Recycling waste vegetable material, esp. rice hulls etc. - by heating under pressure with sodium sulphite, hydrolysing with sulphuric acid and converting the slurry obtd. into expanded foam prods.

摘要

Prepn. of a slurry (I) contg. a relatively high concn. of polysaccharides and glucose in the form of cellulose comprises (a) heating silica-ruch vegetable material (II) under pressure in the presence of Na2SO3 to give a slurry with pH 6-8, (b) removing the liq. from the pulp and (c) heating the pulp under pressure in the presence of Na2SO3 and H2SO4. Also claimed are the prod. (I) obtd. by the above process, and a compsn. contg. an aq. soln. of a silicate-crosslinked cellulose polymer of formula C7H12O7(OCH3.2NaHSiO3) (III); a process for solubilising (II) in order to produce slurry (I), comprising stages (a) and (c) above; and a process for the prodn. of an expanded, porous, low-wt. prod. (IV), by producing slurry (I) contg. crosslinked polymer (III) as above, blowing gas through the slurry to give an expanded foam and then drying the foam to give a rigid, self-supporting prod. (V). USE/ADVANTAGE - The process enables waste vegetable material to be converted into light-wt., expanded, cellulose-based prods. which are useful as packaging, insulation or filtration materials and for the prodn. of coating films, non-woven fabric etc. Rice hulls are esp. suitable for recycling by this process since they have a low ligning content which does not require pretreatment to remove lignin. The claims include a process for converting (II) into useful prods., by decompsn. into its basic cellular components (stage a) and hydrolysing the slurry obtd. (stage c) to give thermomechanically modified cellulose which forms a silicate-crosslinked polymer (III). Also claimed is the prod. obtd. by this process.