US1983572A - Paper and process of and apparatus for making the same - Google Patents

Description

Dc. 11, 1934. N. s'rATHAM 'ET AL. 1,933,572

PAPER AND PROCESS OF AND APPARATUS FOR MAKING' THE SAME Filed March 8, 1953 14 PRg-c/P/ rn raf? scese/v NLP /19 FHRER/NIA?? -P u warm M. 50x55 www aka/re' 29 I I I causar/Ms Make' 36 DRY HMKE WATER wam/ER 26 werf/v rsAvL-ALLs p/f INVENTORS M BY .I M

ATTORNEY- raaniesnee. ii, 1934 PATENT orner.

rAraa AND PROCESS F AND APPARATUS FOR HEARING THE SAME Noell Statham, Irvington, N. Y., and Thomas G.

\ Leck, Covington, Va.,

assignors to industrial Chemical Sales Gompany, line., New York, N. Y., a corporation of New York' ApplicationMarch 8, i933, Serial No. 659,990

7 Claims.

This invention relates to an improved method of manufacturing paper and to an improved type of paper resulting from such method. More particularly it has to do with lthe production of a Si superior chalk-filled or coated paper, especially suited for printing or lithographie work. The product of the invention has a smooth, velvety nish which presents a better printing surface than any paper heretofore made. It has better l@ color than 'prior papers and is more readily capable of absorbing the pigment carriers employed in inks. This results in quicker drying and enables the printer to shorten the time required for printing, while at the same time a clean, clearlld out impression of the type is obtained. A further feature of the improved product is its increased bulk in proportion to its weight and this advantage is obtained Without decreasing the opacity of the paper. In fact the paper made in accord- 20 ance with this invention has greater opacity than any papers of equal Weight heretofore produced. Thus it may be stated that the improved process produces a paper having better printing quali-f ties, better color, greater opacity and more bulk 2.5 than papers of similar weight and character previously made.

While the'improved process is particularly advantageous in the production of a printing paper having a smooth, glossy finish, it may also be it@ used in the production of a high quality news able asthe result of the better absorption, as ap plied to krafttpaper or board as well as white paper, is the clear-cut orstraight-line effect produced in any printed manner. The inks or coloring matter permeate the paper or board quickly, without spreading. The absence of offsetting is another advantage noticeable in the paper producedfby the present method. Various I 50 other special products may be formed to advan- V- tage by the present invention. These may include, for example, highly absorbent paper toweling, shredded paper or pulp kused in the Jnanufacture of lmedical dressings, catamenial band- 55 ages, the like.

(Cl. S21-21) A primarylfea'ture of the present invention` is the addition tol a paper pulp of freshly formed, precipitated chalk in suspension in the liquid in which it is produced. The chalk may be added to the pulp prior to its formation into the sheet, in which case it is thoroughly intermixed with the entire mass of pulp, or it may merely be applied to thevskurface of a sheet already formed in a paper machine, preferably on the wire side, if not on both sides, orl it may be both mixed with the pulp and applied to the surface of the sheet.

Heretofore various pulverulent, substantially inert products have been added to pulp as a filler or as a coating or size in the production of paper for lithographie and printing purposes, other than newsprint paper. used to a considerable extent for this purpose and precipitated chalk has also been used to advantage. The addition of these nely divided substances serves to ll the interstices between the cellulose fibres so that a smooth surface, ,suitable for printing, is obtained. Filling of the interstices in this manner also tends to increase Vthe opacity of a sheet of given thickness. As heretofore employed .the inert substance has been obtained in a dry, powdered state and'has been first mixed with water to form a paste orliquid suspension and. this has been added to the pulp mass or to other sizing ingredients to be added to the surface of the' sheet. Now, We have discovered that fgreatly superior results may be obtained by the addition of a light precipitated chalk in the form in which it is originally produced and preferably when freshly produced. 'I'he addition of a given .quantity of chalk in this form results in the production of a. smoother and whiter finish, and gives to the paper a greater degree of opacity than can be produced even by the use of an equal amount of light precipitated chalk which has been dried and then niized with water. There is apparently a greater uniformity of distribution of the chalk particles through the liquid as it is formed than can be obtained by mixing the dry powdered chalk with water. The colloidal character of the product as rst formed is apparently more .perfect and better suited to its use as a ller. This is made apparent by the greater viscosity of the material when originally iproduced than when dried and repulped. The dried chalk appears to be more crystalline and has a tendencyto form coherent.

particles, thus increasing the size of the particles to be distributed through the pulp. There may be other explanations for the superiority of the chalk as formed over dry'chalk repulped and we Powdered china clay has been 30 to a suitable slaker or hydrator li.

do not intend to limit ourselves to any particular theory as to this. Y

The nature or the invention; and its other features and advantages, may be more'readily 5 understood by reference to the detailed descripg tion yci an illustrative mode of carrying out the invention now to be given in conjunction with the drawing which illustrates diagrammatically a suitable arrangement of apparatus that may iY be employed.

The equipment required tor the conduct of the process is suitable apparatus designated generally by theY letter A, for the production of light precpitated chalk and a paper machine oi any conl venient form, designated generally by the lett/er The 'equipment employed Ylor the formation oi. the chalk may be of any convenient form and may be operated under any suitable conditions which will result in the production of a nne, light,

precipitated product. Suitable apparatus for the purpose is disclosed in the patent to Statham, No. 1,266,339, granted May ld, 1918. It may comprise a lime kiln l0 adapted to receive successive charges of limestone and fuel, such as coke.n In

the consumption of the fuel it is converted largely and the screened liquid is passedninto a reaction vessel oriprecipitator 14.

The carbon dioxide which is developed in the lime kiln is also forced by means of a blower 15 into the'top of the precipitator. By the` means .10 disclosed in my prior patent, the milk of lime may be sprayed or agitated, or both, within the precipitator to bring it into intimate contact with the carbon dioxide. The resulting reaction will bring about the precipitation oi fine particles of chalk. rIhe precipitator may be maintained during the reaction under substantially atmospheric pressure or, if desired, under a suitable superatmospheric pressure of between, say, 20 and 100 pounds. The operating conditions may be suitably varied to tit the particular requirements.

Preferably, the conditions will be so regulated as to bring about the production of as light and f ne a chalk as possible. It will be understood that if desired the material undergoing reaction ln the precipitator may be continuously circulated ln the manner explained in the said Statham patent. Several precipitators may be employed ln series, if desired'.

When the carbonationof the milkof lime has been completed or carried to the desired point,

the mixture of chalk and water is withdrawn from the precipitator and passed to a. screen 18. The chalk slurry which passes through the screen may then be delivered directly to some convenient portion oi the paper-making apparatus B where it will be thoroughly mixed with the pulp libres. It will be understood that throughout the apparatus there will be provided suitable pumps, valves, and other handling and control devices,

known in the art, for transferring the various materials from one point to another.

The paper-making equipment may be of any conventional form. Pulp which has been previously digested and washed'may be introduced through aline 19 into beaters 20. The chalk slurry Leonora may also be advantageously introduced into the beaters since they afford an excellent-opportunity for thorough intermingling of the chal/k and fibres. The stock used in the beater may include a certain amount of old stock, such as old magazines and the like, repulped. A suitablesizing mixture may be added to the material in the beaters. IrI'his may, for example, be a rosin size, in which case a dilute sulphuric acid solution will preferably be added at a later stage, as in the flow box to be described hereinafter, for'the purpose or" assisting inthe setting oi the size. The presence of the size, obtained from' the old stock or separately introduced, seems to assist in the colloidal suspension of the chalk and therefore improves the distribution olthe chalk through the nbres. Upon completion of the beating operation the mixture may be passed to a beater chest 2l. This product may then be subjected to refinement in any suitable way, as by treatment in Jordans, indicated bythe reference numeral 22. After refinement the pulp is passed to a machine chest 23. If desired the chalk slurry might be introduced at this point in lieu of going to the beaters. The mixture of the chalk and pulp, at the appropriate concentration for proper handling by a paper making machine, say between l and 2%, is then' passed to" the mixing box or flow-box 24 of such a machine.` This portion of the equipment ymay be of any conventional form and need not be described-in detail. As will be understood, the pulp delivered to the flow-boxis spread over a wire screen or cloth forming an endless conveyor in a Fourdrinier portion 25 of the machine. Water which drains through the wire mesh is collected and utilized in variousways. 'I'hefshower is preferably collected in a'jpit 25 and then passed to saveaus 27. l Y

It will be found that the water accumulated in the save-alls 27 may be used to advantage in the slaking of the lime. Forthis purpose a portionof the save-all water may be passed through a line 28 to the slaker 11. In this way the chalk content of this water will be saved and other ingredients such as sizing substances, ne fibrous particles and the like, will assist in the formation of an excellent colloidal suspension. Excess water accumulated in the save-alle may be utilized inany convenient manner as in the washing of the pulp, and the like.

A portion of the water which' is withdra from the pulp on the wire screen and collected in the save-all pans, suction boxes, suction couch, and the like, may be returned through a lime 29 to the mixing box. Any wet broke which may bel developed maybepassed to a collecting pit 30 and after repulping may be returned to the beaters. The sheet of matted fibres formed on the screen may next be passed through sets of presser Vrollers 31 which serve to squeeze more of the water from the material. This water may be used to advantage in the pit 30 for the repulping of the wet broke. f

In lieu of usinga settling tank as a save-all, an automatic continuous llter may be used. This is made desirable 'by the presence of the fine chalk J If desired asmall quantity of lime`may be added' greater amounts may be masacre to the white water removed from the'l pulp on the machine to' bring aboutv rapid settling of the ller and iibre. In this case it will be desirable to agitate the settled slurry with carbon dioxide gas to carbonate whatever free lime may be included in the slurry before returning this to the beaters or machine chest. 'Ihe clear lwater from which the slurry has been removed should preferably also be broughtI into intimate contact with carbon dioxide in a suitable tower to carbonate the lime in solution prior to the use of this water for washing the pulp and the like. The carbon dioxide for this purpose may be obtained from the absorber or precipitator 14, since a considerable excess over that required at this point is developed in the kiln. Due to the reaction between alum and lime it will be undesirable to add lime in the manner indicated if any alum size should be present.

Upon leaving the presses 31 the partially dry web is passed between a series of drying rolls forming dryers 32 and then between calender rolls 3.3 and finishing rolls 34. The nished product, indicated by the arrow 35, may be passed to suitable winding equipment or may be taken care oi in any other convenient manner for shipment or storage. Should the web of paper become'torn in its passage through the machine, or upon leaving it, the portion which is destroyed may be passed to a broke beater 36 in which it isy repulped, by utilizing some of the shower-pit water, for @X- ample, and then, through the line 37, it may be passed to the beaters 20.

It will be apparent that in addition to the improvement in the product resulting from the use of freshly formed wet chalk, certainbenets are derived from the fact that the chalk producing system and the paper making equipment are brought together and operated in a closed cycle. An economy is effected by the return oi the waste products of one portion of the system to a point where the Valuable ingredients mayV be recovered and utilized to advantage. The quantity of chalk added to the pulp may be varied to suit the particular requirements. Beneficial results may be obtained from the addition of only small quantities. Generally it will be found advantageous to add sumclent chalk to i'orm between 10 and 30% of the weight-or the resulting paper. Due to the extreme finenessand even distribution of the wet chalk, however, even used, if desired At the same time a given quantity of chalk, added in accordance with this invention, will produce even better results than a chalk slurry iormedirom dry chalk. This may be illustrated by comparison of papers actually formed under substantially similar conditions from dry chalk re-puiped and from the wet chalk freshly formed. Paper produced by the use of dry chalk re-pulped was found to weigh 1.4.95 lbs. per ream, left an ash residue (Cao) of 15% and had an opacity or 73.2%. This is as measured byL opacimeter employing a photo-electric cell associated with a micro-ammeter; the paper tested is placed between a source of light and the cell and the degree or opacity lis indicated. on the ammeter. A similar grade oil paper produced by the use of frhly formed wet chalk had a weight o 44.1, leitan ash 'residue of 14.3% and had an opacity of 795%. Therefore, while the ash content indicates that there was actually less chalk in the wet chalk product, it

- had greater opacity. This would seemto show a more perfect, even distribution of the chalk particles when applied in the freshly formed, wet state. By .way Vof comparison, it may he nien= tioned that a clay lled paper weighing 44.6 lbs. per ream and leaving 24.5% ash .upon ignition,

substantially equivalent to the chalk papers above c. c. of water and allowed to stand for a periodv of 24 hours Vshowed a bulk of 40 c. c. In one hour it had settled to 50 c. c. and in two hours it had settled to 45 c. c. A quantity of the wet chalk containing l0 grams of the solid particles, mixed with suiiicient water to form 100 c. c. showed abulk at the end of 24 hours of 60 c. c. It had settled only to 90 c. c. in one hour and 80 c. c. in two hours. The figures mentioned in each case represent the averages of three tests. This affords e furtherexplanation 'for the superiority of the wei chalk product. I

A further indication of the greater iineness and more even distribution of the undried particles is given by a viscosity test. It was found from a series of tests that 50 c. c. of a slurry of the undried chalk required an average of 73,5 seconds to empty from a standard 50 c. c. burette. Similar tests upon a slurry formed from dry chalk,

lhaving the same concentration, containingA 8.9

grams per 50 c. c. of the liquid suspension, showed anv average of 6l seconds required to empty the burette. The foregoing result is vmorestartling when it is considered that in a grit and agglomeration test the undried chalk showed a great deal less residue than the dried chalk. One wouldgv naturally .expect the agglomerated particles to interfere more with the discharge of the suspension from a burette but, in fact, the more even distribution of, the wet chalk particlesincreased the viscosity of the liquid suspension to such an extent that a greater interference With the dow was produced. Ihe residue in washing 56.2 c. c. of the wet chalk slurry through a? 200 mesh screen was only .1% while' a similar slurry containing lo vgrams of dry chalk left a residue of .335% on a 200 mesh screen. ln each case all but a trace of the residue was soluble in hydrochloric acid.

Various other tests have been conducted by way of comparison of the paper produced in accordancewith the present improved process and paper having other fillers, such asdried chalk, clay and other known substances. These tests clearly Vshow greater opacity resulting from the use of freshly formed, wet chalk than from the use of a like quantity of other fillers, such as clay and dried chalk. They further indicate that a prod; uct of greater bulk for a given weight is vproduced by the present process. That the improved paper is of lower density is demonstrated by the `more rapid leakage of air through the paper when a pressure differential is maintained on the two sides. The advantage of the new paper with respect to rapid absorption and drying of ink during a printing operation is demonstrated by a penetration test. A mixture of 50% oil and 50% water is round to penetrate considerably more quickly through the improved, wet-chalk paper than through other filled papers of similar character. A marked improvementv in the color o the/paper resulting from the use of the present ,process may be noted. Paper containing the wet chalk ller is noticeably whiter than other papers produced from. the same kindof stock and printing imprese sions `on the new paper are clearer, sharper, and

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