Methylol phenol

The chemistry of melamines and phenoHcs is quite similar. In both cases formaldehyde [50-00-0] is added to the reactive sites on the patent ring to form methylol phenols (3) or methylol melamines (4) (see Phenolresins Aminoresins). There ate six reactive sites on the triazine ring of melamine [108-78-1] (1) so it is possible to form hexamethylolmelamine. However, the most common degree of methylolation is 1.5—2.0. The ortho and para positions of phenol ate active thus phenol can be trimethylolated (2). However, as with melamine, lower degrees of methylolation such as 1.2—2.5 ate... 

Zinc acetate catalyst produces essentially 100% o-methylol phenol (8) in the first step. The second step gives an approximately equal quantity of 2,2 -(5, 45%) and 2,4 -diphenyhnethylene (6, 45%) bridges, indicating Htde chelate-directing influence. In addition, a small quantity (10%) of methylene ether units (9) (diben2yl ether) is observed at moderate reaction temperature. 

Quinone dioximes, alkylphenol disulfides, and phenol—formaldehyde reaction products are used to cross-link halobutyl mbbers. In some cases, nonhalogenated butyl mbber can be cross-linked by these materials if there is some other source of halogen in the formulation. Alkylphenol disulfides are used in halobutyl innerliners for tires. Methylol phenol—formaldehyde resins are used for heat resistance in tire curing bladders. Bisphenols, accelerated by phosphonium salts, are used to cross-link fluorocarbon mbbers. 

The mechanism of the hardening proeesses has been investigated by Zinke in Austria, von Euler in Sweden and Hultzsch in Germany using blocked methylol phenols so that only small isolable products would be obtained. 

In general their work indicates that at temperatures below 160°C cross-linking occurs by phenol methylol-phenol methylol and phenol methylol-phenol condensations, viz Figure 23.13. 

A real co-condensation between phenol and urea can be performed by two ways (I) reaction of methylol phenols with urea [98-101] (2) acidic reaction of UFC (urea-formaldehyde concentrate) with phenol followed by an alkaline reaction [102,103]. 

Alkaline co-condensation to yield commercial resins and the products of reaction obtained thereof [93,94] as well as the kinetics of the co-condensation of mono methylol phenols and urea [104,105] have also been reported [17]. Model reactions in order to prove an urea-phenol-formaldehyde co-condensation (reaction of urea with methylolphenols) are described by Tomita and Hse [98,102, 106] and by Pizzi et al. [93,104] (Fig. 1). 

The first step in the hase-catalyzed reaction is an attack hy the phe-noxide ion on the carhonyl carhon of formaldehyde, giving a mixture of ortho- and para-suhstituted mono-methylolphenol plus di- and trisuhsti-tuted methylol phenols ... 

The F-test indicates the dependence of die dependent variables widi the independent variables, P level indicates the statistical significance of the correlafion(Table 4). The F-test results for the relation of the amount of ortho methylol phenols with F/P molar ratio and the reaction temperature were low, however, for the OH/P wt %, the F-test result was very significant, indicating a clear dependence of ortho methylol phenols on the OH/P wt %. It can also be seen that P level values for the relation between the amount of ortho methylol phenols and both F/P molar ratio and reaction temperature are above the set P value of 0.05, while for the OH/P wt%, the P value is under the set value. This data indicated that the relations of dependent variables ortho methylol phenols with independent variable OH/P wt% is statistically significant at the 0.05 significmitx level, while tiie relation of dependent variables ortho methylol phenols with F/P molar ratio and reaction temperature are not statistically significant. 

F/P molar ratio showed an increasing effect, while ruction temperature demonstrated a decreasing effect on mono-substitution of methylol group. Three independent variables demonstrated no statistically significant effect on di-substitution of methylol groups. Trisubstitution of methylol groups, para methylol phenols, o-p methylme brid, dirnCT formation, the amount of firee phenols, and the fraction of o-p Vp-p were dependent on all of the three indqrendent variables. 

Braze, M. 1986. Sensitizing capacity of 2-methylol phenol, 4-methylol phenol and 2,4,6-trimethylol phenol in the guinea pig. Contact Dermatitis 14 32-38. 

Condensation product of methylol phenol derivatives and polyethylenepolyamine... 

Polymerization under alkaline conditions, using about 1% sodium hydroxide catalyst based on the weight of the phenol, proceeds via a somewhat different mechanism. Methylol phenols, and oligomers consisting of 5 or 6 phenol units connected by methylene bridges, result in the so-called resole resin prepolymer (Eq. 21.33). 

Relatively little basic information has been published regarding the kinetics of phenol-formaldehyde intermediates, especially of phenols, methylol phenols, benzyl alcohol and benzylic ethers with isocyanates. Due to the fact that a typical resole contains both phenolic and benzylic hydroxyl groups, it was of interest to determine their reactivity toward isocyanates in the presence of various catalysts, as well as the effect of substitution on their reactivity. This investigation describes the kinetics of model phenols and model benzyl alcohols with phenyl isocyanate catalyzed with either a tertiary amine (dimethylcyclo-hexylamine, DMCHA) or an organotin catalyst, dibutyltin dilaurate (DBTDL) in either dioxane or dimethylformamide solution. 

Base-Catalyzed Reactions. When a base catalyst is used, raising the pH above 8, the first products formed are various hydroxybenzy 1 alcohols. When unsubstituted phenol is used, five different alcohols can be formed, since formaldehyde will react at the two ortho and the one para position to the phenolic hydroxyl. These alcohols, commonly referred to as methylol phenols, are found in varying relative amounts depending on the ratio of formaldehyde to phenol present and various reaction conditions such as time and temperature. 

Aldehydes can methylolate phenols with an acid as a catalyst and therefore function as latent electrophiles in the negative resist design based on condensation (Fig. 125) [150]. The methylolated phenolic resin is expected to dissolve more slowly in aqueous base than its precursor resin and therefore this process could be exploited in negative imaging. Furthermore, the methylolated phenol can undergo further condensation with phenol. If the phenol is polymeric, the second reaction results in crosslinking, lowering the dissolution rate even further. 

The lack of reaction between methylolated phenol and cellulose reported by Allan and Neogi seems to contradict the findings of Chow and coworkers. One possible explanation for this disparity could be the difference In available free formaldehyde In their systems. Allan s model phenolic adhesive would have the equivalent of only one mole of formaldehyde per mole of phenol and would not be expected to have significant quantities of free formaldehyde. The resins used by Chow and coworkers had about 2 moles of combined formaldehyde per mole of phenol. Such resins are able to release formaldehyde during cure idien condensation occurs between two methylol groups. This formaldehyde ml t then add at the aliphatic hydroxyls on cellulose or lignin resulting In condensation, as proposed by Chow, between the methylolated wood components and the phenolic resins. 

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