Carboxymethylcellulose and its salts

39.12 - Cellulose and its primary forms. chemical derivatives, not elsewhere specified or included, in - Cellulose acetates : 39 12.11 - - Non-plasticised - - Plasticised 3912.20 - Cellulose nitrates (including collodions) - Cellulose ethers : 39 12.31 - - Carboxymethylcellulose and its salts 3912.39 - - Other 3912.90 - Other 3912.12 (A) CELLULOSE Cellulose is a carbohydrate of high molecular weight, forming the solid structure of ve etable matter. It is contained in cotton m almost a pure state. Cellulose not elsewhere speci ed or included, in primary forms, falls in this heading. I Regenerated cellulose is a glossy, trans arent material usually obtained by precipitation and coagulation when an alkaline solution o cellulose xanthate is extruded into an a c ~ dbath. It is usually in the form of thin, transparent sheets which are classified in heading 39.20 or 39.21, or of textile filaments of Chapter 54 or 55. ! Vulcanised fibre, which is produced by treating paper or sheets of cellulose pulp with zinc chIoride, is generalIy in the fonn of rods, tubes, sheets, plates or strip and is therefore also excIuded (generally heading 39.16,39.17,39.20 or 39.21). (B) CHEMICAL DERIVATIVES OF CELLULOSE This group includes chemical derivatives of cellulose which serve as a basis in the manufacture of plastics as well as for other purposes. The principal chemical derivatives of cellulose, whether or not plasticised, are : (1) Cellulose acetates. These are prepared by treating cellulose usually cotton linters or dissolving ades of chemical wood pul ) with acetic anhydri e and acetic acid in the presence o a catalyst (e.g., sulphuric aci$. With the addition of plasticisers they can form plastics which are non-inflammable and suitable for injection rnouldin . They are commonly presented in the form of owders, granules or solutions. Cellu ose acetates resented in the form of sheets, rods, tubes, etc., are excluded (generally ieading 39.16,39.17,39.20 or 39.21). P hn, f (2) Cellulose nitrates (nitrocellulose). These products (usually cotton linters) with a mixture of nitric and inflammable and the more highly nitrated varieties ( transported darn ed wiglcohol, or plasticised wi phthalate of alcohol forms celluloid. Celluloid is other extruded forms, and is then excluded from this heading (generally heading 39.16, 39.17, 39.20 or 39.21); it is not suitable for injection moulding and is therefore not put up as a moulding powder. Cellulose nitrate mixed with other kinds of plasticisers is widely used as the basis for varnishes, and for this purpose may be presented in the form of dry or pasty extracts. Solutions consistin of nitrocellulose in a mixture of ether (diethyl ether) and alcohol (ethanol) are collo ons which are also included here. If the solution is partly evaporated celloidin is obtained in a solid form. %r (3) Cellulose acetate butyrate and cellulose pro ionate. These are cellulose esters forming plastics of the same general character as those ormed with cellulose acetate. P (4) Cellulose ethers. The most important are carbox ethylcellulose, methylcellulose, and hydroxyethylcellulose. These are water-soluble an are used as thickeners or as glues (see the General Explanatory Note to this Chapter, exclusion ), for the classification of lues). Other cellulose ethers of commercial mportance lnc ude ethyl cellulose whicf is a lightweight plastics. d" P Plastics chemically derived from cellulose generally need the addition of plasticisers. For the classification of olymers (including copolymers), chemically modified polymers and polymer blends, see the eneral Explanatory Note to this Chapter. cP