Phenol-formaldehyde nitrogen

Technological advances continue to be made, several recent patents describe advanced phenol—formaldehyde—furfuryl alcohohol biader systems (68—70). These systems are free of nitrogen compounds that can be detrimental to metal iategrity. Systems with extended bench life have also been developed (71). 

Compounds with triple bonds, i.e. acetylenic compounds, continue to receive attention. Patents have been filed for mixtures of propargyl alcohol with, for example, cellosolve + a phenol formaldehyde resin + tar bases heterocyclic nitrogen compounds + acetylenic + dialkylthiourea or a quaternary + antimony oxide . 

A Friedel-Crafts-type reaction of phenols under basic conditions is also possible. Aqueous alkaline phenol-aldehyde condensation is the reaction for generating phenol-formaldehyde resin.34 The condensation of phenol with glyoxylic acid in alkaline solution by using aqueous glyoxylic acid generates 4-hydroxyphenylacetic acid. The use of tetraalkylammonium hydroxide instead of sodium hydroxide increases the para-selectivity of the condensation.35 Base-catalyzed formation of benzo[b]furano[60]- and -[70]fullerenes occurred via the reaction of C60CI6 with phenol in the presence of aqueous KOH and under nitrogen.36... 

Mesoporous melamine-formaldehyde and phenolic-formaldehyde resins were synthesized in the process of polymerization in the presence of fumed silica as an inorganic template. The surface and structural characteristics of the obtained sorbents were investigated using XPS technique and sorption from gas phase. The parameters characterizing porous structure of the synthesized resins in a dry state were determined from nitrogen adsorption/desorption isotherms. The sorption processes of benzene and water vapor accompanied by simultaneous swelling of both polymers were also studied. 

Data of low-temperature nitrogen adsorption were used to evaluate the parameters characterizing the pore structure of the obtained polymeric materials in dry state. The BET specific surface area, Sbet, and the total pore volume, V, were estimated by applying the standard methods Sbet from the linear BET plots and F/ from adsorption at relative pressure p/po=0.975) [7]. The mesopore structure was characterized by the distribution function of mesopore volume calculated by the Barret-Joyner-Halenda (BJH) method [27]. In Table 2 the values of these parameters are given for both synthesized polymers. The melamine-formaldehyde resin MEA has a more developed pore structure (5 B 7=220mVg, F,=0.45cm /g) and narrower mesopores (D=7.3nm) in comparison to the phenolic-formaldehyde polymer PHD. 

The synthesis of phenolic-formaldehyde and melamine-formaldehyde resins in the presence of fumed silica allows obtaining porous organic materials with a differentiated porous structure and surface properties. The pore characteristics of the studied resins in dry state were determined from nitrogen adsorption isotherms. The differences in surface character of the synthesized polymers were estimated satisfactorily by XPS spectra showing the presence of various functional groups. The adsorption/desorption mechanism of water and benzene on the investigated porous polymers was different due to differentiated hydrophobicity of the bulk material. 

Example 4. Polyurethane formation, in which the alcohol adds across the carbon nitrogen double bond of the isocyanate function (0 = C = N-R) to form the urethane (-0-C0-NH-) link without loss of a small molecule, represents an exception to this general recognition feature of polycondensations. Bakelite is one of several possible products from phenol-formaldehyde resins, and these may or may not involve loss of a small molecule. This more complicated process will be discussed in further detail later. 

We will not discuss here models for pores in carbons, as this topic is treated in Chapter 5, and elsewhere in specialist [15] or general reviews [106, 107]. For similar reasons, we will not discuss porosity control [44, 108] in detail. However, porous carbons prepared by the template technique, especially the ordered ones, deserve special attention. Ordered mesoporous carbons have been known to scientists since 1989 when two Korean groups independendy reported their synthesis using mesoporous silicas as templates [109, 110]. Further achievements have been described in more recent reports [111, 112]. One might have expected that the nanotexture of these materials would merely reflect the nature of the precursor used, namely phenol-formaldehyde [109] or sucrose [110] in the two first ordered mesoporous carbon syntheses (as is well known, these two precursors would have yielded randomly oriented, isotropic carbon had they been pyrolyzed/activated under more conventional conditions). However, the mesopore walls in some ordered mesoporous carbons exhibited a graphite-like, polyaromatic character [113, 114], as described in Chapter 18. This information was obtained by nitrogen adsorption at low relative pressures, as in classical... 

Figure 5. Phenol-formaldehyde particleboard elution by nitrogen at different relative humidities (RH). (0.5 NCM. P as in...

Figure 10. Formaldehyde loss ratios at 20 percent relative humidity for various materials. (Formaldehyde removed from a material divided by that removed from urea-formaldehyde particleboard. Board elution by nitrogen. Resin liberation by weighing bottle test. PF = phenol-formaldehyde) (ML85 5437)...

A simple way to produce polymers with specific nitrogen functions in controlled concentration is to prepare phenol-formaldehyde resins in which part of the phenol is substituted by aniline (for amine-type nitrogen) or... 

Table 7.1 Development of Nitrogen Content of Activated Chars from Phenol-Formaldehyde Resin on Heat TVeatment (5 Hours) Under N2 and Ar ...

Figure 7.13 demonstrates the accelerating effect of increasing nitrogen content on the activity in aging of activated carbons from phenol-formaldehyde resin, in which part of the phenol was substituted by aniline [164]. The surface area was from 700 to 840 m /g. The oxidation rate increased almost linearly with the nitrogen content. Conversion to carbonate proceeds much more slowly at room temperature reaction times of one to two months were necessary to obtain well-measurable results [163]. 

Figure 7.13 Carbonate formation in the reaction with O2 of nitrogen-containing activated carbons prepared from phenol-formaldehyde resin with the addition of aniline. (Adapted from ref. 164.)...

This autoxidation property of carbons leads to a continuous loss of catalyst. When spherical carbon particles of 30 to 100 p,m were used in the oxidation with air of aqueous cyclohexanone solutions at 393 K in a trickle-bed reactor, a weak loss of carbon was observed after four weeks, and the originally smooth particles appeared rough and porous in scanning electron microscopy (SEM) [165]. The catalysts used with a nitrogen content of < 1% had been prepared from nitrogen-containing phenol-formaldehyde resin [166]. In this reaction cyclohexanone is oxidized to adipic acid and other dicarboxylic acids. 2-Hydroxycyclohexanone seems to be an intermediate. A carbon loss of several percent was also reported for other wet-air oxidation reactions of pollutants, mainly of phenol [167-169]. 

BSH is used for foaming rubbers, polystyrene, epoxy resins, polyamides, PVC, polyesters, phenol-formaldehyde resins, and polyolefins. However, the thermal decomposition of BSH yields not only nitrogen but also a nontoxic residue (disulfide and thiosulfone) which may degrade to give thiophenol and thus an unpleasant odor to the foams. 

A novel intumescent flame-retardant (IFR) system composed of a phosphorous-nitrogen (PSPTR)-containing spiro triazine structure and phenol formaldehyde resin (PF) was investigated by Hu et al. (Hu et al. 2012). 

The number of nitrogens in the chain can vary from two on up. In many cases the nitrogen-carbon bond is an integral part of the polymer network. There are more than two carbons between nitrogens in some cases, and the carbons may carry other substitutions. The actual ionogenic functionality is a mixture of primary, secondary and tertiary amines. Polyamine resins made by condensing phenol, formaldehyde and polyamine were among the first commercial resins. Other methods of manufacture include the reaction of a polyamine with a chloromethylated styrene-divinyl-benzene copolymer, and condensation of epichlorhydrin with ammonia or polyamines. 

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