Hemi-acetals, their preparation and use

摘要

Hemi-acetals of general formula in which R is an alkylene radical, preferably containing 1-3 carbon atoms, x and y are integers of 1-5, n is an integer of at least 2 and R1 is a hydrogen or an alkyl group, at least one of the R1 groups being hydrogen, or alternatively two of the -OR1 groups may be removed and the remaining radicals joined together through an oxygen atom to form a cyclic structure or a carbonyl group, may be used to produce resinous materials. They may be reacted with polyhydric alcohols such as pentaerythritol, diand polypentaerythritols and the resulting product reacted with a polyisocyanate such as an arylene diisocyanate. Alternatively the hemiacetals may be reacted with phenols and the products subsequently reacted with epichlorohydrin in the presence of an alkali to form new epoxy resins.ALSO:Hydroxy-containing hemi-acetals are prepared by reacting under acidic conditions: (1) an aldehyde in which there is attached to the a - or b -carbon atom relative to the aldehyde group a hydroxyl, alkyl-sec.-amino-, primary amino or mercapto group, or an aliphatic carbon-carbon unsaturated linkage; and (2) a dissimilar aldehyde containing no reactive group other than the aldehyde group. Suitable aldehydes of type (1) are, for example, hydroxy adipaldehyde, hydroxy succinaldehyde, 2-hydroxy propionaldehyde, 3-hydroxy propionaldehyde, 3-aminopropionaldehyde, 2-hydroxy-butyraldehyde, 3-hydroxybutyraldehyde, 3-mercaptopropionaldehyde, 3-mercaptobutyraldehyde, 3 - aminopentanal, 3 - mercaptopentanal, 2-mercaptohexanal, 3-aminodecanal, 3-hydroxycyclohexanal, acrolein, methacrolein, crotonaldehyde, a -phenylacrolein, a -cyclohexyl-acrolein, 2-pentenal, 3-hexenal, 2-decenal, 2-cyclohexenal and 2-hydroxy-3-mercapto-tetradecanal. The preferred aldehyde of type (2) is formaldehyde and formaldehyde precursors such as formalin, paraformaldehyde, trioxane and methalal but other suitable aldehydes are acetaldehyde, butyraldehyde, pentanal, hexanal, octanal, dodecanal, cyclohexanal, 2,4-dimethyl-cyclohexanal, glyoxal, succinaldehyde, 1,8-octanedial, benzaldehyde, adipaldehyde and 3,5-diethylhexanal. The reaction is preferably carried out in the presence of water and/or one or more alcohols. The products of the process are hydroxy-containing hemi-acetals having the general formula in which R is an alkylene radical, preferably containing 1-3 carbon atoms, x and y are integers of from 1 to 5, n is an integer of at least 2 and R1 is hydrogen or an alkyl group, at least one of the R1 groups being hydrogen; alternatively two of the -OR1 groups may be removed and the remaining radicals joined through an oxygen atom to form a cyclic structure or a carbonyl group. In addition there may be obtained small amounts of the following compounds:- in which R is an alkylene radical, x is 1-5, and n is at least 2.