MANUFACTURE OF PULP AND PAPER.

Hokitika Guardian, 2 August 1928, Page 4

MANUFACTURE OF PULP AND PAPER.

FROM NEtV ZEALAND WOODS. The pulp and paper tests upon New Zealand woods, recently supervised in North America by Mr A. R. Ehtriean, engineer of the New Zealand State Forest Service, consisted of two separate studies, one a laboratory study and the other a commercial pulp and paper mill trial. The Government received a report upon the laboratory study some months ago, but withheld it from publication, since some of the conclusions were likely to be considerably modified by the results of the com, therein! mil! trials. With the receipt this week of a report upon the pulp and paper mill trials, the Government finds its action in this regard justified, and Air Entrican is now engaged in modifying and combining the results of the two studies, so that the complete report upon the work should be ready in about three weeks’ time. In terms, however, of the agreement entered into with the Government of the United States, which undertook the work, it will he necessary to submit to their Forest Products Laboratory at Madison, the re-written report for approval. This is expected to delay the actual publication of the report until the end of September. In the meantime, the following statement summarising the results and outstanding features of the work, is issued for public information. SUMMARISED RESULTS.

The reports show that commercial grades of newsprint may he produced from insignis pine and tawa, and oi

kraft papers (i.e., wrappings, etc.) from rimu, insignis pine, and a number

of other woods. Other classes of paper, such as book, fine printings, etc., may also be manufactured from some of these woods, but since they aie consumed in comparatively small quantities, they do not command the same attention as do newsprints and wrappings, which lead all papers in quantities used. PURPOSE OF TESTS. It is not enough to know how to grow trees: it is just as necessary to know how to use them. Thiftv veais ago the Government initiated a treeplanting programme which has gained momentum steadily, until to-day the Forest Service has planted some 136,000 acres, and expects to establish this 1028 planting season, a further 03,000 acres. The Forest Service is administering, too, a forest domain of over 7 million acres. All these plantations and forests are yielding large volumes of Wood, for Which it is necessary to develop profitable markets. Some of the forest crop goes into building and constructional timber, some into poles and fencing posts, and some into fuel wood. Yet there still remains material in the shape either of woods and mill waste, or of unused species, or of thinnings and improvement cuttings for which no outlet has appeared available, largely because we did not know bow or for what purpose to use them.

An intensive study of the situation indicated that the most promising avcniie for the utilisation of much of the material, lay in the pulp and papei industry, and the Government decided accordingly that it should first ascertain if the principal woods were suitable for this purpose. flow to carry out the work was the first problem. Two alternatives presented themselves! that of building a laboratory In New Zealand, or, alternatively, of arranging for a recognised and established laboratory abroad to undertake the work. Eventually, the second alternative was adopted. Not only did it promise to be several times more economical, this because the capital cost, of a lbed! establishment would he high, and the development of a good operational technique very costly, hut the resvilts from a recognised laboratory would be more readily acceptable by cotnriiereial pulp and paper financiers who might be interested iii the development of the industry in New Zealand. Most, unexpectedly. the Government of the United States of America was found to be interested in some of the problems involved in the work, aiicl the Forest Service entered into an agreement whereby the Forest Products Laboratory at .\iadisc4. Wisconsin, tljo foremost pulp and paper research institution of its kind, in the world, undertook to study the pulping and papermaking properties of a niiliiber of our woodsT Mr Alex. K. Entrican Was de-

puted to assist with the work, and to make all industrial survey of the pulp and paper business in North America. LABORTOEy AND M.11.L TESTS. The laboratory tests initiated at

Madison eventually proved so suceesslul that the Government decided to carry the study to a logical conclusion by exteHdiii<i; its scope to include a mill scale test under commercial operating conditions. Thi.scatter study included a pulping and paper-making trial at the Ladysmith (Wisconsin) plant of the Great Western Paper Cohijidny. ihe results of the luhbrhtory mill linn trials are discussed concurrently. WOODS TESTED. Of the woods studied, two species are indigenous to New Zealand : riniu (daervdium cupressinum), a soituood, and tawa (Beilschmiedia tawa), a hardwood; and four introduced softwoods: insignis pine (pinus rndiata), Austriali pine (pinus austriaca), Corsican pine (pine laricio) and European larch (Larix europea). The two natives species limit and tawa—and the introduced softwood —insignis pine—were studied more intensively than the others, the riniu because it is tbe most widely distributed and commonly used softwood in New Zealand, and the insignis pine since it is-the most widely propitgated species in tbe extensive man-made foiests established by Government add I private interests. The tawa was studied ' not only as the principal hardwood of the North Island forests, i>ut iis being typical of a group of hardwoods—they all have the saiiie type of Abie—such J as blue gum (eucalyptus glomus) and ! Tasmanian stringybary (E.obliqua). From a pulping point of view a softwood differs from a liardwood primarily in the shape of its fibre, that of tbe softwood being :dniparatively long and slendek, with a Uniform cross-section throitgholit its length, while that of the hardwood is very much shorter, thick at the centre of its length, and tapering away to fine ends. The three remaining woods—Austrian and Corsican pine and European larch—are some of the minor species included in the Forest Service plantations. Other species included in the Government and private forestatioii efforts fire Douglas

fir (Pseudotsuga Douglasii), and western yellow pine (Pinus ponderosa), but in view of the previous studies on these woods made by the Madison Forest Products Laboratory, further work was considered necessary. HOW WOOD IS PULPED. In general there are two principal methods of pulp manufacture—mechanical and chemical. The mechanical is accomplished bv pressing short logs of wood from which the bark has been removed against a rapidly revolving grindstone. The axis of the log is placed parallel to the axis of the stone, which is kept cooled and the pulp removed by a si lower of water sprayed continuously on tbe stone face. The product is variously termed “wood pulp,” “ ground wood,” and mechanical pulp,” and finds intensive use in newsprint paper, cheap catalogue and hook papers and hoards. Ordinary newsprint “ furnishesfcdritain _ from 60 to 85 per cent of it, the amount being limited only by the .strength requirements of the sheet, which are met

by certain admixtures of chemical pulp. The principal items of cost are the power used in grinding, and the wood. The product, however, is of a somewhat evanescent character. Containing, as it does, all the wood substance, it is subject to deterioration, and particularly to discolouration. It is thus limited to papers designed for temporary use, or for filling in with more durable fibres. Ground-wood fibres, however, possess certain qualities of opacity and stiffness which are often .valuable.

Chemical pulp is produced by removing all bark, decayed Wood and dirt, etc., from logs, chipping the cleaned wood, and cooking the chips with various liquors at high temperature and under pressure. For a light coloured fibre suitable for- newsprint, etc., a sulphite liquor is employed; for dark, tough fibres used in wrappings, etc., a sulphate liquor; and for light coloured hardwood fibres suitable for book and other bulky papers, a soda liquor. The chemicals dissolve away from the fibres the encrusting material which holds them together, so that in general, fibres produced chemically are much longer afid stronger than those produced mechanically, where one fibre is torn from another by the grindstone, and so considerably damaged in the process. l>D LPING TESTS—GENERAL. In planning the pulping tests, throe major objectives were set up, their importance being considered in the order named: 1. To produce a pulp or pulps suitable for newsprint. 2. To produce a satisfactory kraft pulp for wrappings, etc. 3. To produce bleached chemical pulps for fine papers. In pursuance of the first objective, pulping tests were made by means of the mechanical, sulphite and combined mechanical-chemical processes, the greater part of the work being devoted to insignis pine and tawa ns the most suitable species available. Iliimi, larch and all of tho pines, were pulped by the sulphate process in order to evaluate their possible utility for kraft papers. Pulping tests by the soda process were limited to tawa. Bleached chemical pulps were produced from insignis pine sulphite and sulphate pulps, and from tawa sulphite and soda pulps.

GROUND-WOOD PULPING TRIALS

In general, ground-wood pulps from insignis pine were found equal to spruce in yield and strength, but inferior from tho standpoint of colour and dirt. The colour, of course, is an inherent property of the wood, but the dirt is due to the prevalence of knots nnd core or pith rot, so that it should he controllable within certain limits. In the logs Used for tho original laboratory test, the core rot was a serious factor, whereas in the second shipment used for tho mill tests, it was almost negligible; Clearly the problem is one for tho silviculturist to solve.

Being a hardwood and very short fibred, the tawa yielded a pulp much inferior in strength to both insignis pine and spruce. At the same time; the pulp was of good colour, and in the case of immature trees, comparatively free from dirt, so that for a filler it is fairly satisfactory. Even from the second shipment of jnilpwood, comprising a fairly large proportion of rimture logs in which a black discolouration was quite common, .a fairly clean light coloured pulp was obtained at the pulp mill, since the black dye proved to he highly water soluble. The tawa yield per cord was about 10 per cent higher than In tho case of spruce. Neither in the ease of insignis pine nor of tawa was the power consumption for grinding excessive. Tho rimu was found too dark, and the larch and other pines .tod patchy to yield a satisfactory grndo (if groundwood. SULPHITE PM PING TRIADS.

Unbleached sulphite ediistitutes from 20 to 30 per cent ot tlie average newsprint paper, and in lljib with the major objective of the study, tlie principal effort in the sulphite pulping experiments was directed towards the production of a grade of pulp statable for newsprint. Incidentally; Some attention was given to the biotic-lung of the pulps produced, in nocoi-daiiee with the minor objective of jn-dducitig a bleached sulphite stock.

Only three woods—iiiiiii, tiitvii and insignis j>inc—were successfully reduced by this process. Tlie expbriuicuits with rimu iiuliehted that this species can he readily reduced to pulp by the sulphite method, liiit the product is too dark tor use iii hefrSpriiit unbleached. It could, howevel-, lie Used foi- sulphite wrappings, etc.

Insignis pine was reduced to a suitable quality of pulp for use in newsprint paper without bleaching, the yields and strength quality being comparable with those of sulphite pulp from white spruce. Although the pulp produced at the laboratory was inferior in colour to spruce pulp, that manufactured at the Lhdysihith pulp mill aliiiost equ ailed tlie coHiihercial grades of spruce sulphite in colour. The yields per cord, based on both the laboratory and mill tests, are fully as good as those obtained from the spruce. Immature tawa was readily pulped under laboratory conditions, the nature of the product being determined by the cooking methods used. By employing an li-iiour cooking schedule, a satisfactory pulp for hook paper, blenching easily, was produced. Reduction of the total time to about 9 hours gave a pulp suitable for newsprint purposes, and obtainable in high yield. In the mill tests tlie large proportion of mature wood used yielded a somewhat differeht class of pulp, still of good colour, hut rather “ sliivey ” in character. It was, however, actually refined without difficulty, find in all probability altered cooking conditions will reduce or even eliminate this small difficulty. The yields per cord in both series of tests were from 10 to 20 per cent higher than for spruce. SULPHATE PULPING TRIALS. All five softwoods—liiiui, Cdislcnn pine, Austrian pine; iiisignis pine, and European larch—were reduced without difficulty hy tlie sulphate llietliod, and a pulp produced comparing favourably with the So-called “ Niimber One” kraft pulp on the North American market.

Itimu produced the best pulp, with the woods following in the order given above. Riniu slabwood yielded a. slightly inferior pulp to that secured irom round wood.

The semi-kraft process differs from the regular sulphate process in that the cooking liquor is impregnated iiito the chips under pressure prior to the steaming or" cooking action, and all unabsorbed chemical is removed before actual pulping begins. The chips are not completely pulped, but merely softened, the final pulping being effected hy disintegration in a grinding device, such as a rod mill. Riniu, insigiiis pine and larch, were pulped by this method, arid the savings in chemicals and increases in pulp yield are remarkable, in view of the quality of the pulp produced, which, although darker and somewhat inferior to the straight sulphate pulps, is most promising for lower grades of kraft papers and boards. SODA PULPING TESTS.

Pulping experiments by this process were limited to tawa. Not unexpectedly, the tawa soda pulps were weak, but they possessed excellent bulk and opacity, and will serve for book and similar grades .of paper. SEMI-GHFAiICAL DULPING TESTS.

Tawa was also pulped by the semibtieiilletii process; 4hicli is quite similar to the semi-kraft process already de-

scribed; except that a iieiitral ihstchd of an alkaline liquor id used; Llib objective was a light colOlired pulp suitable as a substitute for the tawa sulphite pulp, but tlie stock produced was unsatisfactory for this purpose, both on account of colour atid cleanliness, although liavihg excellent possibilities in the field of fibte hoard, cSiitainer and building boards, etc. PAPER-MAKING TESTS.

Practically all tile paper-making work, botli iii the laborntoi-y and at the mills, was c-dticeht fated Up'dfi the production of newsprint from various pulps and furbishes. lit the case of both wrappings and papers using sulphite or soda bleached stocks, the pulps were so similar to the standard North American and Europehii pulps that extensive paper-making experiments were unnecessary, aiicl only .si few laboratory trials were made as demonstrations. All wei'e quite successful. INSIGNIS PINE NEWSPRINT.

Tho first laboratory efforts to produce a newsprint, followed staiidai-d North American and European pi-notice and combined varying proportions of groundwood and sulphite pulps, papers of corresponding “furnishes” being produced from both spruce and insignis pine. The insignis pine newsprint exceeded in strength the spriiee newsprint, hut was of somewhat poorer colour, and when made from pul])wood containing core rot, knots and blue stain, was dirtier. Cleaner papers resulted from pulpivood from which these defects were eliminated, and, wlien i-iin over the printing presses of the Wisconsin State Journal, lielulved exceedingly well, and wet-C*declared by the publishers to he equal to the average commercial newsprint in regard to colour, bursting strength and printing qualities. Certainly, had the pulpwood used for the laboratory tests been an free from core or pitli rot as that iisccl by the mill trials, the complaints as to dirt would have been much less serious, and perhaps even negligible. Summarised, it would appear that a good commercial grade of newsprint, consisting of 25 per cent sulphite and 75 percent ground-wood, may be produced from insignis pine. INSIGNIS I’INE-TAWA NEWSPRINT In their initial stages the efforts to produce a satisfactory insignis pine news-sheet, were discouraging, and attention was directed to the production of a new type of newsprint, based on a study of the theory of paper formation, and on experiments by Miller in America, and Benjamin in Australia, on the use of hardwoods for newsprint. From this work a theory was evolved and experiments instituted to tost its soundness. In ordinary newsprint practically the whole of the tearing strength and a great part of the tensile strength is given by the long sulphite fibres of the softwood.

Ground-wood, on the other hand, contributes opacity to the paper, and gives it a good bursting strength. How to obtain the same results, using a mixture of softwood and hardwood pulps, was the problem to he solved. The experiments confirmed the theory that a small amount of long fibred insignis pine sulphite’pulp (about In per cent) should still ho used to give tearing .strength to the sheet, that hardwood sulphite from tawa (about 50 per cent) should ho substituted for a largo part of the soft-wood ground-wood to give bursting and tensile .strength, and that a fair proportion ol hardwood ground-wood from tawa (about 35 per cent) should provide tho necessary opacity. So successful wore the initial experiments along these lines that attention was concentrated upon tho problem of producing a combined soft-wood-hardwood newsprint, and eventually some very fine sheets equal to an i hotter than the commercial softwood newsprint, were produced and run over tho presses of tho Wisconsin Journal. Tlie laboratory test, however, lacked one very important essential. All the papers were produced on a slow running machine, and considering tho faci that this furnish of combined softwood and hardwood sulphites and hardwood groundwood was an altogether new one it was thought advisable to extend thu portion of the study to a commercial scale, and to have the paper produced on full-sized fast-running machines. The Government duly made arrangements to this efleet through Air Eutrioan and the Aladisou forest Products Laboratory, a shipment of insignis pine and tawa being pulped by the Great Western Paper Company at their Ladysmith plant, and made into paper at the Wisconsin Rapids plant ol the Consolidated Water Power and Paper Company. The commercial trial lully justified itself, liot only in producing a newsprint whose colour, strength, cleanliness and finish was equivalent to that of standard news, but in solving many practical pulping and paper-mak-ing problems which had not been apparent in the laboratory tests, and which will be reflected in tlie design aikl operation of any pulp and paper mill which may be found feasible in this country .One remarkable feature about the combined insignis-tawa pulps is the high finish which they may he given, suffieieiit indeed to make the paper useable for machine finish book or rotogravure paper. Some of this M.F. book and some dry finish wrapping paper was indeed actually produced at the conclusion of the newsprint runs. FUTURE DEVELOPAI ENT.

Originally the study was made as one df the management problems in connection with the State forests and plantations. With its successful conclusion, the logical step is to initiate a further stiuly which will cover the actual comlriercial possibilities of establishing a pulp ft lid paper industry in New Zealand. in tidditibh to making a study of the technique of pulping and papermaking processes; 3lr Eritrican has been engaged upon ail investigation of the economical and financial aspects of thb industry both in North America arid Eiiiopc, and the Government will how carry this work to a logical corieirision by initiating a new study whereby lie will lie seconded from his usual duties to make a detailed field examination of the commercial possibilities in promising localities. The study will cover wood supplies, transportation, chemical supplies, water, power and fuel, manufacturing and other- facilities, labour conditions, etc., and will probably lake soiiie six months to complete. A word of caution regarding tlie tendency to over-enthuse oii the cdiniiiCrciai possibilities of the industry, is very necessary at tiiis juncture. Tile industry is such a highly technical brie, and involves such a large capital investment. that the utmost care must be exercised in its establishment in New Zealand, otherwise ft precipitate failure will unduly prejudice the later development and expansion of the iridustry. To achieve economical results, mills should be of considerable size. For instance, the minimum size for a complete newsprint mill (i.e. both pulp and paper) is probably 100 short tons (2,000 lbs) per day, if not more, and this would involve a capital investment of about £1,000,000. New Zealand's consumption of paper, however, is small, and further than that, tlie world market for both pulp and paper, is in a parlous condition, and unlikely to recover for at least five years. Glearly we must proceed cautiously, and lay a sure foundation for the permanent wellbeing of the industry, relying in the early stages on our domestic and nearby markets, and leaving the development of world markets to a more favourable opportunity. , ~ appreciation.

Botli tlie laboratory and pulp and paper mill trials have been beset with

difficulties throughout, and an expression of ithprfecititibii Is due to the staff of Madison Forest Products Laboratory for their tenacity of purpose in bringing to a successful conclusion a problem of no small niagnitude. The members of the staff—all of them’ arc prominent in different lines of pulp and paper research—engaged upon the work were: C. E. Curran, Chemist in Forest Products; E. R. Schafer, Associate Engineer in Forest Products; AY. H. Monsson, Associate Chemist in Forest Products; Cl, H. Chidester, Assistant Engineer in Forest Products, and P. l£. Baird, Associate Chemist in 'Forest Products. The work was supervised by Mr Clark C. Heritage, in charge of the Section of Pulp and Paper, in co-operation with Mr A. R. JCntrican, Engineer of the New Zealand State Forest Service.