Cresol-formaldehyde plastic

Phenolic plastics. Collective designation for phenolic resin-based plastics. Phenolic resins are produced by condensation of phenol and/or its homologues, such as cresol, with an aldehyde, such as formaldehyde or with an aldehyde-releasing material such as hexamethylenetetramine. Phenol/formaldehyde and/or cresol/formaldehyde resins are used as binding materials in fibre board, laminated paper and fabrics. In phenolic moulding compounds, the proportion of filler (such as wood flour, rock flour, asbestos, stone powder, mica, glass fibre) can be equal to that of the resin. These thermosets can be processed by compression or injection moulding into black or dark-coloured products mainly for the electric industry. 

The monomer is obtained by reacting bisphenol A with epichlorohydrin. Compounds with q = 0.1-0.6 are liquids, those with q = 2-12 are solids. Other epoxide resins are based on epoxidized phenol/formaldehyde and cresol/formaldehyde resins, or on cycloaliphatic or heterocyclic structures. Commercially available epoxide resins are generally compounded, that is, they also contain plasticizers, diluents, pigments, etc. 

Cresol kre- s61 [ISV, irreg. fi. cresote] (ca. 1869) (hydroxytoluene, methylphenol) n. H3CC6H4OH. An important family of coal-tar derivatives, occurring in ortho, meta, and para isomers, and used in the production of phenol-formaldehyde resins and tricresyl phosphate, an important plasticizer for PVC. Three cresols are possible, namely (a) o-cresol, mp 30°C bp, 19rC (b) m-cresol, mp 4°C bp, 205°C (c) p-cresol, mp 36°C bp, 201°C, and these are found together in the crude cresylic acid from coal tar. The main use of the cresols is in the manufacture of cresol-formaldehyde resins, and cresylic acid, rich in the meta isomer, is usually chosen for this purpose. 

Methylphenol is converted to 6-/ f2 -butyl-2-methylphenol [2219-82-1] by alkylation with isobutylene under aluminum catalysis. A number of phenoHc anti-oxidants used to stabilize mbber and plastics against thermal oxidative degradation are based on this compound. The condensation of 6-/ f2 -butyl-2-methylphenol with formaldehyde yields 4,4 -methylenebis(2-methyl-6-/ f2 butylphenol) [96-65-17, reaction with sulfur dichloride yields 4,4 -thiobis(2-methyl-6-/ f2 butylphenol) [96-66-2] and reaction with methyl acrylate under base catalysis yields the corresponding hydrocinnamate. Transesterification of the hydrocinnamate with triethylene glycol yields triethylene glycol-bis[3-(3-/ f2 -butyl-5-methyl-4-hydroxyphenyl)propionate] [36443-68-2] (39). 2-Methylphenol is also a component of cresyHc acids, blends of phenol, cresols, and xylenols. CresyHc acids are used as solvents in a number of coating appHcations (see Table 3). 

Phenol-formaldehyde (phenolic) plastics The chemical resistance is affected by the phenol used, cresols giving the best acid resistance whilst xylenols are often used to obtain the best alkali resistance. For chemical-resistant applications the fillers used in moulding powder and reinforcing material in laminates should be inorganic, e.g. asbestos or glass. The resins are usually dark in colour. 

Phenolics. These plastics allow the preparation of both random prepolymers, such as Baekelands A stage and true structopendant prepolymers, commonly known under the term novolaks (Figure 6). Novolaks permit one to take advantage of the newer prepolymer technology. Monomers are phenol, cresols, and formaldehyde. Molecular weights of the novolaks are between 300 and 700. Novolaks are obtained through careful selection of reaction conditions and catalysis of the phenol-formaldehyde reaction. Molecular weight, as well as the ratio of 2,2 - and 2,4 -links, can be controlled. These structural factors, studied extensively by Wood (28), have an eflFect on the physical properties of the cured polymer network. 

The mixture of cresols obtained from coal tar is called cresylic acid, an important technical product used as a disinfectant and in the manufacture of resins and tricresyl phosphate. Cresols are useful as raw materials for various chemical products, disinfectants, and synthetic resins. The isomer o-cresol is a starting material for the herbicides 4,6-dinitro-o-cresol and 2-methyl-4-chlorophenoxyacetic acid. The isomers w-cresol and p-cresol are used in phenol-formaldehyde resins and are converted to tricresyl phosphate (a plasticizer and gasoline additive) and to di-t-butyl cresols (antioxidants called BHT). 

The commonest of these occur in industrialized and urban areas where discharges from indnstry canse the snrface water (and groundwater to a lesser extent) to be contaminated with phenol or its derivatives, like cresol. Examples include the manufacture of certain herbicides or their precursors, the pulp and paper industry, the manufacture of phenol for use in plastics, such as phenol-formaldehyde, the manufacture and use of pentachlorophenol as a wood preservative, use of phenol derivatives (cresol, etc.) in hospitals, etc. The runoff of these compounds to surface waters and seepage to the groundwater are enlarged in rainy seasons in many Asian cities. 

Abundant byproducts of the Coalite process were also low temperature tars, containing cresylic acids (cresols the products were referred to as meta cresol and cresylic acid). With the sudden increase in the price of phenol around 1937, and further rises in 1938, both as a result of demand from the plastics industry (despite a general downturn in trade), it was suggested that Low Temperature Carbonisation Ltd. investigate catalysts suited to condensations of cresylic acids (as an alternative to phenol) with formaldehyde. Certainly there was a greater dependence in Britain on cresylics than was the case in the United States, because of their availability from coal-based processes. In the meantime Monsanto, which manufactured coal tar cresols (as did Yorkshire Tar Distillers), was considering the erection of a second British synthetic phenol plant. 

This high reactivity is especially essential for the production of phenol/formal-dehyde condensation products (Bakelite resins) phenol/formaldehyde resins were the first synthetic plastics, with production patented by Leo H. Baekeland in 1907. In addition to phenol, cresols, xylenols and long-chain alkylphenols are used to obtain special quality characteristics. Phenolic resins are used widely for numerous applications. Phenolic resin production in Western Europe in 1985 was around 500,0001, in the USA 1,150,0001 and in Japan 325,0001. 

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