Formaldehyde polymeric products

Primary aromatic amines react with aldehydes to form Schiff bases. Schiff bases formed from the reaction of lower aUphatic aldehydes, such as formaldehyde and acetaldehyde, with primary aromatic amines are often unstable and polymerize readily. Aniline reacts with formaldehyde in aqueous acid solutions to yield mixtures of a crystalline trimer of the Schiff base, methylenedianilines, and polymers. Reaction of aniline hydrochloride and formaldehyde also yields polymeric products and under certain conditions, the predominant product is 4,4 -methylenedianiline [101 -77-9] (26), an important intermediate for 4,4 -methylenebis(phenyhsocyanate) [101-68-8], or MDI (see Amines, aromatic amines, l thylenedianiline). 

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acryHc (52). The acryhc-vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aHphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, soHd epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

Polymer (184) has a network structure and was obtained by reaction of dibenzo-18-crown-6 with formaldehyde in formic acid. Amongst the alkali metal ions, it selectively captures K+ and Cs+ from methanol or methanol/water. A related polymeric product has been reported (as a gel) from the reaction of this crown with formaldehyde in chloroform using sulfuric acid as catalyst (Davydova, Baravanov, Apymova Prata, 1975). 

Substance made of giant molecules formed by the union of simple molecules (monomers) for example, polymerization of ethylene forms a polyethylene chain, or condensation of phenol and formaldehyde (with production of water) forms phenol-formaldehyde resins. 

The polymerization products of propylene have been observed to be saturated hydrocarbon polymers and terpenelike unsaturated hydrocarbons (Kuhn, 64). The condensation of formaldehyde with phenols and cyclohexanols by means of aqueous hydrogen fluoride has also been observed (Badertscher el al., 65). 

In 50% aqueous dioxane and acidic conditions, lignin reacts with formaldehyde at positions 2 and 6 to give methylene crosslinks which result in the formation of a gelled or polymerized products (Fig. 8). The usefulness of mefa-hydroxy methylated lignin was illustrated by the... 

The basic amino group of the 1-position in semicarbazide or thiosemi-carbazide may be used to react by a substitution reaction with activated halides [52], ethers [51], hydroxy [53], phenoxy [54], and amino groups [55] to yield substituted 1-semicarbazides or thiosemicarbazides. In addition, the amino group of the 1-position may add to electron-deficient double bonds [56]. Formaldehyde and other aldehydes may add to all the available free NH groups to give methylol, alkylol, or polymeric products under basic conditions [57]. Aldehydes or ketenes usually give semicarbazone derivatives, and these in turn are used analytically to identify the purity or structure of a known aldehyde [3]. 

In spite of Baekeland s success, it was another two decades before the Age of Polymers can really be said to have been born. The 1920s and 1930s saw the invention and/or commercialization of a number of new polymeric products ("plastics") that most consumers now consider to he essential chemicals in their lives. These products include the urea formaldehyde plastics (1923), polyvinyl chloride (PVC 1926), polystyrene (1929), nylon (1930), polymethylmethacrylate (acrylics 1931), polyethylene (1933), the melamine plastics (1933), polyvinylidene chloride (Saran 1933), polyvinyl acetate (PVA 1937), and tetrafluoroethylene (Teflon 1938). 

Fig. 7-25. Main reactions of the phenolic /8-aryl ether structures during alkali (soda) and kraft pulping (Gierer, 1970). R = H, alkyl, or aryl group. The first step involves formation of a quinone methide intermediate (2). In alkali pulping intermediate (2) undergoes proton or formaldehyde elimination and is converted to styryl aryl ether structure (3a). During kraft pulping intermediate (2) is instead attacked by the nucleophilic hydrosulfide ions with formation of a thiirane structure (4) and simultaneous cleavage of the /3-aryl ether bond. Intermediate (5) reacts further either via a 1,4-dithiane dimer or directly to compounds of styrene type (6) and to complicated polymeric products (P). During these reactions most of the organically bound sulfur is eliminated as elemental sulfur.

Reductive alkylation of primary arylamines with an aldehyde is often accompanied by side reactions leading to polymeric products, especially with formaldehyde. Gradual addition of an aldehyde to an amine in order to maintain low concentrations of the aldehyde is an effective procedure for minimizing the side reactions.41 Thus, Bonds and Greenfield obtained high yields of (V,(V-dimethylarylamines by the reductive alkylation of primary arylamines with formaldehyde over Pd-C by gradually adding an... 

Chlorinated phenols are common environmental pollutants, introduced as pesticides and herbicides. Studies have been carried out on the potential use of radiation to destroy these compounds as a means of environmental cleanup . While these studies were concerned with mechanisms (and are discussed in the chapter on transient phenoxyl radicals), other studies involved large-scale irradiation to demonstrate the decomposition of phenol in polluted water . Continuous irradiation led to conversion of phenol into various degradation products (formaldehyde, acetaldehyde, glyoxal, formic acid) and then to decomposition of these products. At high phenol concentrations, however, polymeric products were also formed. 

The commercial importance of phenol-formaldehyde resins has resulted in extensive studies of these systems, with the aim of identifying the reaction mechanisms and intermediates that occur during subsequent polymerization reactions. However, the complexity of Novolac-type systems has made a detailed understanding of the subsequent chemical processes and their relationship to the physical properties of the final polymerized product difficult. Thus, it is necessary to simplify the system in order to more readily unravel this complexity. Model compounds are frequently used to understand complicated chemical systems and their application to phenol-formaldehyde systems has been well documented . ... 

Methanol oxidation was carried out in a conventional flow apparatus at atmospheric pressure. The feed mixtures were prepared by injecting the liquid methanol into air flow with a Gilson 302 pump. The catalyst was diluted with inert carborundum (1 3 volume ratio) to avoid adverse thermal effects, and placed in a tubular pyrex reactor with a coaxially centred thermowell with thermocouple. The reactor outlet was kept at 403 K, to prevent condensation of liquid products and formaldehyde polymerization, and it was connected with multicolumn Shimadzu GC-8A gas chromatograph with thermal conductivity detector. The column system used (1.5m of Poropak N+1.5m of Poropak T+0.9m of Poropak R) could separate CO2, formaldehyde, dimethylether, water, methylformate, dimethoxymethane and formic acid. The last product was never detected. 

The second patent80 describes the conversion of ethylene into ethylene ozonide followed by the immediate decomposition of the latter into formaldehyde. The primary object in this process is to so regulate the reaction as to produce a large yield of formaldehyde or its polymerization product, paraformaldehyde, while reducing the formation of formic acid to a minimum. The procedure is similar to that which has been described in the case of the preceding patent and differs principally in the fact that no catalyst is employed. For example, ethylene, ozonized air and water vapor are introduced into a drum, tower, or other convenient form of apparatus which will facilitate an intimate mixture of the substances. The following reactions are supposed to occur ... 

It was reported that the reaction of starch with phenol in the presence of a Lewis acid such as AICI3 resulted in resins of controlled melt viscosity.252 Probably, the product results from the hydrolysis of starch to glucose with conbversion of the latter into 5-(hydroxymethyl)-2-furaldehyde, which subsequently condensed with phenol.253 The reaction of starch with phenol without any catalyst required temperatures between 200 and 260 °C, and the resultant resinous product was then hardened by condensation with formaldehyde.254 Mastication of either glycerol or phenol with starch and water was said not to involve alcoholysis, but instead results in the formation of polymeric products.255 Reactions with gossypol256,257 and propylene glycol258 that were performed in the presence of a basic catalyst were in fact polymerization reactions and not alcoholyses. 

Solution Polymeric products of formaldehyde, knovm for over 100 years, are quite unstable for commercial use, Thermal stability could be improved by acetylation of the hydroxyl end groups using acetic anhydride. 

Formaldehyde can be analyzed by several instrumental techniques, such as GC, colorimetry, polarography, and GC/MS. The GC method involves the passage of air through a solid sorbent tube containing 2-(benzylamino)ethanol on Chro-mosorb 102 or XAD-2. The derivative, 2-benzyloxazolidine, is desorbed with isooctane and injected into GC equipped with an FID (NIOSH 1984, Method 2502). Car-bowax 20M or a fused-silica capillary column is suitable. 2-Benzyloxazolidine peak is sometimes masked under the peaks, due to the derivatizing agent or its decomposition and/or polymeric products. The isooctane... 

Reaction rates are slower than for addition polymerization and lower molecular weight products are formed. Condensation polymers include polyesters, nylons, polycarbonates, formaldehyde polymers and epoxies. Compared with polymers created by addition polymerization, products of condensation reactions harden on heating (thermosetting), are brittle, poorly soluble in hydrocarbons and may be swollen but not dissolved by chlorinated liquids. More details of the synthesis processes for the condensation polymers most commonly found in heritage collections are presented next. 

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