water based nanolatex emulsions which do have the same penetration, consolidation performances as the solvent based ones. They can be used as a finished product or in formulation. This is a big interest for a market which requires more and more solvent-free products. These products show some specific particle size distributions, in order to optimise the penetration depth in the different substrates and the film forming ability on their surfaces. This approach is particularly efficient to obtain the required level of properties (adhesion, penetration, consolidation) on a wide range of substrates presenting different porosities. In the present paper we will illustrate the characteristic and results of these new products in their main applications fields, like coating primering, substrate consolidation, flooring primering, concrete anti- efflorescence treatment.

Vinylacetate/Ethylene copolymer dispersions have as a result of their extraordinary properties found several uses as adhesives raw material, ranging from packaging, flooring to pressure sensitive adhesives. Besides their good tackifying properties also on difficult surfaces, the VAc/Et dispersions can be produced with a very low content of VOCs, so that further production of low-emitting adhesives for indoor use is possible.
The impact of the composition of the copolymers, the use of different emulsifiers and/or protective colloids will be discussed. Copolymerisation of long component acrylics or vinylesters of versatic acid as terpolymer component as well improves properties like tack, final adhesion and heat stability.

Dow has recently developed several new and exciting technologies which will further improve physical properties and processing ranges and thus extend the use of polyurethane beyond its current sphere of activity. This paper will focus on the following technologies and their benefits for the ACES (Adhesives, Coatings, Elastomer & Sealants) markets: high temperature resistance for flexible polyurethane production, up to 155 °C; polyols for curing at room temperature; extended potlife for polyether polyols with maintained curing degree; hot melts based exclusively on polyethers and methylene diisocyanate (MDI); controlled reactivity MDI; 100% water blown 2k PU foams.

In the last decades an impressive growth of demand in the field of latecies for adhesives production has driven the development of a rational approach to the design and control of the polymerisation processes. Macromolecules are characterised by a complex architecture that is linked to the end-use properties of the final product. A suitable control of the reaction parameters is a necessary condition to govern polymer qualities, but it requires a deep understanding of diverse topics such as Polymer Chemistry, Standard Thermodynamics, Reaction Kinetics, Colloid Science and Reaction Engineering. In this intricate scenario, good and reliable models represent a fundamental tool for the solution of this problem. In order to explain the potential of the model, in this paper some significant aspects concerning polyvinyl acetate emulsion polymerisation will be illustrated.

Certain metals require a surface pre-treatment to achieve highly durable bonded joints. This e.g. is the case when adhesively bonding aluminium and its alloys or stainless steel. With regards to joint properties suitable surface pre-treatments such as chromic acid anodising or pickling etching are well known from aerospace industry. These "wet pre-treatments" suffer from some major disadvantages such as environmental issues, their long pre-treatment times and the necessity to pre-treat the whole submerged surface. The newly developed and patented CLP (Ciba Laser Pre-treatment) avoids these disadvantages of "wet pre-treatments". It consists of only two process steps, an initial primer application followed by a laser treatment . CLP facilitates bonded joints with excellent or even superior joint durability and combines that in a unique manner with processing benefits and significant ecological advantages. With the ability for selective pre-treatment of the bonding areas only CLP allows for reduced pre-treatment times and offers the potential to reduce the pre-treatment costs.

Film laminates for flexible packaging are gaining steadily increasing market shares in the packaging industry. The present adhesives for the lamination process are two component polyurethanes that are applied either as organic solutions, or as solventless systems. BASF has developed a novel acrylic dispersion, that combines the advantages of ecological and toxicological safety with a high standard of technical performance. The dispersion, Acronal DS 3505 X, is a raw material for one component adhesives, that do not require the addition of isocyanate or other crosslinking agents to get attractive peel strengths of the laminate. A special feature of Acronal DS 3505 X is its high compatibility with printing inks being coated on laminating films and coming into direct contact with the adhesive. Investigations including electron microscopy have shown that the penetration of the adhesive into the printing ink coating is substantial for this benefit.

Organofunctional silanes have been commonly employed as coupling agents and crosslinkers to improve adhesion and durability of coatings, adhesives and sealants. Silane adhesion promoters in waterborne systems had limited success due to their inherent reactivity and instability in water. Novel waterstable silanes have now been launched that allow for silane containing latex systems with significantly improved shelf lives, leading to superior adhesion performance, enhanced mechanical properties and improved chemical resistance.

This paper is based on a study of the main advantages and performance of new, high molecular weight TPUs based on polycaprolactone copolyesters. These products are new developments, still patent pending. In comparison with other polyesters and polymers, which are all used in the adhesives market, and focusing the thermobonding (heat sealing) adhesives for textile applications, as well as the additives for reactive hot melts, they have two important advantages: a higher crystallinity and lower viscosity at melting point, and the possibility of using them in powder form. The paper emphasises the use of these products in powder form, in thermobonding applications, whereby the use of organic solvents (included in the VOC list) is avoided, following the "sustained growth" tendency.

Of all known adhesive raw materials, polyurethanes form the basis for the manufacture of the broadest variety of adhesive types: solvent-based, water-based, reactive 100% solids, hot melt. Whereas solvent-based PU adhesives have been known and established for several decades, others, e.g. water-based, hot melts, have only recently found broader application. The reasons for the success are (i) the intrinsic adhesion, bonding and processing characteristics and (ii) the formation reaction, which being a polyaddition, allows relatively easy adjustment of the properties. The rheological behaviour (i.e. activation), which is time and temperature dependent, is one of the important features of PU systems. By using several state-of-the-art investigation methods (i.e. the Bayer-developed Hot-Tack-Tester, Bohlin rheometer), further basic insights into the physico-chemical behaviour of PU systems could be gained. From these investigations it was possible to develop new products for water-based, solvent-based, reactive and hot melt powder adhesives. In addition, new aliphatic and aromatic prepolymers with very low monomeric content offer new formulating opportunities and support the need to meet regulatory demands. Thus new raw materials and improved know-how can support the adhesive industry which faces new technical, ecological and regulatory demands.

High-productivity spraying processes, such as melt-blown or Controlled Fiberization, are expanding at a rapid pace in the Hot-Melt Adhesives industry. Yet, the materials parameters governing these processes are still unknown, and improving sprayability often resumes to tedious trial-and-error approaches. In this work, we first carry out a dimension analysis of the spraying process, and demonstrate that the processing problems occur during the strong and fast extensional flow encountered by the stretched filament. Then, we describe a gram-scale rheological experiment providing a quantitative criterion that correlates with spraying behaviour. We show that the spraying process is limited by the cohesive break of the HMA filament, which suggests that low melt elasticity is needed for optimum sprayability. As an important consequence, polymers having narrow molecular weight distribution, such as metallocene catalyzed Exact® plastomers (M_u/M_n-2) or Vector® styrenic block copolymers (M_u/M_n-1) offer optimum sprayability.