Alkyl phenol resins

A wide range of products, including every class and type of surfactant, has been found to exhibit demulsification properties. The most commonly used products in lubricant formulations contain anionic surfactants such as alkyl-naphthalene sulphonates. Nonionic alkoxylated alkyl-phenol resins and block copolymers of ethylene oxide and propylene oxide are also used. 

Addition of 2 to 5 phr of alkyl-phenol resins improve tackiness of EPDM stocks. In blends with other synthetic rubbers such as SBR, the co-curability is an important factor while designing the overall curing system while compounding. The important factors to be considered here is to synchronise the curing speed between two polymers, using studies in oscillating disk rheometer charts. However, blends with styrene-butadiene rubber do not have as much acid resistance as 100% EPDM. 

Alkyl phenolic resin n. Phenol-formaldehyde resin in which the phenol used has an alkyl group in the para position. In resins used in coatings, the most common are the tertiary butyl and tertiary amyl phenols. 

The reactions of alkylphenols (containing substituents having at least three carbon atoms) with formaldehyde afford resins known as alkyl-phenolic resins [35]. Examples of suitable phenols include / /-/-butylphenol, octylphenol, and phenylphenol. 

Standard and modified phenolic resins, alkyl phenol resins, etherified phenolic resins, and phenol-terpene resins also are used as primers and resin components in other types of adhesives, for example, in contact cements, pressure-sensitive adhesives, rubber-to-metal bonding agents, and similar adhesive systems. 

The spotting tack and/or the heat resistance of elastomeric polyurethane adhesives may he extended by adding resins (alkyl phenolic, epoxide, terpene phenolic, coumarone) or polymers (low crystallizing polyurethane, acrylic, nitrile ruhher, chlorinated ruhher, acetyl cellulose) (Penczek and Nachtkamp 1987) with low miscihility with the polyurethane. To improve adhesion together with heat resistance, reactive alkyl phenolic resins, chlorinated rubber, or other chlorine-containing polymers can be added. 

I ovolac Synthesis and Properties. Novolac resins used in DNQ-based photoresists are the most complex, the best-studied, the most highly engineered, and the most widely used polymers in microlithography. Novolacs are condensation products of phenoHc monomers (typically cresols or other alkylated phenols) and formaldehyde, formed under acid catalysis. Figure 13 shows the polymerization chemistry and polymer stmcture formed in the step growth polymerization (31) of novolac resins. 

Substituted Phenols. Phenol itself is used in the largest volume, but substituted phenols are used for specialty resins (Table 2). Substituted phenols are typically alkylated phenols made from phenol and a corresponding a-olefin with acid catalysts (13). Acidic catalysis is frequendy in the form of an ion-exchange resin (lER) and the reaction proceeds preferentially in the para position. For example, in the production of /-butylphenol using isobutylene, the product is >95% para-substituted. The incorporation of alkyl phenols into the resin reduces reactivity, hardness, cross-link density, and color formation, but increases solubiHty in nonpolar solvents, dexibiHty, and compatibiHty with natural oils. 

The in situ process is simpler because it requires less material handling (35) however, this process has been used only for resole resins. When phenol is used, the reaction system is initially one-phase alkylated phenols and bisphenol A present special problems. As the reaction with formaldehyde progresses at 80—100°C, the resin becomes water-insoluble and phase separation takes place. Catalysts such as hexa produce an early phase separation, whereas NaOH-based resins retain water solubiUty to a higher molecular weight. If the reaction medium contains a protective coUoid at phase separation, a resin-in-water dispersion forms. Alternatively, the protective coUoid can be added later in the reaction sequence, in which case the reaction mass may temporarily be a water-in-resin dispersion. The protective coUoid serves to assist particle formation and stabUizes the final particles against coalescence. Some examples of protective coUoids are poly(vinyl alcohol), gum arabic, and hydroxyethjlceUulose. 

The resins can be a novolak—hexa or a resole—novolak blend. In some appHcations Hquid resoles are used. Addition of alkylated phenol, oil, or cashew nutsheU Hquid (CNSL) reduces hardness and increases abrasion resistance. Modification by mbber improves the coefficient of friction and reduces brake fading. 

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

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. 

Reactions with Aldehydes and Ketones. An important use for alkylphenols is ia phenol—formaldehyde resias. These resias are classified as resoles or aovolaks (see Phenolic resins). Resoles are produced whea oae or more moles of formaldehyde react with oae mole of pheaol uader basic catalysis. These resias are thermosets. Novolaks are thermoplastic resias formed whea an excess of phenol reacts with formaldehyde under acidic conditions. The acid protonates formaldehyde to generate the alkylating electrophile (17). 

Tackifiers. Phenolic resins are added to increase strength, oils resistance and resiliency of NBR adhesives. On the other hand, tack and adhesive properties can be improved by adding chlorinated alkyl carbonates. To impart tack, hydrogenated rosin resins and coumarone-indene resins can be added. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

The most common precursor to phenolic resins is phenol. More than 95% of phenol is produced via the cumene process developed by Hock and Lang (Fig. 7.1). Cumene is obtained from the reaction of propylene and benzene through acid-catalyzed alkylation. Oxidation of cumene in air gives rise to cumene hydroperoxide, which decomposes rapidly at elevated temperatures under acidic conditions to form phenol and acetone. A small amount of phenol is also derived from coal. 

Sulfur cross-links have limited stability at elevated temperatures and can rearrange to form new cross-links. These results in poor permanent set and creep for vulcanizates when exposed for long periods of time at high temperatures. Resin cure systems provide C-C cross-links and heat stability. Alkyl phenol-formaldehyde derivatives are usually employed for tire bladder application. Typical vulcanization system is shown in Table 14.24. The properties are summarized in Tables 14.25 and 14.26. 

Vulcanisation of elastomers effected by the incorporation in the compound of certain polymeric resins derived from the condensation of formaldehyde with 4-alkyl phenols. Most frequently used with butyl and EPDM compounds for enhanced heat resistance. 

Uses. In the manufacture of phenolic resins, bisphenol A and alkyl phenols, and caprolactam also used in disinfectants and antiseptics... 

Benzene is alkylated with propylene to yield cumene (qv). Cumene is catalytically oxidized in the presence of air to cumene hydroperoxide, which is decomposed into phenol and acetone (qv). Phenol is used to manufacture caprolactam (nylon) and phenolic resins such as bisphenol A. Approximately 22% of benzene produced in 1988 was used to manufacture cumene. 

ButylatedPhenols and Cresols. Butylated phenols and cresols, used primarily as oxidation inhibitors and chain terminators, are manufactured by direct alkylation of the phenol using a wide variety of conditions and acid catalysts, including sulfuric acid, -toluenesulfonic acid, and sulfonic acid ion-exchange resins (110,111). By use of a small amount of catalyst and short residence times, the first-formed, ortho-alkylated products can be made to predominate. For the preparation of the 2,6-substituted products, aluminum phenoxides generated in situ from the phenol being alkylated are used as catalyst. Reaction conditions are controlled to minimize formation of the thermodynamically favored 4-substituted products (see Alkylphenols). The most commonly used is -/ -butylphenol [98-54-4] for manufacture of phenolic resins. The tert- butyl group leaves only two rather than three active sites for condensation with formaldehyde and thus modifies the characteristics of the resin. 

Heat-setting resins cannot be plasticized by low molecular weight plasticizers. Polyvinyl acetals have been claimed for these products. American Cyanamid Co. has suggested polyvinyl acetals or butyrals in an amount of 10 to 25% of the resin for urea and melamine resins. For varnishes and adhesives, combinations of phenolic resins and polyvinyl formal are recommended. Polyvinyl acetals with higher alkyl radicals are suitable for cellulose esters and improve elasticity as well as resistance against water. 

High-boiling phenols are mixtures containing predominantly meta substituted alkyl phenols. Their boiling point ranges from 238-288°C they set to a glass below —30°C. They are used in phenolic resins, as fuel-oil sludge inhibitors, as solvents and as rubber chemicals. 

The methods used to increase the water resistance of a glass microsphere foam are basically those applied to glass-reinforced plastics, filled thermoplasts, and elastomers, viz. hydrophobic adhesion compounds are added to binder and microsphere dressing 147). The compounds added are alkyl alkoxysilane derivatives, amino or epoxy alkoxysilanes for epoxy and phenolic resins, vinyl or methacryloxy alkoxysilanes for polyester resins. The dressing agents used are aminoethoxysilanes (y-aminopropyl-... 

Oil-containing adhesives might emit fatty acid oxidation products like saturated and unsaturated aldehydes which can contribute to odor (Wilke, Jann and Brodner, 2004). Adhesives on a phenol resin base have been found responsible for odor annoyance in several office buildings in former East Berlin. Alkyl-substituted phenols, methyl, dimethyl and ethyl phenols, some of which have very low odor thresholds, have been detected in indoor air as well as in different floor samples and were most likely responsible for the off-odor (Kirchner and Pernak, 2004). 

Figure 3.5 IR spectra of (a) polyamide 6,66,610 (LPA), (b) alkyl phenol formaldehyde resin (PR), (c) reaction product PR/LPA, (d) HR, (e) IIR-PR-LPA copolymer...

---