general methods described in u s pat nos 3 447 939 4 145 532 4 426 288 4 142 913 4 144 080 and 4 145 532 the cellulose is first premixed with the desired additive before the addition of the nmmo and the subsequent removal of excess water to form the cellulose solution in a typical run 10 parts of cellulose is added to 80 parts of water containing 2 parts of dissolved sodium carboxymethyl cellulose cmc a water soluble polymer of 50 000 molecular weight since the coagulating water must be concentrated and recycled to save the nmmo one of the reasons for using water soluble polymers having a molecular weight of more than 10 000 is to be sure that none of the relatively water soluble polymer will dissolve out of the film and contaminate the coagulating water the system is mixed thoroughly to allow good intermixing of cellulose and cmc to this mixture is then added 76 parts of nmmo and the mixture is placed in a sigma blade high torque mixer under vacuum the mixing system is heated up to no more than 120 u00b0 c while vacuum is continued and excess water is removed safety note 120 u00b0 c is chosen since nmmo is known to explode violently at or above 140 u00b0 c when the active water level in the mixture reaches less than about 27 of the weight of the nmmo preferably from 8 15 the weight of the nmmo both the cellulose and cmc are in solution at the 15 weight of nmmo water level this gives a solution containing essentially 10 by weight of cellulose 2 by weight of cmc dissolved in 76 4 of nmmo containing 11 5 of water this solution containing about.