P-Cresol-formaldehyde

A mixture of three isomeric cresols is used in a commercially available cresol-formaldehyde Novolak resin. This mixed Novolak resin, Varcum resin (12), provides adequate properties as a host resin for near-UV- and mid-UV-photoresist applications. Gipstein and his co-workers prepared pure cresol-formaldehyde Novolak resin from each isomeric cresol and compared their spectroscopic and resist characteristics (13). Their data on the UV-absorption spectra of each cresol-formaldehyde Novolak resin together with the commercially available Varcum resin are as follows the absorbances of 0.2 jim thick Novolak films at 250 nm are 0.165(Varcum), 0.096(o-cresol), 0.092(m-cresol), and 0.055(p-cresol). The so-called "window" in the UV absorption at around 250 nm is a maximum with the p-cresol-formaldehyde Novolak resin, while the other isomeric cresol and formaldehyde Novolak resins yielded similar UV absorptions at this wavelength. The smallest UV absorption at 254 nm is an advantage for the p-cresol-formaldehyde Novolak when the resin is used for a deep UV photoresist with a suitable photoactive compound (14). 

This paper illustrates its application to problems encountered in studies on polymer modification reactions, polymer epimerization reactions, p-cresol-formaldehyde condensation reactions, and monomer-promoted polyaddition reactions. A 23-statement CSMP program was written, for example, to duplicate the predictor-corrector program of Bauer for simulating irreversible polymer modification reactions. 

Novolac Preparation Novolac resins were prepared by an acid catalyzed condensation of m- and p-cresols with formaldehyde. A three necked flask with a distillation reflux condenser, thermometer and mechanical stirrer was charged with m- and p-cresols, formaldehyde aqueous solution, and cone, hydrochloric acid as a catalyst. The flask was immersed in an oil bath and heated to 90 C and kept for 2 hours while undergoing stirring. After the flask was cooled to room temperature on standing, the supernatant layer of the contents was removed by decantation. Then the volatile components were eliminated by distillation under a nitrogen gas flow and slow heating to 175°C. The molten content was poured into a stainless steel tray to cool. 

Addition of p-cresol formaldehyde (PCF) into phenolic/NBR blends resulted in rednction in the domain size of the dispersed phase and improvement in mechanical properties [244]. PCF resin has an intermediate polarity compared with NBR and resole and can react faster with NBR. Therefore, PCF molecules are likely to be concentrated at the phenolic/NBR interface and act as an external compatibilising agents [245]. Thus compatibility and chemical bonding between NBR and phenolic resin is improved, leading to the enhancement in properties. The other materials used as toughening agents of phenolic resin include elastomers such as natural rubber and nitrile rubber [246, 247], reactive liquid polymers [248] and thermoplastics such as polysulfone, polyamide, polyethylene oxide [249, 250]. 

Table 145. hRf-values of some p-cresol-formaldehyde condensation products (see [30] for others) on silica gel layers, using solvents I Benzene-methanol-acetic oaM (95 2,5 -f- 2,5) II Benzene-methanol (75 + 25) III Chloroform-methanol (96 -j- 4). 

In addition to the above possible mechanisms the possibility of reaction at w-positions should not be excluded. For example, it has been shown by Koebner that o- and p-cresols, ostensibly difunctional, can, under certain conditions, react with formaldehyde to give insoluble and infusible resins. Furthermore, Megson has shown that 2,4,6-trimethylphenol, in which the two ortho- and the one para-positions are blocked, can condense with formaldehyde under strongly acidic conditions. It is of interest to note that Redfam produced an infusible resin from 3,4,5,-trimethylphenol under alkaline conditions. Here the two m- and the p-positions were blocked and this experimental observation provides supplementary evidence that additional functionalities are developed during reaction, for example in the formation of quinone methides. 

Figure 44.5. Conversion of phenol ( ), molar selectivity to anisole (X), o-cresol (O), p-cresol (A), 2,6-xylenol (O), salicylaldehyde ( ) and polyalkylated phenols ( ) as functions of temperature. Catalyst H-mordenite. Feed composition N2 89.3%, formaldehyde 1.7%, phenol 0.46%, methanol 0.03% and water 8.5%.

Another useful class of intermediates in this series was found to be the 2-hydroxy-3,5-dialkylbenzyl 2-benzothiazolyl sulfides, some of which are described in Table III. John Bill of our laboratories had previously found that 2-terf-butyl-p-cresol will react with formaldehyde and mer-captobenzothiazole under acid conditions to produce 2-hydroxy-3-ferf-butyl-5-methylbenzyl 2-benzothiazolyl sulfide, XX, in 70% yield. 

Toluene o-Cresol m-Cresol p-Cresol m-Nitrotoluene o-Nitrotoluene p-Nitrotoluene Benzaldehyde 2-Methyl-p-benzoquinone Benzyl alcohol Benzyl nitrate Glyoxal Methyl glyoxal Methylbutenedial Hydroxymethylbutenedial Oxoheptadienal Methylhydroperoxide Formaldehyde Hexadienyl Hydroxyoxoheptadienyl Maleic anhydride... 

The structures of the lignins are amenable to conversion to several classes of substituted phenols by thermochemical and thermal degradation methods. The displacement of pyroligneous tars by coal tars eliminated much of the demand that existed for the lignin-based products. Creosote oil or cresylic acid, a mixture of o-, m-, and p-cresols, is now manufactured mainly from coal tars, while only small amounts of cresols are made from wood tars. The use of wood tars and other biomass-derived tars as substitutes for a major portion of the phenol and formaldehyde in phenol-formaldehyde resins could reverse this trend (Himmelblau, 1995). The key to this process seems to be that the... 

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). 

Presumably the linking group is >NCH—N<. Bisamides of l-(amino-phenyl)-2-pyrazolin-5-ones and of 3-amino-2-pyrazolin-5-ones have been used. l-(3-Aminophenyl)-3-methyl-2-pyrazolin-5-one reacts with many aldehydes and ketones to form polymers.964 Probably condensation occurs at C-4 and the amino group. The product of reaction of p-cresol with formaldehyde has been found to react with 1-(4-hydroxy -phenyl)-3-methyl-2-pyTazolin-5-one to give a polymer that must have the aromatic and pyrazolinone rings connected by ether linkages.1269... 

In the breakdown by chemical composition, phenol-formaldehyde protective coating resins are broken out from 1941 through 1946. Cresol-formaldehyde (cresylic acid-formaldehyde) protective coating resins are broken out for 1941 through 1943. p-tert-Amy -phenol-formaldehyde is shown separately for 1945 and 1946. Phenol and cresol-aldehyde resins are shown in 1941 and 1952. Mixed phenolic resins are shown for protective coatings in 1945 and 1946 (71). 

Phenol-formaldehyde and allied resins VI Rational synthesis of a cyclic tetranuclear p-cresol novolak, B. T. Hayes and R. F. Hunter, J. Appl. Chem., 1958, 8, 743. 

The goal is to prepare phenolic resins without the use of formaldehyde (a carcinogen). Yields can be as high as 90-95%. The products from phenol and p-cresol are only... 

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