Epoxy cresol/phenol

Alkylated phenol derivatives are used as raw materials for the production of resins, novolaks (alcohol-soluble resins of the phenol—formaldehyde type), herbicides, insecticides, antioxidants, and other chemicals. The synthesis of 2,6-xylenol [576-26-1] h.a.s become commercially important since PPO resin, poly(2,6-dimethyl phenylene oxide), an engineering thermoplastic, was developed (114,115). The demand for (9-cresol and 2,6-xylenol (2,6-dimethylphenol) increased further in the 1980s along with the growing use of epoxy cresol novolak (ECN) in the electronics industries and poly(phenylene ether) resin in the automobile industries. The ECN is derived from o-cresol, and poly(phenylene ether) resin is derived from 2,6-xylenol. 

The epoxy cresol—novolak resins (2) are prepared by glycidylation of o-cresol—formaldehyde condensates in the same manner as the phenol—novolak resins. The o-cresol—formaldehyde condensates are prepared under acidic conditions with formaldehyde—o-cresol ratios of less than unity. 

The literature on basic- and acid-catalyzed alkylation of phenol and of its derivatives is wide [1,2], since this class of reactions finds industrial application for the synthesis of several intermediates 2-methylphenol as a monomer for the synthesis of epoxy cresol novolac resin 2,5-dimethylphenol as an intermediate for the synthesis of antiseptics, dyes and antioxidants 2,6-dimethylphenol used for the manufacture of polyphenylenoxide resins, and 2,3,6-trimethylphenol as a starting material for the synthesis of vitamin E. The nature of the products obtained in phenol methylation is affected by the surface characteristics of the catalyst, since catalysts having acid features address the electrophilic substitution in the ortho and para positions with respect to the hydroxy group (steric effects in confined environments may however affect the ortho/para-C-alkylation ratio), while with basic catalysts the ortho positions become the... 

The epoxy-cresol—novolaks resins are prepared by glyci-dylation of o-cresol-formaldehyde condensates in the same manner as phenol-novolak resins, o-cresol-formaldehyde condensates are prepared under acidic conditions with HCHO-o-cresol ratios of less than unity. The o-cresol novolacs of commercial significance possesses degrees of polymerization, n, of 1.7-4.4 and the epoxide functionality of the resultant glycidylated resins varies from 2.7 to 5.4. Softening points (Durrain s) of the products are 35-99°C [31]. 

All samples were prepared from a commercially available epoxy cresol novolac-phenol formaldehyde novolac-tertia-ry amine based molding compound. Pelletized preforms were heated to 85°C in a RF preheater prior to being transfer molded at 180°C/68 atm. for 90 sec. Molded samples were cooled in air to room temperature and stored in a desiccated environment until testing or subsequent thermal treatment. Post mold curing, PMC, was accomplished in a gravity oven at 175°C for a period of 4 hours. Samples without post mold curing are designated by NPMC. 

TYPICAL CLEAR CASTING DATA OF PHENOLIC-CURED XD-9053.00L COMPARED WITH EPOXY CRESOL NOVOLAC RESIN... 

Benzidine dihydrochloride 4,4 -Methylenebis (2-chloraniline) Phenolic resin hardener, steel Calcium cyanamide hardener, textiles Epoxy cresol novolac hardener, tissue Zinc PCA... 

The neat novolac resins are also the precursors in the manufacture of a range of (see Epoxide adhesives), such as epoxy phenol novolacs and epoxy cresol novolacs spoxy resins. 

Novolac epoxy resins, phenolic or cresol novolacs, are reacted with epichlorohydrin to produce these novolac epoxy resins which cure more rapidly than the epi-bis epoxies and have higher exotherms. These cured novolacs have higher heat-deflection temperatures than the epi-bis resins as shown in Table 2.8. The novolacs also have excellent resistance to solvents and chemicals when compared with that of an epi-bis resin as seen in Table 2.9. 

Another class of epoxy resins is the novolacs, particularly the epoxy cresols and the epoxy phenol novolacs. These are produced by reacting a novolac resin, usually formed by the reaction of o-aesol or phenol and formaldehyde with epichlorohydrin. These highly functional materials are particularly recommended for transfer molding powders, electrical laminates, and parts in which superior thermal properties, high resistance to solvents and chemicals, and high reactivity with hardeners are needed. 

Epoxy NovolaC Resins. Epoxy novolacs are multifunctional epoxies based on phenolic formaldehyde novolacs. Both epoxy phenol novolac resins (EPN) and epoxy cresol novolac resins (ECN) have attained commercial importance (53). The former is made by epoxidation of the phenol-formaldehyde condensates (novolacs) obtained from acid-catalyzed condensation of phenol and formaldehyde (see Phenolic Resins). This produces random ortho- and para-methylene bridges. 

Others include brominated bisphenol A resins which impart fire resistance, epoxy phenol novolac (EPN) resins, bisphenol F epoxy (DGEBF) resins, epoxy cresol novolac (ECN) resins, cycloaliphatic epoxy resins, and tetraglycidyl-4,4 -diaminodiphenylmethane (TGDDM). 

Extensive development of both EPM (epoxy phenol novolac) and ECM (epoxy cresol novolac) resins has occurred to improve the quality of the resins by a reduction of ionic and reactive chlorohydrin... 

It is clear from the above discussions that in different mechanisms for the reaction of epoxy with phenol have been reported in the research literature. Some explain the role of the tertiary amine or phosphine as being that of a catalyst. Others deem its role to be part of a larger activated catalytic complex. Still others explain its role as being that of an ionic reaction initiator. Next, these proposed mechanisms will be evaluated with r ards to their abihty to explain the experimental observations for an epojQT cresol novolac-phenohc novolac resin. 

Multifunctional epoxy resins such as aromatic glycidyl ether resins and aromatic glycidyl amine resins are commercially available. Commercially important epoxy phenol Novolac resins and epoxy cresol Novolac resins are prepared from excess epichlohydrin and phenol-formaldehyde or o-cresol-formaldehyde resins. The high functionality of these Novolac resins increases crosslink density and improves thermal stability and chemical resistance ... 

Epoxy novolac resins are produced by glycidation of the low-molecular-weight reaction products of phenol (or cresol) with formaldehyde. Highly cross-linked systems are formed that have superior performance at elevated temperatures. 

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). 

Biernath et al. concluded that phenolic novolac and epoxidized cresol novolac cure reactions using triphenylphosphine as the catalyst had a short initiation period wherein the concentration of phenolate ion increased, followed by a (steady-state) propagation regime where the number of reactive phenolate species was constant.85 The epoxy ring opening was reportedly first order in the steady-state regime. 

The epoxy novolac resins are synthesized by reaction of phenolic or cresol novolacs with epichlorohydrin in the same fashion as the bisphenol A resins. The number of epoxy groups per molecule is dependent on the number of hydroxyls in the phenol novolac molecule and to the extent to which they are reacted. Complete epoxidation can be accomplished, but this will lead to steric factors, which could limit the useful size of the cured polymer. Thus, selective epoxidation is often practiced.9... 

Epoxy novolac resins are polyglycidyl ethers of a novolac resin. They are prepared by reacting epichlorohydrin with a novolac resin (see Chap. 2). The most common epoxy novolacs are based on medium-MW molecules with phenol and o-cresol novolacs. They generally have significantly different properties from DGEB A epoxies because of the presence of the phenolic structure. 

These resins (Resole or Novolac) are used as curing agents or hardeners for epoxy molding compounds for electronics applications such as computer components. 0-cresol-formaldehyde resins have heen also used to modify phenol-formaldehyde resins, and in laminates. 

Antioxidants, particularly, BHT are produced from phenol by only one unit in Russia, otherwise, in all other plants in the world p-cresol (or even m-p-cresol) is the critical feedstock for production of BHT. o-Cresol-based epoxy resins, particularly in Japan, have proved to be very attractive and is partly replacing epoxy resins made from phenol via bisphenol-... 

---