Patent GB-807636-A (GB)
Title: 3:6-di-ú¯-propylcatechol and its use in preventing premature gelation in polymerizable materials
IPC: C08K5/13
Filed: 1957-02-06
Abstract: 3 : 6 - Di - n - propyl catechol may be added as an anti-skinning agent to paints and varnishes which are subject to skin formation in closed containers during storage.  0.001 to 1 lb. of 3 : 6-di-n-propyl catechol may be added to 100 gallons of a paint or varnish containing tung oil and siccatives or driers to obtain the desired effect.ALSO:The premature gelation of an interpolymerizable mixture of monomers containing a >C=CH2 group and unsaturated polyesters is inhibited by incorporating into the mixture 3:6-di-n-propyl catechol.  The polymerizable monomers may be styrene, a -methyl styrene, p-methyl styrene, divinyl benzene; unsaturated esters such as vinyl acetate, methyl acrylate, methyl methacrylate, allyl acetate, diallyl phthalate, diallyl succinate, diallyl adipate, diallyl sebacate, diethylene glycol bis-(allyl carbonate), triallyl phosphate; esters of mono- or poly-hydric alcohols and unsaturated polymerizable monocarboxylic acids; esters of monohydric unsaturated alcohols and mono- or poly-carboxylic acids or esters of monohydric alcohols and a ,b -unsaturated dicarboxylic acids.  The polyesters may be prepared from glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1:3-trimethylene glycol, 1:2-propylene glycol, dipropylene glycol, butylene glycol or styrene glycol or mixtures of these compounds; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, aconitic acid, mesaconic acid, citraconic acid, ethyl-maleic acid, pyrocinchoninic acid, xeronic or itaconic acid or mixtures of these compounds; and non-ethylenic or acetylenic acids such as phthalic, isophthalic, terephthalic, tetrachlorophthalic, succinic, adipic, suberic, azelaic or dimethyl succinic acid. These latter acids, if used, may be in the ratio of 0.25 to 12 mols. per mol. of a ,b -unsaturated acid.  All the above acids may be used in the form of their anhydrides, if they exist, to form the polyester.  The monomers may be mixed with the polyesters to the extent of 10-50 per cent by weight of the total mixture, and the 3 : 6-di-n-propyl catechol may be present to the extent of 0.001 to 0.1 per cent by weight of the total mixture.  The inhibiter may be added to the monomer or polyester prior to mixing or it may be incorporated into the polyester during the formation of the polyester.  The stabilized mixture may be cured using about 0.01 to 5 per cent by weight of a peroxide catalyst such as benzoyl, acetyl or lauryl peroxide or tertiary butyl or cyclohexyl hydroperoxide.  In the examples, the invention is illustrated using (1) styrene and a polyester formed from maleic acid, phthalic acid and propylene glycol, the physical properties of the mixture are compared with those of similar mixtures stabilized with hydroquinone and tert.-butyl catechol; (2) a similar mixture to that used in (1) where the mixture is coated on an absorbent paper laminate which is imprinted with stripes of a carbon black ink, the samples are cured using a benzoyl peroxide catalyst an the surfaces of the samples, which contained either 3 : 6-di-n-propyl catechol, 3-iso-propyl catechol or hydroquinone, compared.  U.S.A. Specifications 2,593,787 and 2,676,947 are referred to.ALSO:The invention comprises 3 : 6-di-n-propyl catechol.  The compound may be prepared by treating catechol with an allyl halide to form a diallyl ether, heating the ether to isomerize it to 3 : 6-diallyl catechol and reducing this to obtain the desired product.  The examples describe treating catechol with allyl chloride in the presence of potassium carbonate and dimethyl formamide and with allyl bromide in the presence of potassium carbonate and acetone to give the ether, isomerizing the ether by heating at 160-170 DEG  C. for 2 3/4 hours in an atmosphere of nitrogen or by refluxing with xylene and potassium carbonate at 174-179 DEG  C. for 2 3/4 hours and reducing the diallyl catechol with hydrogen in the presence of palladized carbon at 20-60 p.s.i. The product is a solid which may be distilled at 112-121 DEG  C. at 0.2-0.35 mm. pressure.