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“ refining engine,” a machine of American origin ; the names associated with the invention of these engines are those of Kingsland, Jordan and Eustice, Gould and Marshall. The type which is used very extensively in this country is the Marshall pulp refiner of Messrs. Bentley and Jackson, Limited (Fig.
19 and 20), which consists of two cones, a | larger stationary A', and a smaller revolving
one A, both provided with beater knives. The smaller is placed inside the larger cone and thus the pulp, during its passage between the
the drumwasher, b, the channel, c, and the propeller d.
The Tower beating engine (Fig. 18), patented by Messrs. Masson, Scott and Co., Ltd., is another modern beater in which the stuff is
two, is acted upon by the knives. Before size and colouring matters. It is therefore leaving this engine, the fibres have to pass obvious that the quantity added should never between the knives fixed on a revolving disc, B, exceed the amount required for the decomposi. and the knives, B', on the inside of the chamber tion of the bleach present. Hypochlorite in in which this disc is enclosed.
the pulp may be readily detected by means of Considerable experience is required to judge potassium-iodide-starch paper, which devewhether a pulp has been sufficiently beaten. lopes a characteristic blue colouration with It is the practice to take a small quantity of free chlorine. the pulp out of the beater and to reduce it with water in a small hand bowl ; by this means
SIZING. the degree of disintegration of the fibres may The sizing of the pulp is the next of the be readily ascertained.'
operations conducted in the beater, which In the production of high-class papers and calls for consideration. Paper made from in the dyeing of delicate shades it is of the fibres in a pure state, as produced in the greatest importance to employ water of great | beating engine, will not resist water or ink; purity, especially in the beating.
the pores and the canals in the fibres on the
ANTICHLOR. Although the removal of bleach and of other impurities formed during the bleaching operation is most completely effected by subsequent washing, it is, in inany instances not found possible to carry the washing far enough. Recourse has therefore to be made to decomposition by means of the so-called “antichlors"; the chemical agents mostly in use for this purpose are sodium thiosulphate and sodium sulphite.
With calcium hypochlorite, the first of these salts forms sodium sulphate and calcium chloride, whilst the second one gives calcium sulphate, sodium sulphate, and sodium chloride. On account of the injurious action of the free hydrochloric acid which is formed by double decomposition when thiosulphate is used as antichlor, sodium sulphite has found by far the widest application. Though an excess of antichlor is frequently considered harmless, it may exert an injurious action on
one hand, and the interstices between the fibres in the sheet of paper, on the other hand, absorb liquids very rapidly by capillary attraction. The object of sizing is to fill up the pores and the interstices and thus to make the paper, to a certain extent, ink and water resisting. Wiesner has ascertained that starch was used for the sizing of papers, in very early times, whilst, at a later period glue was employed for surface sizing.
In engine sizing—so called because it is conducted in the beating engine-finely divided rosin is precipitated in the paper pulp. Illig, who invented this method of sizing at the beginning of the last century, recognised that its efficacy is due to the precipitation of free rosin in a state of very minute division ; Wurster, Conradin, and Lunge have shown that Illig's view was quite correct.
The “ rosin size,” or “rosin soap,” as it is termed, is prepared by dissolving rosin in soda in a double-jacketed pan which is heated by
Starch, especially in the manufacture of high consists of a mixture of different fibres, the class papers and of papers which have to be introduction of a suitable loading material heavily loaded. The size should be diluted may be found necessary. Loading also helps with water before being added to the beater; to 'make a paper less transparent, and the after the addition, sufficient time is allowed for smoother surface produced in finishing is it to mix completely with the pulp and the size better adapted to the requirements of printis decomposed by means of alum or aluminium ing. In choosing a loading material two sulphate. Free rosin is precipitated and basic points have to be borne in mind, namely, the aluminium sulphate remains in solution ; rosin properties of the paper for which it is to be is also precipitated if sulphuric acid is used used, and the cost of the material itself. The instead of alum, as has been done by Conradin latter point will, to a very large extent, depend and others for sizing papers.
upon how much of the material in question is The amount of alum or aluminium sulphate actually carried by the pulp. added is invariably in excess of the equivalent China clay (kaolin), which consists essenrequired for the decomposition of the quantity | tially of aluminium silicate, is the most comof rosin soap used.
monly used loading material. Various agents have been proposed as sub Pearl hardening (sulphate of lime), imparts stitutes for rọsin size. Of these “viscose” | a very superior finish to papers and is there(cellulose sulpho-carbonates) calls for special fore employed in the manufacture of highattention. The preparation of this cellulose class papers. Its use is, however, rather compound, which is soluble in water, has been costly, owing to its solubility in water. described in the first lecture. The necessary Heavy spar, blanc fix (barium sulphate), is quantity of viscose is added to the pulp and one of the most useful loading materials, giving allowed to become thoroughly mixed; the the paper very valuable properties. It may decomposing salt, either magnesium sulphate be added either in form of a paste, or better, it or zinc sulphate, is then added, and gelatinous may be precipitated in the pulp hy decomcellulose is precipitated which acts as a strong posing barium chloride with Glauber's salt. sizing agent. In most instances it is found A galite, which consists essentially of magnecessary to add a small quantity of rosin nesium silicate, possesses a fibrous structure size. Papers which have been sized with similar to that of asbestos. It imparts a viscose show a remarkable increase in tensile soapy feel to papers and gives an excellent strength, but the slight discoloration, due to finish. Owing to its fibrous structure nearly decomposition products of viscose, has up to the whole amount of this material added is the present time prevented its being used for carried by the pulp. the sizing of white papers.
Starch. — As already mentioned under Casein, prepared from milk, is another sizing sizing, starch is frequently used together with agent which may be added in solution to the the rosin soap; it is, however, quite safe to pulp, and which is readily precipitated by alum. count it among the loading materials. A Casein, although excellently suited for paper large portion of the starch added to the pulp sizing, is but little used on account of its cost. is lost; but, although expensive, its use for Other sizing agents, such as silicate of soda, high-class papers cannot be dispensed with. aluminate of soda, ammonium albumen, wax, The feel of papers loaded with starch is not paraffin, &c., are very rarely used.
unlike that of tub-sized papers ; they do, not,
however, possess the characteristic waterLOADING.
resisting properties of the latter. Mineral substances are often added to the paper pulp whilst in the beating engine ; this operation is known as “loading” or “filling."
COLOURING. One of the objects of the addition of loading The last process which is conducted in the materials is the cheapening of production beater consists in dyeing the paper in the by the substitution of fibres by a cheaper pulp. The paper fibres, being nearly exclumineral substance; in many instances, how- sively of vegetable origin, show much less ever, the addition of loading materials is, for affinity towards colouring matters than do the other reasons indispensable. Certain mineral animal fibres, wool and silk. On account of colours used in paper dyeing act at the same the minute state of division of the fibres in time' also as loading materials; to produce the pulp, colours are, however, generally uniformity of shade in the dyeing of pulp which speaking, much more readily taken up than is the case in the dyeing of the same fibres | The artificial mineral colours may either be in the form of yarn or cloth.
| prepared outside the beater and then added to The affinity of the various fibres towards the pulp, or the precipitation of some of these colouring matters differs considerably, a colours may be actually effected in the beater. factor to be taken into consideration in the Wherever convenient preference should be manufacture of coloured paper which consist given to the latter method, the precipitation of a mixture of various kinds of fibres. To l of the colour as well as the fixing being partly secure a level appearance of the surface of accomplished in the fibres. papers of this description, mineral loading Some of the most important paper colours materials or mechanical wood pulp are added, belong to this group, the principal representathe contrast of shade being thus considerably tives of which are-iron buff, manganese reduced. The colouring matters used in the bronze, chrome yellow and orange, Prussian dyeing of paper pulp may be conveniently blue, ultramarine and smalts. divided into two groups, namely, the sub The other group of colours with which we stantive, and the adjective colours. The have to deal next are the organic colours. former dye fibres direct, that is without the They may be sub-divided into “natural application of a mordant, whilst, when the organic colours," that is colours of vegelatter are used a previous mordanting of the table and animal origin, and “ artificial fibres is necessary to ensure fixation.
colouring matters" usually called “coal tar In the manufacture of cheap coloured colours.” Many of the colours belonging to papers, the rosin size added to the pulp the former group have been superseded by the may be considered as the natural mordant for artificial products which are more easily many colours. The finely divided rosin, which appplied and which may be obtained in a surrounds the fibres, acts in these instances as more concentrated form. a fixing agent.
Of the natural organic colours, annatto, The mordants most commonly used in paper turmeric, safflower, red wood, cochineal, weld, dyeing are alum and aluminium sulphate. and others, are now, practically speaking, of Their application is very simple, and they historical interest only. Amongst such colours possess a remarkable affinity towards many as are still extensively used, are logwood, and colouring matters. Iron salts, such as ferrous in combination with it, fustic extract, for cheap sulphate, nitrate of iron, and acetate of iron blacks and greys ; also catechu or cutch for are used in the dyeing of greys, blacks, and fast browns or as a bottom or a mordant for other dark shades and in the manufacture of dyeing heavy shades with aniline colours. Prussian blue, a colour very much in demand The artificial organic colouring matters now for paper dyeing.
at the disposal of the paper-maker are very Tannic acid is a very valuable mordant; numerous. Their characteristics are brilliancy with iron mordants it produces useful greys, and purity of shade, strength, easy application, which may be conveniently used as a bottom and solubility in water. Fastness to light and for other colours. Tannic acid, employed air is, however, with few exceptions, not their either by itself or neutralised, or precipitated strong point. with tartar emetic, is the best fixing agent for Time will only permit me to mention the the basic aniline colours, such as magenta, chief representatives of the various classes. methylene blue, &c.
Of the yellows and oranges we have auramine, The principal colouring matters which are metanil yellow, naphthol yellow, orange II. and used in the dyeing of paper pulp may now be chrysoidine ; of the browns—Bismarck brown briefly reviewed, classifying them for this and vesuvine; of the blues--water blue, Victoria purpose into “inorganic" and “organic blue, and methylene blue; of the reds—the colours.” Of the former class, the natural, eosines, rhodamines, palatine scarlet, safframineral colours also called earth colours, are | nine, and magenta ; of the violets-methyl still very extensively used on account of their violet and crystal violet; of the greenscheapness and their property of acting both as | brilliant green and malachite green ; and of colouring and loading materials. The various the greys- the nigrosines. brands of iron ochre, the oxide red, caput The application of colours to the pulp is, mortuum, umber, sepia, green earth, mineral however, not restricted to coloured papers. black, China clay and pearl hardening, are Nearly all whites have to be produced by adding amongst the principal representatives of this small quantities of colours. The natural shade class.
of the bleached pulp is counteracted by a