Cobalt naphthenate polyester resin

Ketone Peroxides. These materials are mixtures of compounds with hydroperoxy groups and are composed primarily of the two stmctures shown in Table 2. Ketone peroxides are marketed as solutions in inert solvents such as dimethyl phthalate. They are primarily employed in room-temperature-initiated curing of unsaturated polyester resin compositions (usually containing styrene monomer) using transition-metal promoters such as cobalt naphthenate. Ketone peroxides contain the hydroperoxy (—OOH) group and thus are susceptible to the same ha2ards as hydroperoxides. 

Cobalt salts are used as activators for catalysts, fuel cells (qv), and batteries. Thermal decomposition of cobalt oxalate is used in the production of cobalt powder. Cobalt compounds have been used as selective absorbers for oxygen, in electrostatographic toners, as fluoridating agents, and in molecular sieves. Cobalt ethyUiexanoate and cobalt naphthenate are used as accelerators with methyl ethyl ketone peroxide for the room temperature cure of polyester resins. 

The binder itself (Genpol A-20 polyester resin, styrene and methyl acrylate) was combined with the necessary polymerization catalyst (methyl ethyl ketone peroxide) and an accelerator (cobalt octoate or naphthenate). 

The two most important peroxy materials used for room temperature curing of polyester resins are methyl ethyl ketone peroxide (MEKP) and cyclohexanone peroxide. These are used in conjunction with a cobalt compound such as a naphthenate, octoate, or other organic-solvent-soluble soap. The peroxides are referred to as catalysts (though, strictly speaking, these are polymerization initiators) and the cobalt compound is referred to as an accelerator. 

Unsaturated polyester resins are mainly made by condensing a dibasic acid (1,2-propanediol) with an anhydride (maleic or phthalic anhydrides), by forming ester linkages between the dibasic acid (or their anhydrides) and glycols. Then a reactive monomer (mostly styrene or vinyl toluene, MMA or diallyl phthalate) is used to crosslink the system when needed. Unsaturated denotes the uncompleted chemical activity (double bond) in the original structure, which are used for crosslinking afterwards. In this context, an excess of styrene as the crosslinker (10 to 50 %) is usually added to have it ready in the system, as well as to reduce the viscosity. There are also certain accelerators used (such as, cobalt naphthenate or tertiary amines like dimethyl aniline) to facilitate the cure at ambient temperatures. In addition, there may be pigments, fillers, various inhibitors, accelerators, stabilisers and flame retardants, added to the system. Polymerisation is activated whenever a catalyst (i.e., benzoyl or methyl-ethyl-ketone peroxide) is added. 

An organic Co compound is generally used as an accelerator and cobalt octoate (10% Co content), or cobalt naphthenate (6% Co content) are the most commonly marketed products. Polyester resins can also be supplied pre-accelerated. The accelerator is always added first and used in conjunction with a peroxide catalyst for room temperature curing. Organic peroxides are hazardous materials and must be handled strictly in accordance with the recommended safety precautions. 

Methyl ethyl ketone peroxide (MEKP, MED, and peroxide) n. A complex peroxide mixture made by reacting hydrogen peroxide with MED, with the approximate formula (CH3C00C2H5)3. MEKP is an initiator for free-radical polymerization and a curing agent for polyester resins. In combination with an accelerator such as cobalt naphthenate, MEKP can bring about cure at room temperature. Because... 

Naphthenic acid n, A carboxylic acid derived from petroleum refining and usually one of a mixture of similar compounds. The mixed acids and some of their soaps, e.g., cobalt naphthenate and calcium naphthenate, are useful as catalysts or accelerators in curing polyester resins and as drying agents in paints and varnishes. Commercial naphthenic acids are not pure compounds, but consist of a mixture of acids based on cyclopentane rings. 

Schena has seen a lymphomatoid-like contact dermatitis (in a marble-factory worker) from cobalt naphthenate, used as an accelerant in polyester resins... 

Two types of conunercially available jute fabrics were used Hessian cloth with starch and Hessian cloth without starch. Isophthalic polyester resin was used as matrix. Metltyl ethyl ketone peroxide (MEKP) and cobalt naphthenate were used as catalyst and accelerator, respectively. Calcium carbonate (200 mesh) was used as filler. 

The most common accelerators for methyl ethyl ketone peroxide and cyclohexanone peroxide are salts of metals which exhibit more than one valency. The most widely used metal of this kind is cobalt, although salts of cerium, iron, manganese, tin and vanadium also find some application. In order to be effective as an accelerator a metal salt must be soluble in the polyester resin. The most commonly used salts are naphthenates, which are readily soluble octoates also may be used. (Naphthenic add is extracted from the gas oil and kerosene fractions of petroleum and consists of a complex mixture of carboxylic acids of substituted cyclopentanes and cyclohexanes. ) The decomposition of a hydroperoxide (ROOH) by a metal salt such as cobalt naphthenate to give free radicals proceeds according to the following chain reaction ... 

Fig. 26 Plots of dynamic and loss moduli versus curing time for unsaturated polyester. Amount of accelerator (cobalt naphthenate), I-l (0.06g/I00g resin), 1-2 (0.024), 1-3 (0.012), and 1-4 (0.006). (From Ref. 28.)...

UPRs based on a mixture of maleic anhydride, phthalic anhydride and adipic acid in a molar ration of 1 2 2 were prepared in the presence of the polyesterification catalysts, i.e. lead dioxide, p-toluenesulfonic acid monohydrate and zinc acetate dihydrate, and next crossHnked with styrene by using MEKP as the initiator and cobalt naphthenate (CoNp) as the promoter [197]. Most often, the catalysts used in the polyesterification process cannot be easily separated from the polyester, thus the effect of the residual catalysts on the curing process and color of the cured polyester resin should be taken into account. It was shown that the residual catalyst could affect the curing reaction even in a small amount (Table 28), increasing the activation energy a, frequency factor ko and the reaction order x. 

Unsaturated polyester resin Polimal 1201P, produced by Organika-Sarzyna Co. Poland, was of the izophthalate/maleate/propylene glycol type. UPR (styrene solution) was cured by mixing with methyl ethyl ketone peroxide and cobalt naphthenate. 

These are chemicals whose function is to produce a crosslinked, thermosetting plastic from an initially linear or branched polymer. For example, a vinyl monomer, such as styrene, a free-radical initiator, and sometimes a promoter (e.g., cobalt naphthenate, to speed up the reaction) can be dissolved in a low molecular weight unsaturated polyester resin, which forms crosslinks by an ordinary addition mechanism involving the double bonds in the polyester (Example mprb2.3). Curing is also important in forming tires, as sulfur is compounded with natural, butadiene, or isoprene mbber to form a crosslinked rubber. 

The condensation of an alcohol with an acid to give an ester with water as a by-product is a classical way to make polymers (Table 17.1,1). In alkyd resin cooking (Section 13.4), it was mentioned that additional reactions are those between anhydride and alcohol or epoxide and between free acid and alcohol and esters (transesterification). The simple polyester with its repeating dyadic structure can be dissolved in styrene (about 70 parts polyester to 30 parts styrene) and polymerized at room temperature by a free-radical route using a redox couple. (Methyl ethyl ketone peroxide plus cobalt naphthenate would be typical.) Glass-reinforced boat hulls and automobile bodies are made from such systems. In some cases, monomers more expensive than styrene can be justified. Methyl methacrylate, triallyl cyan-urate, and diallyl phthalate have been suggested by various sources. Flammability... 

Similar to the vegetable oil-based polyesters, the curing system must be selected according to the nature of the oil. As an example, for non-drying oil-based poly(ester amide), the following system can be used. A homogeneous mixture of resin with 30 parts of styrene or methyl methylacrylate as the reactive diluent, four parts of methyl-ethyl ketone peroxide (MEKP) as an initiator and two parts of cobalt octate/naphthenate as an activator, are prepared in a container at room temperature by mechanical stirring. The thin films of the resin system can then be cured at the desired temperature for a predetermined period of time. 

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