One-pack systems

Curing with Atmospheric Moisture. Type 2 in Table 2.5. High molecular mass polyaddition products of polyols with excess diisocyanate contain reactive isocyanate groups. They are used to formulate one-pack polyurethane paints that cross-link with the formation of urea groups under the influence of atmospheric moisture to produce paint films with excellent resistance to chemical and mechanical attack. Solvent-free products and dissolved products with isocyanate contents of 5- 15% (based on the solid resin) are commercially available. 

Since products that contain free isocyanate groups react with water, moisture may affect storage stability when producing pigmented coatings. This has to be prevented, and use of water-binding additives has proved effective (e.g., special monoisocyanates such as Additive TI (Bayer)). 

The resulting films have a very high mechanical resistance. They are particularly important for stone impact protection in automobile finishes, for coating high-quality industrial goods, for electrical insulation, as well as for coil coating applications. Solvent-free products are used in liquid form as thick-layer systems or in solid form for powder coatings. 

Aqueous Systems. Type 6 in Table 2.5. Aqueous dispersions of polyurethanes that are slightly supported by ionic groups also undergo physical film formation. The binder consists of polymer chains that are coupled via urethane and urea groups, and contain basic or acid groups. Neutralization by salt formation provides the necessary hydrophilicity if the self-emulsifying properties resulting from incorporation of hydrophilic polyether radicals are insufficient. 

Anionic dispersions based on IPDI, HMDI, and HDI are particularly important and are largely used for industrial applications (e.g., as glass fiber sizing or as a finish for leather and leather imitates). Chemical cross-linking is achieved by the use of water-soluble melamine resins. Stoving temperatures of ca. 140 °C are necessary. 

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One-pack systems (RTV-1 rubbers). These are very widely used for sealing and caulking applications. 

Moisture-curable urethane systems (one-pack) can be considered as two-component systems which use atmospheric moisture as the second component. One-pack urethane coatings can be produced that are similar in physical properties to the two-pack systems for almost all applications. These highly complex systems can have a great deal of flexibility. Claimed advantages are a one-pack system, rapid cure, even at low temperatures, excellent chemical and abrasion resistance and good flexibility. Although these systems have been available for some time in other countries of Europe, they are only recently beginning to be of interest in the UK. 

Also used with epoxy resins for adhesives is dicyanodiamide, H2N-C(=NH)NH-CN. It is insoluble in common resins at room temperature but is soluble at elevated temperatures and thus forms the basis of a one-pack system. 

A novel, latent curing system, which gives more than one year pot life at room temperature, has increased the use of epoxies for specialty adhesives and sealants, and for vinyl plastisols. The one-pack system provides fast cure when heated—for example 5 min at 100°C. 

In drying by polyaddition, low molecular mass reactive polymers such as alkyd resins, saturated polyesters, or polyacrylates react with polyisocyanates or epoxy resins to form cross-linked macromolecules. Because this reaction can take place at room temperature, the binder components must be mixed shortly before application. The period of time during which a coating of this type remains usable after mixing of the components is known as the pot life. These are known as two-pack coatings, differing from the one-pack systems, which can be stored for months or even years. 

One-Pack Systems 1 Oxidation with atmospheric oxygen solvent-containing up to 80 C... 

Systems with Polyisocyanates and Blocked Reactants. Type 7 in Table 2.5. Instead of blocking the isocyanate groups, they can be combined with latent reactants (e.g., oxazolidines) to obtain storage-stable one-pack systems. After application, curing is achieved not by heat, but by atmospheric moisture which induces ring opening and the formation of reactive hydroxyl and amino groups. 

Continuous efforts have therefore been made to develop binders for one-pack paints which must be completely compatible with active pigments such as zinc dust. Mixtures of ethyl silicate and zinc can be stored for unlimited periods in the absence of water. If the hydrolysis and condensation reactions caused by atmospheric moisture can be sufficiently accelerated during application of the coating, a one-pack system can be produced. 

The term reactive diluents denotes low molecular mass reactants that act as solvents with an extremely low volatility and participate in the cross-linking reaction. Reactive diluents have become especially important in one-pack systems because they can partially or wholly replace the solvent in high-solvent paints. Reactive diluents participate in the cross-linking reaction because their functional groups are identical or similar to those of the principal binder. They are completely incorporated into the polymer network during curing. Good compatibility with the principal... 

Epoxy adhesives are popular for retail or consumer applications. They may be supplied as liquids, pastes, putties, or as one-pack systems in stick form. Considerable ingenuity has... 

Lubricant one-pack systems for wood plastic composites, supplier product guide (vers. 1). Baerlocher GmbH September 2007. 

Uses Wetting agent, dispersant for coil coatings, OEM, general industrial, med.-high solid one-pack systems, acid-catalyzed systems, inks Properties Sp.gr. 1.02 g/cc dens. 8.53 Ib/gal acid no. 52 flash pt. (Seta) 44 C ref. index 1,460 52% NV... 

Another major trend in development is seen by the pelletisation of new antimony oxides blends. They extend the benefits of a one-pack system to flame retardants plus the non-dusting and feed benefits of a masterbateh. 

The use of lubricants with heat stabilizers, particularly lead types, in one-pack systems has not taken off in North America as it has in Europe. North America has focused more on the tin-based stabilizer systems, and customers still prefer buying the additives separately. 

Calcium-zinc stabilisers are rated as relatively nontoxic and are favoured for use in medical plastics, toys and food contact applications. They can be formulated as one-pack systems along with other additives to minimise handling problems. They normally have a self-lubricating role... 

One-pack or two-pack polyurethane surface coatings, which may sometimes be combined with acrylic resin systems. The one-pack system, which has a long shelf life, is an adduct of resin with polyisocyanate dissolved in a moisture-free solvent. When applied to a surface the film cures and hardens, as moisture in the air reacts with the isocyanate groups in the resin. The two-pack system consists of a polyisocyanate (frequently derived from an aliphatic isocyanate monomer) and a polyol as separate components. Once the two components are mixed, the shelf life is very limited. 

Lead one-pack systems Kickers for chemical blown foam... 

Because of their lesser ability to control shrinkage, the non-polar polymers such as polystyrene and polyethylene are often classified as low shrink rather than low profile additives. Usually, low profile additives are supplied as 30-40% polymer solutions in styrene monomer. Polyester resin manufacturers also package the low profile additives dissolved in their resins. These are referred to as one pack systems. As the industry has expanded, other thermoplastics have been identified which have shrinkage control properties. These are also now used commercially in a variety of applications. Examples of these other polyers are saturated polyesters, polyurethanes, stryene-butadiene copolymers and polycapro-lactones. Polyfvinyl acetate) based materials are probably still the most used low profile additives, being useful with the broadest range of unsaturated polyester resin structures. Relative proportions of the organics used in most formulations are 30-50% polyester alkyd, 10-20% thermoplastic and 40-50% styrene. 

MS polymers, silane-alkoxy-modified prepolymers of poly(propylene glycol), one-pack systems. Uses Many surfaces no primer necessary. 

Prepolymers with terminai isocyanate groups can react with and are hardened both with amino or hydroxyl compounds and with water. Hardening with water is preferred for one-pack systems, for which both atmospheric moisture and the film of water on the substrates act as hardeners for the prepolymer. Cross-linking with polyamines is particularly fast compared with curing by polyols. 

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