Alkaline phenolic resin

Alkaline phenolic resin, ester hardened. The binder is a low viscosity, highly alkaline phenolic resole resin (1.2 to 1.7%). The hardener is a liquid organic ester (18 to 25%). Sand is mixed with hardener and resin, usually in a continuous mixer. The speed of setting is controlled by the type of ester used. Low sand temperature slows the cure rate, but special hardeners are available for cold and warm sand. In 24 h compression strength can reach 4000 kPa (600 psi). 

Ester-cured alkaline phenolic system. The resin is an alkaline phenolic resin (essentially the same as the self-hardening resins of this type). Sand is mixed with the resin and blown or manually packed into a core box. A vaporized ester, methyl formate, is passed through the sand, hardening the binder. The total resin and peroxide addition is 1.5%. Compression strengths of 5000 kPa (700 psi) are possible. 

Reaction of one mole of acetaldehyde and excess phenol in the presence of a mineral acid catalyst gives l,l-bis(p-hydroxyphenyl)ethane [2081-08-5], acid catalysts, acetaldehyde, and three moles or less of phenol yield soluble resins. Hardenable resins are difficult to produce by alkaline condensation of acetaldehyde and phenol because the acetaldehyde tends to undergo aldol condensation and self-resinification (see Phenolic resins). 

Adolph Baeyer is credited with the first recognition of the general nature of the reaction between phenols and aldehydes in 1872 ([2,5-7] [18], Table 5.1). He reported formation of colorless resins when acidic solutions of pyrogallic acid or resorcinol were mixed with oil of bitter almonds, which consists primarily benzaldehyde. Baeyer also saw resin formation with acidic and basic solutions of phenol and acetaldehyde or chloral. Michael and Comey furthered Baeyer s work with additional studies on the behavior of benzaldehyde and phenols [2,19]. They studied a variety of acidic and basic catalysts and noted that reaction vigor followed the acid or base strength of the catalyst. Michael et al. also reported rapid oxidation and darkening of phenolic resins when catalyzed by alkaline materials. 

Usually alkaline NaOH is used as catalyst, in an amount up to one mole per mole phenol (molar ratio NaOH/P), which corresponds to approx. 10 mass% alkali in the liquid resin. The pH of a phenolic resin is in the range of 10-13. The biggest part of the alkali is free NaOH, a smaller part is present as sodium phenate. The alkali is necessary to keep the resin water-soluble via the... 

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... 

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Polymers with hydroxyl groups undergo typical reactions of alcohols. Those with aromatic hydroxyl groups, such as phenolic resins, are attacked by aqueous alkaline solutions. 

From this result on MRS, we expected that a combination of phenolic-resin-based resist and aqueous alkaline developer would lead to etching-type dissolution and non-swelling resist patterns. In this paper, we report on a new non-swelling negative electron beam resist consisting of an epoxy novolac, azide compound and phenolic resin matrix (EAP) and discuss the radiation chemistry of this resist. 

In general, a high-molecular-weight phenolic resin is less alkaline-soluble than a low-molecular-weight one. Therefore, these high molecular weight poly(p-vinyl phenol) components may contribute to the decrease in solubility. Furthermore, we assume that the etching type dissolution of these resists is non-fractional, as was previously shown in the case of poly (methyl methacrylate-co-acrylonitrile) (15). 

Copolymers of furfural with phenol or phenol-formaldehyde polymers have been available commercially for many years. Since the acid-catalyzed reaction of furfural and phenol has been difficult to control, most industrial applications involve the use of alkaline catalysts. Furfural-phenol resins are used for their alkali resistance, enhanced thermal stability, and good electrical properties compared to phenol-formaldehyde resins. 

Novolac- or phenolic resin-based resists usually show no pattern deformation induced by swelling during development in aqueous alkaline solution. Examples of such resists are naphtho-quinonediazide/novolac positive photoresists, novolac-based positive electron-beam resist (NPR) (1), and azide/phenolic negative deep-UV resist (MRS) (2). Iwayanagi et al.(2) reported that the development of MRS proceeds in the same manner as the etching process. This resist, consisting of a deep-UV sensitive azide and phenolic resis matrix, is also sensitive to electron-beams. This paper deals with the development mechanism of non-swelling MRS and its electron-beam exposure characteristics. 

A novel, nonswelling DUV resist was developed by Iwayanagi et al. (77). This resist, known as MRS (micro resist for shorter wavelengths), consists of poly(p-vinylphenol) (structure 3.11), an alkaline-soluble phenolic resin, and an azide (structure 3.10). 

Phenolic Resin Adhesives. PF resin adhesives are low molecular weight prepolymers formed from phenol and formaldehyde, and are of the thermosetting type. The polymerization is controlled by the acid or alkaline conditions, i.e., pH, at which it is conducted. Another important reaction variable is the molar ratio of phenol to formaldehyde. By varying the time and temperature of reaction, and by choosing catalysts and phenols of varying reactivity, a wide variety of adhesives can be prepared for many applications and conditions. 

Resoles. Resoles are phenolic resins produced under alkaline conditions with a molar excess of formaldehyde, HCHO, over phenol in the reaction mixture. The initial reaction is the substitution of phenol with methylol (-CH2OH) groups, as shown in Figure 1, both at the ortho (I) and para (II) positions. Furthermore, because more than 1 mol of formaldehyde is used for each mole of phenol, products carrying two or three methylol groups (HI, IV) are also formed. The ortho para substitution ratio depends on the type of catalyst and pH, and decreases from 1.1 at a pH of 8.7 to 0.38 at a... 

The grafted polymer is soluble in the alkaline ph-12 developer. The unexposed phenolic resin protected by the insoluble napthoquinone diazide is unaffected by the developer. Since the polymers are photosensitive to 5500A , they could eventually be useful spinoffs as photodegradable polymers soluble in alkaline soils. 

Thermosetting phenolic resins include a number of polymers, the most common being obtained from the condensation of phenol with formaldehyde. The OH group on the benzene ring increases the reactivity in the o- and p- positions leading to three reactive centers for the phenolic component, while formaldehyde acts as having two active centers that can lead to a fully crosslinked polymer. The process may take place in neutral or alkaline conditions when in the first stage of the reaction, compounds known as methylol derivatives are formed. The condensation of phenol with formaldehyde occurs randomly at ortho- or para- position of the phenol, as shown below ... 

Another reason for predicting low emissions is that the small amount of residual formaldehyde that might be present in the prepared resin is diminished even farther by reactions which occur when the resin cures. Phenolic resins are cured under heat and pressure in a hot-press, usually under highly alkaline conditions. Curing temperatures are usually in the range of 130-220 C. Under these conditions, unreacted formaldehyde continues to react with phenol to form larger phenol formaldehyde polymers. Also, some formaldehyde reacts with various chemical constituents in the wood. Moreover, some formaldehyde is probably converted to methyl alcohol and formic acid by way of the Cannizzaro reaction (J ). ... 

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