Patent GB-1282526-A (GB)
Title: Grafting vinyl compounds to cellulosic materials
Inventor: BARBEHENN HERBERT STEPHEN
IPC: C08F251/02
Filed: 1970-10-23
Abstract: 1282526 Graft polymers of cellulose EASTMAN KODAK CO 23 Oct 1970 [24 Oct 1969] 50423/70 Heading C3G A process for the production of a grafted cellulosic product comprising: (a) initiating a grafting reaction by blending together in an acidic aqueous reaction medium (i) a cellulosic material which is cellulose, a cellulose ester, a cellulose ether or a cellulose ether-ester, (ii) a vinyl compound capable of being grafted to the cellulosic material in the presence of a redox catalyst and (iii) a ceric ion-nitric acid redox catalyst, and (b) maintaining the temperature of the reaction medium sufficiently high and for a sufficient period of time for the cellulosic material and the vinyl compound to interact to thereby form the grafted cellulosic product; is characterized by initiating the grafting reaction only after the ceric ion-nitric acid redox catalyst has been aged for a sufficient time to have approached to within 5% of its maximum stable level. Instead of the reactivity of the eerie ionnitric acid redox catalyst diminishing to zero with time it has been found that its downward degradation is reversed and after a period (about 4-5 hours from the time when the catalyst system was prepared) attains a "reactivity" level which is stable for many hours thereafter and is at a maximum and it is this high, stable level of reactivity which is defined as the " maximum stable level " for the catalyst system. This maximum level is maintained for at least 1000 hours. Preferred vinyl compounds are acrylonitrile, methyl methacrylate, ethylmethaerylate, butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, divinyl benzene, vinyl acetate, acrylic acid, acrylamide, α-chloroacrylonitrile, and mixtures thereof. Preferred cellulosic materials are regenerated cellulose, cellulose acetate, cellulose butyrate, cellulose prioponate, cellulose acetate butyrate and cellulose acetate propionate. The weight ratio of vinyl compound to cellulosic material is preferably at least 0À1:5, more preferably at least 0À5:1. It is preferred that the temperature of the grafting blend be maintained at least 30 F., whilst more preferably, the temperature employed is at least 35 F. and the period of the grafting reaction is at least 5 minutes. Nitric acid as one component of the redox catalyst is used in an amount equal to at least 0À01 molar, more preferably 0À01-1À0 molar, concentration based on the aqueous portion of the grafting blend, ensuring a pH below 2À0, whilst the preferred concentration of eerie ions, on the same aqueous basis is at least 0À001 molar, more preferably 0À001-0À1 molar Specific examples refer (I) to the grafting of cellulose acetate with acrylonitrile and (II) to the grafting of cellulose pulp with methyl methacrylate in which both examples the catalyst system was prepared 6 hours previous to being added to the reaction slurry. The cellulosic material, water and eerie ion-nitric acid redox catalyst may be blended together before the vinyl compound is intermixed with cellulosic material or alternatively a mixture of the cellulosic material, water and vinyl compound is formed before the eerie ion-nitric acid catalyst is blended into the mixture.