January, 1910.] 



11 



c 



FIBRES. 



BAGASSE FOR PAPER. 



BV WlLIIAM RAITT, 



Chemical Engineer and Fibre Expert, 

 Bangalore. 



Bagasse or mecass, the refuse crushed 

 sugar canes or chips from the diffusion 

 batteries, has come into some degree 

 of prominence of late as a possible raw 

 material for paper. It may therefore 

 be useful to consider, from the collective 

 experience available, modified or con- 

 firmed by our own, how far the hopes 

 held out regarding it in some quarters 

 are likely to be justified. The growing 

 scarcity of wood-pulp in Europe and 

 America is giving occasion for a great 

 amount of research and experiment 

 with the object of finding a suitable 

 substitute, and while several have been 

 suggested which combine all the advant- 

 ages necessary to a commercial as well 

 as a technical success, it is to be feared 

 that an insufficient acquaintance with 

 the scientific and economic problems 

 evolved, has resulted in others being 

 brought forward which hold out very 

 little prospect of practical usefulness. 



It may be as well, first, to enquire 

 as to what grade or class of raw material 

 is wanted in supplement of, or in sub- 

 stitution for wood-pulp. For this pur- 

 pose, paper may be broadly divided 

 into three main grades, corresponding 

 fairly accurately with the principal 

 divisions of the raw material market : — 



(1.) The best qualities of writing paper, 

 — manufactured almost wholly from 

 linen and cotton rag. 



(2.) Inferior writing paper, book print- 

 ing and news paper, — manufactured 

 mainly from wood-pulp. 



(3.) Coarse unbleached paper, wrap- 

 ping and packing paper,— manufactured 

 from textile wastes, old sacking and 

 such like materials. 



Now, the growing demand for a new 

 material arises solely from No. 2, since 

 rag is now reserved almost exclusively 

 for No. 1, the supply is quite adequate 

 to the demand, and, apart from this, 

 no other material is likely to be found 

 which, at the same cost, combines the 

 necessary requirements of strength and 

 colour. For No. 3 where strength only 

 is r< quired, the market is also fully 

 supplied, and the steady development 

 of textile industries, with the resultant 

 continual increase in the output of 

 wastes, seems likely to keep it so. 

 But although the new demand is con- 

 2 



fined to No. 2, it represents about 75 % 

 of the whole, and at present uses up 

 about six million tons per annum, so 

 that there is plenty of scope for a 

 material suitable for it. In this case, 

 suitability means that it be bleachable 

 at a low cost. 



Bagasse contains about 50 % of avail- 

 able cellulose. Our own investigations 

 of it have yielded from 46 to 50 %, and 

 with a comparatively mild soda treat- 

 ment it could be depended on to give, 

 in mill practice, an average yield of 

 45 % of air dry unbleached cellulose or 

 pulp. So far, it appears to fill the bill, 

 but there is more than that which goes 

 to the making of a good pulp for No. 2 

 class. 



With all fibre-yielding plants, there 

 is a point or period ot growth at which 

 the fibre is at its best, not only in 

 quantity and quality, but (what is of 

 serious importance to the paper-maker) 

 in uniformity of its qualities throughout 

 the whole plant. The pulp to be pro- 

 duced must be of uniform quality, and 

 this cannot be got if there are serious 

 differences in the nature of the raw 

 material as between one part and 

 another of the plant- With plants 

 grown primarily for fibre, a period can 

 generally be fixed on for cutting at 

 which the fibre is at its best, not only 

 in strength and colour, but also in uni- 

 formity throughout the whole plant. 

 But with cultivation primarily for other 

 uses, the case is very different. Gener- 

 ally, when fibre only is wanted, the 

 plant is at its best when fully mature 

 but not ripe. Where fruit or seed is 

 the chief object the mature stage of 

 the fibre is passsd ; where juice is 

 wanted, it has not been reached. 



The stage at which sugarcane holds 

 its maximum saccharine contents ap- 

 pears to coincide with a state of partial 

 and irregular maturity of the fibre. 

 While the fibres on the outside, or just 

 under the skin of the cane are firm, long 

 and good, of strength though somewhat 

 harsh, those from the interior are short 

 and weak. It therefore presents the 

 most difficult of problems to the paper- 

 maker. Since the chemical treatment 

 must be uniform, it follows that it 

 must be severe enough to reduce the 

 outer fibres completely, thereby largely 

 destroying the inner ones, or it must 

 be mild enough to conserve the latter 

 and leave the former only partially 

 resolved into pulp. In the first case the 

 yield is largely reduced, and what re- 

 mains is expensive to bleach because 



