| 摘要 |
1520134 Aqueous phenolic resole dispersions UNION CARBIDE CORP 5 Aug 1975 [6 Aug 1974] 32723/75 Heading C3R An aqueous dispersion contains dispersed particles of a substantially water-insoluble phenolic resole in water, gum ghatti, and a thickening agent other than gum ghatti, substantially all of the particles having diameters below 25 microns, wherein the gum ghatti is present in an amount sufficient to stabilize the dispersion of resole particles, and wherein the thickening agent is present in an amount such that the viscosity of the dispersion is at least 500 centipoise at 23‹ C. The dispersion may be prepared by reacting a phenol with an aldehyde in the presence of a basic catalyst for a period sufficient to produce a water-insoluble phenolic resole, and dispersing the resole, in situ, in an aqueous medium-containing gum ghatti and a thickening agent, wherein the aqueous medium contains sufficient water to enable a phase inversion to occur during the dispersing step. Preferably the resulting dispersion is heated for a period of time sufficient to increase the weight average molecular weight of the resole to 400- 3000, provided that the pH of the reaction mixture is not greater than 9 prior to the dispersion step. The amount of resole in the dispersion is preferably not greater than 50% weight, based on the resole plus water. The phenol may be monohydroxybenzene, an alkylphenol, a halophenol, p-phenylphenol, styrenated phenol or a bisphenol. The aldehyde may be formaldehyde or a formaldehyde donor, e.g. paraformaldehyde or hexamethylenetetramine, acetaldehyde, furfural or acrolein. Preferably 0À5-4 moles of aldehyde are used per mole of phenol. The basic catalyst may be an alkali metal or an alkaline earth metal hydroxide, oxide, or carbonate, an ammoniacal compound or an amine. The thickening agent may be guar gum, gum carrageenin, algin gum, locust bean gum or a water-soluble polymer, e.g. an ethylene/maleic anhydride copolymer, ionomers, polyacrylamide, or methylvinylethermaleic anhydride copolymer, and is generally used in an amount of 0À1 to 1 pbw per 100 pbw of phenol and is sufficient to increase the viscosity of the dispersion to at least 500 cp at 23‹ C. The gum ghatti is preferably used in an amount of 0À5 to 5 pbw per 100 pbw of phenol. The dispersions are infinitely dilutable with water. In the Examples aqueous dispersions are prepared by the preferred process above using as the phenolic component:- either phenol, bisphenol A, p-tert-butylphenol or a mixture of phenol and p-nonylphenol; as the aldehyde component: aqueous HCHO; as the neutralizing agent to bring the pH of the reaction mixture to below 9:- aqueous H3PO4 or H2SO4; as the thickening agent:- guar gum, locust bean gum, sodium alginate or ethylene/maleic anhydride copolymer; and gum ghatti as the interfacial agent. Uses:- Adhesives, and coating compositions, e.g. containing an acrylic latex. |
