Reactive latexes

In the development of water-borne coatings, a main area of current research activities is the crosslinking of the polymer film. Traditionally, solvent-based coatings yield a crosslinked film after the drying process, whereas water-borne coatings result in a thermoplastic polymer film. The result of this is that, for example, solvent resistance of solvent-based coatings is superior to that of water-borne coatings. 

It is well-known that the process of cohesive strength development in a water-borne polymeric coating consists of three main mechanisms  

This process of cohesive strength development is the final stage in the complex process of film formation. The two preceding stages are the evaporation of water and the coalescence of the latex particles. These two stages have been investigated extensively, and a few different models have been proposed to describe these physical processes. 

The first process of interest in the cohesive strength development is the interdiffusion of polymer chains. It is well-known that the diffusion of polymer chains in a polymer matrix is strongly dependent on the molar mass of the chains. In terms of development of the cohesive strength, two opposing effects can be recognised  

The method of crosslinking determines to some extent the requirements with respect to polymer-polymer interdiffusion. 

---

Chemical Grafting of Oligonucleotides Onto Reactive Latex Particles... 

A large number of processes have been developed during the last decade, permitting the synthesis of reactive latexes and the functionalization of prepared polymer particles with specific properties ... 

Postreaction on reactive latexes This process is very useful for modifying the functionality of given latex if it cannot be obtained directly. 

R. A. Dickie and S. Newman, Rubber-Modified Thermosets and Processes, U.S. Pat. 3,833,682 (1974). Semi-I and IPN latexes with reactive shells. Graded composition latexes containing rubber cores. Thermoset expoxies, etc. containing reactive latexes. One of three closely related patents. See U.S. Pat. 3,833, 683 (1974) and 3,856,883 (1974). 

Latex 735A contains a sol polymer which gives the longest dry open tack time of all the latexes. Its films are also the most readily heat reactivated. Latex 735A is generally used in adhesives for wet laminating. 

The advantage of the low Cex RCTAs is that latexes with controlled particle size distributions using seeded polymerisations can be made. These latex particles in a second stage polymerisation can be further reacted with other monomers to make block copolymers with core-shell particle morphology or even latex particles in which the second block has functional groups, that is, reactive latexes (Monteiro de Barbeyrac, 2002). 

In mass polymerization bulk monomer is converted to polymers. In solution polymerization the reaction is completed in the presence of a solvent. In suspension, dispersed mass, pearl or granular polymerization the monomer, containing dissolved initiator, is polymerized while dispersed in the form of fine droplets in a second non-reactive liquid (usually water). In emulsion polymerization an aqueous emulsion of the monomer in the presence of a water-soluble initiator Is converted to a polymer latex (colloidal dispersion of polymer in water). 

Waterborne contact adhesives contain an elastomer in latex form, usually an acryflc or neoprene-based latex, and a heat-reactive, cross-linkable phenohc resin in the form of an aqueous dispersion. The phenoHc resin improves metal adhesion, green strength, and peel strength at elevated temperature. A typical formulation contains three parts latex and one part phenohc dispersion (dry weight bases). Although metal oxides may be added, reaction of the oxide with the phenohc resin does not occur readily. 

Silicones. Commercially avaHable sHicone sealants are typicaHy one of three curing types moisture-reactive (curing) sealants, moisture-releasing (latex) sealants, and addition-curing sealants. Of these three types, moisture-curing sHicones make up the vast majority of sHicone sealants sold. 

The carboxylated latexes are formulated to use a reduced amount of a less reactive 2inc complex. Special resin blends provide an optimum balance of film tack and strength, and are coUoidaHy compatible with the carboxylated latexes (158). Epon resins may also be used as an acid acceptor in place of 2inc oxide (160). 

Using magnesium ether carboxylates as emulsifier a porous polyvinylchloride can be made [218] and a propoxylated ether carboxylate is described as emulsifier to make an ethyl acrylate-styrene copolymer [219]. A crosslinked latex with a three-dimensional network is achieved by polymerizing an ethylenically unsaturated monomer with a reactive saturated monomer using ether carboxylate as emulsifier [220]. 

Polymeric particles can be constructed from a number of different monomers or copolymer combinations. Some of the more common ones include polystyrene (traditional latex particles), poly(styrene/divinylbenzene) copolymers, poly(styrene/acrylate) copolymers, polymethylmethacrylate (PMMA), poly(hydroxyethyl methacrylate) (pHEMA), poly(vinyltoluene), poly(styrene/butadiene) copolymers, and poly(styrene/vinyltoluene) copolymers. In addition, by mixing into the polymerization reaction combinations of functional monomers, one can create reactive or functional groups on the particle surface for subsequent coupling to affinity ligands. One example of this is a poly(styrene/acrylate) copolymer particle, which creates carboxylate groups within the polymer structure, the number of which is dependent on the ratio of monomers used in the polymerization process. 

---