Phenol-formaldehyde oligomers

Synthesis of phenol-formaldehyde oligomers uses as the main raw materials phenol and formic aldehyde. Both are used in the form of aqueous solutions of 90% and 40-45% concentration, respectively [1], Since formaldehyde contains small amounts of formic acid, the condensation process can take place in the absence of catalysts, so that phenol-formaldehyde oligomers can be obtained. The reaction rate is, however, quite low when the process takes place at atmospheric pressure and a temperature around 100°C. The use of acid or basic catalysts is compulsory in industry to produce phenol-formaldehyde oligomers of desired characteristics. Novolac type oligomers are obtained in acid catalysis in basic catalysis, resol type oligomers are produced. 

According to reaction (1), mono-, di-, and trihydroxymethylene derivatives of phenol can be formed. Both in acid and in alkaline media, the first stage of the process should be the formation of a monohydroxymethylene derivative of phenol. Subsequent development of the process is determined by the value of the constants ki and fej. If fei 2, the process leads to the accumulation of hydroxymethylene derivatives of low molecular weight. If fei 2, monohydroxymethylene derivatives of phenol react with each other so that linear oligomers are obtained. 

To obtain novolac type oligomers, the most active catalyst is hydrochloric acid. Its concentration is determined by two factors formaldehyde acidity and the pH value of the reaction medium (1.8-2.2). As a rule, for HCl a concentration of 0.1 to 0.3% is used vs. the phenol concentration introduced. 

Novolac oligomers obtained in the presence of HCl develop with violent heat of reaction. This is why the introduction of HCl (37% solution) is performed step by step. In the acid catalysis achieved with sufuric acid, the reaction product is brown-colored, and ultimately H2SO4 neutralization with Ba(OH)2 or Ca(OH)2 is required. 

Because of corrosion, the synthesis of novolac type oligomers catalyzed by mineral acids has been abandoned. To this, the remark may be added that in the situation in which HCl and CH2O concentration in the gaseous phase exceeds 

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Various ionization methods were used to bombard phenol-formaldehyde oligomers in mass spectroscopic analysis. The molecular weights of resole resins were calculated using field desorption mass spectroscopy of acetyl-derivatized samples.74 Phenol acetylation was used to enable quantitative characterization of all molecular fractions by increasing the molecular weights in increments of 42. 

Phenol-formaldehyde oligomer Poly(methyl methacrylate)... 

Microspheres based on phenol formaldehyde oligomers (PhFO s) are brown non-cohesive powders with particle sizes of 10—300 pm, apparent densities of 100 to 150 kg/m3, and sinkages of less than 5—10 mass% u,24 26). 

Oligomeric allene derivatives were also prepared using phenolic-formaldehyde oligomers illustrated in Eq. 1 ... 

This chapter is concerned with green reactions, products and methodological advances facilitating them. To those ends, our work has attempted to simplify processes by combining as many tasks as possible into unit operations. Aspects include selection of media, reactants, catalysts, conditions and product isolation. Examples are presented along with details of some specific classes of relatively complex molecules that may be prepared. These include novel macro-cycles, ligands and phenol/formaldehyde oligomers. 

Figure 6.1 Representative structures of products accessible using the strategies outlined below include bis-arylidinealkenones (3), 2,6-dibenzylphenols (4), dienone (5 and 7) and Horning-crown (6 and 8) macrocycles, rods (9) and flexible phenol/formaldehyde oligomers (10).

Isoaromatization of rods containing cyclohexyl residues led to the preparation of phenol/formaldehyde oligomers, such as examples 34 and 35, thus illustrating the possibilities of preparing designer phenol/formaldehyde oligomers for modulating the properties of such resins. 

Figure 6.9 Rod-like molecules 30-32 and phenol/formaldehyde oligomers 34 and 35.

The extended rod structures and flexible phenol/formaldehyde oligomers offer interesting opportunities in the development of nonlinear optical (NLO) materials and Bakelite modifiers, respectively. 

Composites Prepared from Cycloaliphatic and Aliphatic-Cydoaliphatic Epoxy Compounds Crosslinked with Phenol-Formaldehyde Oligomers... 

In this chapter, we will discus the synthesis and investigation of some properties of copolymers produced in result of copolymerization of epoxy-silicon oligomers and novolac phenol-formaldehyde oligomers have been carried out. 

Epoxy group functionalized polyphenylsilsesquioxane oligomers were used for modification of phenol-formaldehyde oligomer (novolac resin -SF-0112) for increasing their flexibility, their hydrophobic surface properties, thermal stability and flame-retardant properties. Novolac resin - SF-0112 contains a little amount of free phenols (0.9%) compared with other phenol-formaldehyde oligomers. 

Pol)merization reaction of phenol-formaldehyde oligomer (novolac resin - SF-0112) with tetraepoxypolyphenylsilsesquioxanes was carried out in melt condition at 125 5°C temperature at various ratios of initial compounds, without catalyst. The samples were tested on contain of epoxy groups during the reaction. It was shown that during synthesis of block-copolymers the reaction rate decreases, which may be explained by presence of free phenols in used phenol-formaldehyde oligomer. In accor-... 

SCHEME 11. MODIFICATION REACTION OF NOVOLAC PHENOL-FORMALDEHYDE OLIGOMER BY EPOXY GROUP CONTAINING POLYPHENYLSILSESQUIOXANE OLIGOMER. N=1-2, WHERE, N=1 (XVIII) 2 (XIX). 

FIGURE 16 The dependence of amount of epoxy groups on time in reaction mixture with different ratio of phenol-formaldehyde oligomer to tetraepoxypolyphenylsilsesquioxane 1 -60 40 2-40 60 3-30 70. 

Novolac-epoxy netwoiks can be modified with reactive epoxy fimctional polysiloxane oligomers. In accordance with FTIR spectra of the reaction products obtained at various temperatures with an increase of amount of phenol-formaldehyde oligomer in reaction mixture the concentration of epoxy groups decreases rapidly. The composite materials on the basis of organo-inorganic block-copolymers has been obtained and studied. 

Table 2 Melting Points of the Phenol-Formaldehyde Oligomers with General Formula A...

In polymer synthesis, calixarenes - cyclic phenol-formaldehyde oligomers - are rarely studied and reported. There are two main applications of calixarenes in polymer synthesis use of metal calrxarene complexes as catalysts for polymerization and star-shaped polymers with a calixarene core. 

Figure 3.9. Phase state diagrams of phenol-formaldehyde oligomer blend with butadiene - nitrile rubbers. SKN-18 (1), SKN-26 (2), SKN-40 (3). 91 is the volume fraction of oligomer.

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