US1891730A - Composition for and method of papermaking - Google Patents

Description

Patented Dec. 20, 1932 UNITED STATES PATENT OFFICE GEORGE A. RICHTER, F BERLIN, NEW HAMPSHIRE, ASSIGNOR TO BROWN COMPAR'Y, OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE COMPOSTTION FOR AND METHOD OF PAPERMAKING No Drawing.

Cellulose fiber as found in nature or as liberated from various raw cellulosic materials, such as wood, is composed of fibers of widely varying lengths, some being above and some below the average fiber length of the fiber as a whole. It has been my observa tion that the short fiber portion or fraction of a pulp, including the fiber fragments and collodial cellulose, carries most of the impurities present in the pulp. This observation may be readily made under the micro scope or when the longfiber portion or fraction is separated froma pulp, for this portion is much freer from specks and is of better color than the original pulp or the short fiber residue. The separated long fiber is accordingly an excellent raw material for the manufacture of high grade papers.

I have found that, while the long fiber portion or fraction of a pulp may have excellent papermaking qualities,.nevertheless, it is far more ditficult to gelatinize or hydrate itto papermaking slowness than the original pulp from which it has been separated. 1 The characteristic of difficult hydratability'associat-ed with the long fiber portion is quite undesirable from the papermakers standpoint, as it means that much more energy and a much longer beating period is necessary to condition the fiber for papermaking. \Vhile this trouble arises in the case of long fibers separated from pulps of various origins. it is especially serious in the case of a wood pulp refined to-high alpha cellulose content, such pulp being originally as diificultly hydratable as a high grade new rag stoelc In order to gelatinize the long fiber portion of such pulp to papermaking slowness, it is necessary to beat for such a long period that the length of the fibers is greatly reduced and a comparatively large amount of energy expended. Even though the desired gelatinization may be realized after a long-time beating, such excessive beating may resultin finished papers which have no better, or even less, strength and tear resistance than when the original pulp is used as a raw material, particularly when good sheet formation is desired. When pulp consisting 0 of selected or separated longfibers is being Application filed Hay25, 192$. erial No. 280,655.

marketed by a pulp mill as a papermaking raw material, not only are there these serious objections to meet, but also the objection that the beater capacity of the pa er mill may be insufiicient to handle pulp 0? this character and yet maintain the desired output of paper.

According to the present invention, the foregoing difiiculties may be overcome by mixing or blending with the separated long fiber portion or fraction before marketing it, gelatinized cellulose in sufiicient amount to render such fibers easily hydratable to papermaking slowness. This enhances the utility of separating or selecting the iong fibers from pulps of various types, including kraft pulp, sulphite pulp, and especially refined wood pulps, and using the separated long fibers in the manufacture of papers. By separating the long fibers from wood pulp refined to high alpha cellulose content, for instance, and then mixing with the separated long fibers sufiicient gelatinized cellulose to reduce materially the beating necessary for apermaking, it is possible to preserve the ength of the fibers to a large extent and to produce papers having characteristics similar to those of high grade rag papers.

The method of the present invention may be practised either at a pulp mill or at a aper mill. Let us assume, for instance, t at a pulpmaker wishes to market the long fiber portion of a refined wood pulp in a condition such that it will respond readily to hydration when used at the paper mill. In such case, the long fiber portion may be separated from the rest of the pulp and then mixed with gelatinized cellulose in sufiicient amount so that when the mixture is subsequently put into a beater engine and beaten, it will be found to acquire papermaking slowness quite readily and at the same time result in papers having the characteristics of high grade rag papers. The facility or readiness of hydra tion of the mixture depends on the amount of gelatinized cellulose mixed with the long fiber portion, and in some cases sufiicient gel may be mixed therewith to produce a composition which upon beating acquires papermaking.=:sl owness as readily as ordinary sulphite iilp. The mixture of long, refined 100 wood fiber and gelatinized wood pulp produced at the pulp mill maybe shipped in any suitable form, for instance in a wet, pressed condition or as baled drier sheets. If the mixture is being used for paper manufacture at the pulp mill, gelatinized cellulose may be added in sufiicient amount to the long fiber portion to slow it down sufficiently so that little beating of the mixture will be required.

One of the advantages of the method of the present invention is that the short fiber portion remaining after the long fibers have been separated therefrom may be used as the raw material for furnishing the gelatinized cellulose for mixin with the long fiber portion. The short fiber portion gelatinizes' very readily, bein initially quite slow, as it contains most of t e fiber fragments and colloidal cellulose associated with the originalpulp. By first separating the long fiber portion from a pulp, gelatimzing the remaining pulp, and mixing the gelatinized cellulose with the long fiber portion, it is possible to produce paper having much better characteristics than would result if the pulp as a whole 1 were beaten to the same slowness and made into paper. In other words,:the present invention makes possible the preservation to a large degree of the length of the long fibers of a pulp when making paper, the short fibers being used to furnish most or all the gel necessar for bonding the fibers of the paper toget er. hen papers of very high whiteness and permanence are desired it is preferable ytouse long refined fibers as the source of the gelatinized cellulose, the long fibers being relatively free from resins, specks, and other impurities which impart color to the fiber "and cause ylellowing under the action of heat, air a'ndlig t.

Anexample of procedure which may be followed at a pulp mill in producing a high grade papermaking composition suitable for marketing and which will hydrate to papermaking slowness quite readily, may be substantially as follows. The pulp produced as a raw material at the pulp mill may be a. wood fiber refined to high alpha cellulose content and to the whiteness of new cotton fiber. This pulp may be passed through apparatus I, such as described in patent ap lication Serial N0.'206,477, filed July 18. 192 by Robert A. Webber, (now Patent No. 1,786,973, issued December 30, 1930). An apparatus ofthis type serves to separate or divide the pulp into a longfiber portion and a short fiber portion. The long fiber portion may then be 'mixed with a relatively small amount of gelatinizedv cellulose, say about 6%, which may be. pre ared from either the short fibered portion or rom'long fibers. The gelatinized pulp is preferably prepared in heaters of the stone-rolltype, such as employed in the glass-, ine paper industry, as beaters of this general type yield better gels and may be operated more economically for this kind of work than the usual paper mill heaters. Preferably, the stock is cooled while being gelatinized, as described and claimed in patent application, fierial No. 224,427, filed October 6, 1927, as this makes possible more economical operation-and the production of high grade gels. The mixing or blending of the gel and the longI fibers may be conveniently carried out in t e usual beater engines, the gel and unbeaten fiber preferably being mixed at a conslstency of about 3% to 3 70, as under these conditions homogeneous mixing may be readily effected.

The following table gives the characteristics of the origmal pul the separated lon fiber, and the mix or b end of t e separate fiber and gel, after each had been beaten for a definite period of time.

6% el and Separated slowness Tear Fiber length (mm) 6-. 8 mm. 1. 3-1. 8 1.53:"

pc s g von we 0 pulp) '30 20 20 Breaking length is the length of paper which it freely suspended would break as result of its own weight.

It is impossible to ascertain accurately the avera e fiber length of the mixture owing to the (act that a port on of the ii r exists in the form 0! gal and fiber fragments.

The foregoing is representative of cases involving the use of a wood pulp refined to high alpha cellulose content as the raw ma; terial but this is illustrative of what happens to a greater or less degree with fibers of other origins. It is to be noted that by adding only about 6% gel to the separated long fiber, the mixture acquired a much greater slowness after a given period of heatmg than the original pulp or the separated long fiber and resulted 1n papers having reated strength, tear resistance, and breakmg length than the original pulp, even equalling the separated long fiber in these characteristics. The mixture also had a better color and a lowerspeck content than the original pulp, but were the gel prepared from the.

papers having high strength and tear resist ance, the length of the long "fibers havin been preserved to a large degree. One GOlllt not produce papers having such high tear resistance by beating the original pulp to the same degreeof slowness, for by so doing-the length of fiber of the pulp as a whole would be reduced to a greater degree, owing-to the much longer time of beating necessary. By beating a pulp mixture wherein the major portion exists as long unbeaten fiber, and a relatively small portion of which exists in highly gelatinized condition, the mixture as a whole need be beaten for a much shorter period to reach the desired apermaking slowness. In certa1ncases,'su olent gelat1- nized cellulose may be added to the unbeaten long fiber to eliminate the necessity of sub stantial beating of the mixture. That is to say, one may add sufficient gelatinized celludissemination of the gelatinized cellulose throughout the long fiber. This results in papers in which a very high proportion of the long fibers exist intheir original length, 3

the long fiber portion of cellulose pulp like pro-liberated wood pulp from the rest of the such papers having exceptionally high tear resistance: A I

' Having thus described certain embodimentsj of this invention,- it will be evident tothose skilledin the art that various changes and modifications might be made therein a only the separated and cleaner long fiber fraction of a cellulose pulp of the character A of pre-liberated wood pulp mixed with gelatinized cellulose.

2. A papermaking composition comprising only the unbeaten separated and cleaner long fiber fraction of cellulose pulp of the character of pre-liberated wood pulp mixed with gelatinized cellulose.

3. A papermaking com osition comprising only the unbeaten long fi r fraction of cellulose pulp of the character of pre-liberated wood pulp mixed with the gelatinized short fiber portion of the pulp.

4. papermaking composition comprisin unbeaten cellulose pulp of the character 0 pre-liberated wood pulp freed from its short fiber portion including fiber fragments and colloidal cellulose, and gelatinized similar ul p 5. A paperma'king composition comprising unbeaten wood pulp refined to high alpha cellulose content and freed from its short fiber ortion including fiber fragments and colloi' al cellulose, and gelatinized cellulose.

6. A papermaking composition comprising unbeaten wood fiber refined to high alpha cellulose content and freed from its short I fiber portion including fiber fragments and colloidal cellulose, and gelatinized pulp refined to high alpha cellulose content.

7. A papermaking composition comprising unbeaten wood fiber refined to high alpha cellulose content and freed from. its short fiber portion including fiber fragments and colloidal cellulose, and gelatinized similar pulp. y

8. A method which comprises removing the long fiber portion of cellulose pulp like pre-liberated wood pulp from the rest of the pulp, and mixing gelatinized cellulose with said removed portion.

9. A method which comprises removing the long fiber portion of cellulose pulp like pre-liberated wood pulp from the rest of the pulp, mixing gelatinized cellulose with said removed portion, and forming into paper.

10. A method which comprises removing the long fiber portion of cellulose pulp like pre-liberated wood pulp from the rest of the pulp, gelatinizing the rest of the pulp, and

mixin the gelatinized pulp with the removed long. her portion.

11. A method which comprises removing pulp, mixing gelatinized cellulose with said removed portion, beating the mixture, and forming into paper.

12. A method which comprises removing the long fiber portion of cellulose pulp like pre-liberated wood pulp from the rest of the pulp, and mixing gelatinized long fibers with the removed long fiber portion.

13. A papermaking composition comprising only the separated long fiber portion of a cellulose pulp mixed with mechanically gelatinized cellulose.

14. A method which comprises removing the long fiber portion of cellulose pulp from the rest of the pulp and mixing mechanically gelatinized cellulose with said removed portion.

In testimony whereof I have afiixed my sig-