Other Types of Coupling Agents

Mascia [3] mentions the following types of coupling agents or adhesion promoters, besides organotitanates  

Phosphorus-containing compounds. They are used to aid adhesion of polymers on metal substrates because of their chelating action toward metal ions. 

Acids such as stearic acid, salicylic acid, and p-chlorophenyl-substituted fatty acids. 

Amines, i.e., piperidine derivatives, because the polar amino groups are not sterically hindered and can therefore provide good alignment on the surface of substrates. 

Chromium coordination complexes with compounds containing — NH2, — NH—, epoxide, amide, and isocyanate groups [52-54] are also used. Cation active substances such as cationic styrene aminosilanes are recommended by Dow Coming (U.S.) as coupling agents. For example. 

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Other types of coupling agents include 1,2-diketones for steel,27 nitrogen heterocyclic compounds such as benzotriazole for copper,28,29 and some cobalt compounds for the adhesion of brass-plated tire cords to rubber.30... 

On further examination, over half of the AST patents listed were classified as associative in this review. Although most of these occur in more recent years, the earliest found (59) happens to be the first entry in the tables. In this and four other former issues (62, 64, 69, 70) that differ in the type of hydrophobic monomer employed, a maleic-anhydride-con-taining prepolymer is prepared and subsequently post-esterified with a nonionic surfactant. In essence, the associative side chains are grafted onto the polymer backbone. In nearly all of the other associative patents, the associative monomers are synthesized first and then copolymerized with the carboxylic acid and hydrophobic monomers. Many similarities also exist between the various associative AST patents. In refs. 62, 64, 69, and 70, the hydrophobic monomer was an obvious variable. In some others, differentiation is a manifestation of the type of coupling agent used. 

The main types of coupling agents in commercial use are described further. Most, if not all of them, have other applications, mainly in the wider adhesive and dispersant markets. The discussions here are limited to their use as coupling agents. It is worth noting... 

A somewhat different type of coupling is observed when salts of (i-keto esters, arylacetonitriles (ArCH2CN), and other compounds of the form ZCH2Z are treated with an oxidizing agent such as iodine," " or Cu(II) salts." Arylmethanesulfonyl chlorides (ArCH2S02Cl) couple to give ArCH=CHAr when treated with Et N." ... 

The coupling agents which have been most extensively used are various organo-silicon compounds, although several other types of compound of quite different chemistry, including zirconium and titanium comlexes [1], have also been used. It is with silane materials that we are concerned here. 

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