Zircoaluminates

Various inorganic esters have been claimed as coupling agents for reinforced plastics, including aminobenzyl phosphonates, dicetylisopropylborate, alkoxy compounds of aluminum, zirconium and titanium, zircoaluminates, and numerous substituted titanates [1]. These metal alkoxides could function in a similar manner to the orthosilicates by reacting with hydroxylated substrates. Like the simple orthosilicates such as tetraethyl orthosilicate (TEOS), it is less evident how an-... 

Cohen has presented a series of papers on the extremely interesting and versatile zircoaluminates [13]. The structures of these compounds are not known with certainty, but various structures have been put forward and one such suggestion is shown in Fig. 7. Typically, these zircoaluminates are solvent-soluble, but can be used in aqueous solution in combination with various aqueous zirconium compounds. 

Hunt et al. [ 17] have investigated the role of various coupling agents, such as zirconates, titanates, and zircoaluminates, in zirconia-polypropylene suspensions for use in the production of ceramics by injection moulding. All the coupling agents were observed to reduce the melt viscosity. 

Keyvrords Zircoaluminates adhesives polyester coating alkyd coating rubber high shear mixer. 

In 1983 a new class of metal organic adhesion promoters—the zircoaluminates— emerged. Evaluations by all of the major glass manufacturers ultimately provided compelling evidence that zircoaluminate application to fiberglass did not result in the sine qua non for success, that is, the irreversible attachment to the glass surface in the presence of moisture. (Note Irreversible is not intended to mean the... 

Zircoaluminates (ZAs) constitute a unique class of bifunctional additives which are synthesized in accordance with a highly specific procedure [4-6] to produce stable covalent molecules. As shown below, the essential chemistry involves the reaction of two solid inorganic raw materials with a number of different functionalized carboxylic acids in the presence of selected solvents [reaction (2)]. 

The product mix (Table 1) is observed to vary as a function of both the solvent in which the product is synthesized and the organofimctional group. Appropriate selection will depend on the resin component of a system and also on the zircoaluminate solvent which will determine the dispersibility of the active component and thereby the performance (see Section 4.2.2). 

T-peel strengths or EPDM bonded with zircoaluminate or silane-containing adhesive"... 

Formulation component Kraton G1650, 65 parts Kraton G 1657, 35 parts Neville LX-685,60 parts Piccofyn A-l 35, 60 parts Picovar AB165,65 parts zircoaluminate, 4-6 parts. 

Figure 1. Postulated mechanism for enhanced adhesion by zircoaluminates.

Zircoaluminates are predominantly inorganic (50-75 wt%) metal organic adhesion promoters in contrast to the silanes (< 50%). As such, they are highly polar and do not dissolve appreciably or disperse easily in resin/solvent-based media. Thus, the user must employ a high shear mixer (Cowles in paint manufacture, Banbury in rubber manufacture) to achieve as fine and homogeneous a dispersion of ZA as possible within a given system. 

Zircoaluminate adhesion promoters constitute a novel class of compounds which have proven themselves useful in arresting corrosion on coated metals, enhancing adhesion of adhesives to rubber and metal, and improving bonding of formed rubber articles containing ZA to other substrates. 

The filler surface treatment can also be applied as an additive to the adhesive formulation. Coupling agents, such as organotitanates, zircoaluminates, or organosilanes, are added to the formulation so that they preferentially find their way to the filler s surface and provide for optimal surface chemistry and adhesion between the filler and the matrix resin. These coupling agents are discussed in Chap. 10. 

Zirconium propionate Zircoaluminates Zirconium acetylacetonate, zirconium methacrylate... 

Zircoaluminates, introduced in 1983, claim performance at least comparable to that of silanes at substantial cost savings. Several functionalities are available. They are stable and soluble in an aqueous environment and do not require the presence of water to function. The surface reaction is irreversible. Among the fillers treated successfully are silica, clay, calcium carbonate, alumina trihydrate, and titanium dioxide. 

Chem. Deserp. One-part, water-based epoxy resin with conosion inhibitors Bisphenol /Vepichlorohydrin epoxy (< 10%), bisphenol A novolac epoxy resin (< 10%), ethanol (2-10%), propylene glycol (5-15%), carbo) zircoaluminate sol n. (< 5%), etc. 

Wollastonite siufaces react with water and hydrolyse to form calcium hydroxide. The mineral is attacked by strong mineral acids, especially hydrochloric acid, and by certain organic acids. Siuface treatment can be carried out with silanes, titanates or zircoaluminates. 

Organotitanates, aluminates, zirconates and zircoaluminates can also act like silanes as adhesion promoters. They perform similar functions, but unlike silanes there is no need for water molecules to be eliminated. These other treatments bond the polymer to the filler surface by a chemical bond involving proton co-ordination, and they can also be used with fillers that are not receptive to silanes, such as calcium carbonate, carbon black and barium sulfate, as well as barium ferrite, magnesium hydroxide, aluminium trihydroxide, titanium dioxide, talc and the nanoclays. 

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