A TEXT-BOOK OF PAPER-MAKING; by C. F. CROSS AND E. J. BEVAN (1888)
| Cotton. × 50. | Linen. × 50. |
| Esparto. × 50. | |
| Mechanical Wood-pulp. × 50. | Chemical Wood-pulp. × 50. |
A
TEXT-BOOK OF
PAPER-MAKING.
BY
C. F. CROSS AND E. J. BEVAN.
E. & F. N. SPON, 125, STRAND, LONDON.
NEW YORK: 35, MURRAY STREET.
1888.
PREFACE.
The practical portion of the present work has in part already appeared as an article, by one of the authors, in ‘Spons’ Encyclopædia of the Industrial Arts.’ Since its publication, however, many and important improvements have been introduced in this, as in other branches of the art of paper-making, which necessitated considerable additions to the original article. It has at the same time been to a great extent re-written, and, as the authors hope, improved.
Our object in writing this book has been to bring before students and others the principles upon which scientific paper-making should be conducted, a concise exposition of which has not, we believe, been hitherto attempted.
Considerable prominence has been given to this aspect of the subject, possibly at the expense of what some may consider more essential details.
A belief in the importance of a thorough scientific training for paper-makers has dictated the style and purpose of the book.
We have not thought it necessary to enter into minute details respecting the construction of machinery, &c.; for these the reader is referred to such works as Hofmann’s Treatise on the Manufacture of Paper.
Much of the scientific portion is here published for the first time. Part of it has already appeared in the form of papers read before various societies.
The chapter relating to the Treatment of Wood formed the subject of an essay, which obtained the prize offered by the Scottish Paper-makers’ Association, in connection with the Edinburgh Forestry Exhibition, 1884.
We would here express our obligations to Messrs. G. and W. Bertram, Messrs. Masson, Scott, and Bertram, Messrs. Rœckner and Co., and others, for their courtesy in furnishing us with the drawings from which the illustrations were prepared; to Dr. C. R. A. Wright, F.R.S., who kindly communicated the substance of the chapter on the Action of Cuprammonium on Cellulose; to Mr. Carl Christensen, for drawings and information regarding the manufacture of mechanical wood-pulp; also to the following friends, among others, who have, in various ways, rendered us important assistance:—Messrs. R. C. Menzies, C. M. King, G. E. Davis, A. Beckwith, and C. Beadle.
Finally, we would tender our thanks to Mr. C. G. Warnford Lock for the care he has bestowed on the editing of the book. The indexing and the Chapter on Statistics are entirely his production.
C. F. CROSS and E. J. BEVAN.
4, NEW COURT, LINCOLN’S-INN, W.C.
| CONTENTS. | |
|---|---|
| INTRODUCTORY NOTE | [1] |
| CHAPTER I. CELLULOSE—THE CHEMICAL PROPERTIES OF TYPICAL MEMBERS OF THE CELLULOSE GROUP, WITH REFERENCE TO THEIR NATURAL HISTORY | [4] |
| CHAPTER II. PHYSICAL STRUCTURE OF FIBRES—MICROSCOPICAL EXAMINATION | [30] |
| CHAPTER III. CHEMICAL ANALYSIS OF PLANT SUBSTANCES | [42] |
| CHAPTER IV. AN ACCOUNT OF THE CHEMICAL AND PHYSICAL CHARACTERISTICS OF THE PRINCIPAL RAW MATERIALS | [46] |
| CHAPTER V. PROCESSES FOR ISOLATING CELLULOSE FROM PLANT SUBSTANCES | [62] |
| CHAPTER VI. SPECIAL TREATMENT OF VARIOUS FIBRES—BOILERS, BOILING PROCESSES, &C. | [79] |
| CHAPTER VII. BLEACHING | [110] |
| CHAPTER VIII. BEATING | [117] |
| CHAPTER IX. LOADING, SIZING, COLOURING, &C. | [127] |
| CHAPTER X. PAPER MACHINES, HAND-MADE PAPER | [144] |
| CHAPTER XI. CALENDERING, CUTTING, &C. | [167] |
| CHAPTER XII. CAUSTIC SODA, RECOVERED SODA, &C. | [177] |
| CHAPTER XIII. THE TESTING OF PAPER, MECHANICAL, CHEMICAL, AND MICROSCOPICAL | [193] |
| CHAPTER XIV. GENERAL CHEMICAL ANALYSIS FOR PAPER-MAKERS | [205] |
| CHAPTER XV. SITE FOR PAPER-MILL—WATER PURIFICATION | [210] |
| CHAPTER XVI. ACTION OF CUPRAMMONIUM ON CELLULOSE—WILLESDEN PAPER | [217] |
| CHAPTER XVII. STATISTICS | [221] |
| CHAPTER XVIII. BIBLIOGRAPHY | [229] |
| CHAPTER XIX. ADDENDA | [231] |
| INDEX | [233] |
{1}
PAPER-MAKING.
INTRODUCTORY NOTE.
The raw materials of the paper-maker are primarily the vegetable fibrous substances; in addition to these there are various articles which are employed as auxiliaries, either in the preparatory or finishing processes to which these fibrous materials, or the web of paper are subjected. The latter class are of subsidiary importance, more especially from our present point of view.
In insisting upon the recognition of first principles, we cannot overrate the importance of a thorough grasp of the constitution of the plant fibres, as the necessary foundation for the intelligent conduct of paper-making, and to this subject we will at once proceed.
Careful study of a mature plant will show that it is made up of structural elements of two kinds, viz. fibres and cells, which, to use a rough parallel, we may liken in function to the bricks and mortar of a house. It is the former which admit of the many extended uses, with which we are familiar, in the arts of spinning and weaving, and which constitute the fabrics which are the most indispensable to our civilised life. For the most part, as we know, fibres and cells are aggregated together into compound tissues, and a process of separation is therefore a necessary preliminary to the utilisation of the former. The cotton fibre is the only important exception to this general condition of distribution. Here we have the seed envelope or perisperm, converted into a mass {2} of fibres, and these by a spontaneous process accompanying the ripening, so isolated as to be immediately available. Next in order in point of simplicity of isolation, are those fibrous masses, or tissues, which, although components of complex structures, exhibit a greater cohesion of their constituent fibres than adhesion to the contiguous cellular tissues with which they go to build up the plant. Into such a tissue the “bast,” or inner bark layer of shrubs and trees, more especially those of tropical and sub-tropical regions, frequently develops, and it is, in fact, this bast tissue, graduating in respect of cohesion of its constituent fibres, from a close network such as we have spoken of, to a collection of individual fibres or fibre-bundles disposed in parallel series, which supplies the greater part of the more valuable of the textile and paper-making fibres; we may instance flax, hemp, and jute, each of which is the basis of an enormous industry. According to the degree of adhesion of the bast to the contiguous tissues, or, in another aspect, according to its lesser aggregate development, so is the difficulty of isolation and the necessity of using processes auxiliary to the mechanical separation of the tissue.
It is worthy of note here that the Japanese paper with which we are in these times so familiar, is prepared by the most primitive means from the bast of a mulberry (Broussonetia papyrifera); the isolated tissue, consisting of a close network of fibres, is simply cut and hammered to produce a surface of the requisite evenness, and the production of a web of paper is complete. In isolating the bast fibres employed in the textile industries, a preliminary partial disintegration of the plant stem is brought about by the process of steeping or retting, by which the separation of fibre from flesh or cellular tissue is much facilitated.
Last in order of simplicity of distribution, we have the fibres known to the botanist as the fibro-vascular bundles of leaves and monocotyledonous stems, these bundles being irregularly distributed through the main cellular mass, and consequently, by reason of adhesion thereto, much more {3} difficult of isolation. For this and other reasons, more or less in correlation with natural function, we shall find this class of raw material lowest in value to the paper-maker.
It is necessary at this stage to point out that the work of the paper-maker and that of the textile manufacturer are complementary one to the other, and the supply of fibrous raw material is correspondingly divided: it may be said, indeed, that the paper industry subsists upon the rejecta of the textile manufactures. The working up of discontinuous fibre elements into thread, which is the purpose of the complicated operations of the spinner, is conditioned by the length and strength of these ultimate fibres. Paper-making, on the other hand, requires that the raw material shall be previously reduced to the condition of minute subdivision of the constituent fibres, and therefore can avail itself of fibrous raw material altogether valueless to the spinner, and of textile materials which from any cause have become of no value as such. To the raw materials of the paper-maker, which we have briefly outlined above, we must therefore add, as a supplementary class, textiles of all kinds, such as rags, rope, and thread.
Having thus acquired a general idea of the sources of our raw materials, we must study more closely the substances themselves, and first of all we must investigate them as we should any other chemical substance, i.e. we must get to understand the nature and properties of the matter of which the vegetable fibres are composed. While these exhibit certain variations, which are considerable, the substances present a sufficient chemical uniformity to warrant their being designated under a class name: this name is cellulose. The prototype of the celluloses is the cotton fibre.
{4}
CHAPTER I. CELLULOSE: THE CHEMICAL PROPERTIES OF TYPICAL MEMBERS OF THE CELLULOSE GROUP, WITH REFERENCE TO THEIR NATURAL HISTORY.
Plants are so far built up of cellulose that it may be called the material basis of the vegetable world. Plant tissues, however, seldom, if ever, consist of pure cellulose, but contain besides, other products of growth either chemically combined with the cellulose or mechanically bound up with the tissue, which are, according to the nature of their union, removable either by means of fundamental chemical resolution or by the application of simple solvents. A general method for the isolation of cellulose consists in exposing the moist tissue to the action of chlorine gas or of bromine water in the cold, and subsequently boiling in dilute ammonia; repeating this treatment until the alkaline solution no longer dissolves anything from the tissue or fibre. The cellulose is then washed with water, alcohol, and ether, and dried. Obtained in this way, or in the form of bleached cotton, or of Swedish filter paper, it is a white substance, more or less opaque, retaining the microscopic features of the tissue or fibre from which it has been isolated. Its sp. gr. is 1·25–1·45. Its elementary composition is expressed by the percentage numbers (Schulze)
| C | 44·0 | 44·2 |
| H | 6·3 | 6·4 |
| O | 49·7 | 49·4 |
or by the corresponding empirical formula, viz. C6H10O5.
These numbers represent the composition of the ash-free cellulose. Nearly all celluloses contain a certain proportion, {5} however small, of mineral constituents, and the union of these with the organic portion of the fibre or tissue is of such a nature that the ash left on ignition preserves the form of the original. It is only in the growing point of certain young shoots that the cellulose tissue is free from mineral constituents. (Hofmeister.)
As already indicated, cellulose is insoluble in all simple solvents; it is, however, dissolved by certain reagents, but only by virtue of a preceding chemical modification. An exception to this is to be found, perhaps, in the ammoniacal solution of cupric oxide (Schweitzer’s reagent), in which it dissolves without essential modification, being recovered by precipitation, in a form which is chemically identical with the original, though differing, of course, in being structureless, or amorphous. This reagent may be employed in a variety of forms, but the following method of using it is to be recommended as the most certain in its results. The substance to be operated upon is intimately mixed with copper turnings in a tube which is narrowed below and provided with a stopcock. Strong ammonia is poured upon the contents of the tube and, after being allowed to stand for some minutes, is drawn off and returned to the tube; the operation is several times repeated until the solution of the substance is effected. In order to facilitate the oxidation of the copper by the atmospheric oxygen, a current of air may be aspirated through the apparatus. The solution of the oxide prepared in this way is more effective in its action on cellulose than that obtained by dissolving the precipitated hydrate in ammonia. Cellulosic tissues in contact with this reagent are seen to undergo a disaggregation of their fibres, which swell up, become gelatinous, and disappear in solution. On adding an acid to the viscous solution, a precipitate of the amorphous cellulose is obtained in the form of a jelly resembling hydrated alumina; after washing and drying, it forms a brownish, brittle, horny mass. The cellulose is also precipitated upon simply diluting the viscous solution with water and allowing it to stand {6} 8–10 days in a closed vessel. From this observation it was inferred by Erdmann that the cellulose could not be considered as dissolved in the strict sense of the word, but the experiments of Cramer upon the osmotic properties of the solution proved this inference to be unfounded, and that cellulose is actually dissolved by the ammoniacal solution of copper oxide.
On treating the ammonio-cupric solution of cellulose with metallic zinc, this metal precipitates the copper, replacing it in the solution, and producing the corresponding ammonio-zincic solution of cellulose, which is colourless. Some of these solutions are lævo-gyrate.
Cellulose, in those forms to which the application of the term has been hitherto restricted, is a comparatively inert substance, and its reactions are consequently few. One of these is available for the identification of cellulose, and is chiefly used in the microscopical examinations of tissues: this is its reaction with iodine. Cellulose is not coloured blue by a solution of iodine excepting under the simultaneous influence of hydriodic acid, potassium iodide, sulphuric acid, phosphoric acid, or zinc iodide or chloride. The solution is prepared in the following way: zinc is dissolved to saturation in hydrochloric acid, and the solution is evaporated to sp. gr. 2·0; to 90 parts of this solution are added 6 parts potassium iodide dissolved in 10 parts of water; and in this solution iodine is dissolved to saturation. By this solution cellulose is coloured instantly a deep-blue or violet. For the identification of cellulose in the gross, mere inspection is usually sufficient; confirmatory evidence is afforded by an observation of the action of the ammonio-copper reagent, and of the absence of reaction with chlorine water. (See p. [18].)
Cellulose in its earlier stages of elaboration has no action upon light; but with age it acquires the property of double refraction, not, as has been shown by experiment, by virtue of its state of aggregation, but of its molecular constitution (Sachs). {7}