US2008142A - Paper and method of making - Google Patents

Description

y 1935- J. L. M CLELLAN 2,008,142

PAPER AND METHOD. OF MAKING Filed May is, 1932 hum/70,2

I L/W/IIZ Wf/ ,4/1 wwwm mercerization of the fiber. Consequently, such preheated solution of sodium hydroxide of 17 Patented- July 16, 1935 Q UNITED STATES PATENT OFFICE 2,008,142 PAPER AND METHOD OF MAKING James L. llTClellan, Littleton, Mass., 'assignor to Hollingsworth & Vose Company, Boston, Mass a corporation of Massachusetts 1 Application May 16, 1932, Serial No. 611,573

12 Claims. (CI. 92-13) This invention relates to a method for the preptreatment does not amount to more than a puriaration of paper pulp and for the production of flcation treatment of the cellulose fibers. a porous, open fibrous sheet of paper therefrom. It is an object of the present invention to pro,-

It has heretofore been proposed in the art to vide a more convenient and also a more reliable 5 treat a sheet of paper or porous web composed process for the preparation of fibrous pulp, in 5 l of wood pulp, kraft, sulfate, or like cellulose which the fibers are mercerized'but may or may fibrous materials generally by immersing the not be curled, as hereinafter described, and which sheet in a caustic soda solution having a concenmay be made into a porous sheet of open formatration of 20% to 25% sodium hydroxide for 9, tion. The fibers or fibrous material may be devery brief interval, followed by drying and washrived from wood fiber pulp, such as kraft pulp,

ing the dried sheet with a. neutralizing bath of manila rope, or cotton fibers, or from mixtures sulfuric acid. Such treatment is effective to swell of such fibers. It is also an object to provide the fibers of the sheet, and the final product is a treated fibrous material in the form of a puriporous and of open texture somewhat resembling fied pulp which may be subsequently made into 5 felt. Such procedure is, however, diflicult in paper of the desired properties having an open practice and tends to disrupt the sheet owing to porous structure which renders it not only soft the necessity of excessive handling when wet. but readily and completely absorptive of impreg- Moreover, it also presents great difilculty by any hating materials, which may be of comparatively reasonably practical treatment in obtaining a high viscosity such as rubber latex. Other obsufficiently washed sheet to be free of the caustic jects will appear from the following disclosure. 20 soda or sulfuric acid used. In the event that The process of the present invention includes any of these reagents is left in the sheet, it the preliminary preparation of the sulfate, cottends to disintegrate and destroy the final prodton, or true hemp (such as manila) fibers, either not during storage and subsequent use. in the form of a pulp or in the form of laps, in

It has also been proposed to treat a preformed accordance with the usual procedures. The fiber 25 porous sheet of paper, containing a mixture of as thus obtained is immersed and dispersed in a cotton linters or other cellulose fibers which have caustic treating solution of mercerizing strength been given a preliminary caustic cook, with simi- (preferably previously heated to a temperature lar uncooked fibers such as cottonlinters, kraft, somewhat short of the boiling point) which conjute, etc. The treatment is said to be conducted tains sodium hydroxide in a concentration of ap- 30 with a caustic solution definitely controlled as to proximately 12% to 15%, as represented by a concentration and temperature within the limits Baum value of 15 to 20 Baum. The ratio of of 1% to 10% sodium hydroxide (in the initial solution to fiber may be varied, but is preferably treatment of the cooked linters), and between relatively low, andthe fibers are preferably uni- 8% and 18% sodium hydroxide in the final treatformly dispersed throughout the solution. The 35 ment of the paper sheet made therefrom, at. a mixture is then agitated without further heating temperature between 0 and 104 C. The fibers for several hours, whereupon the charge (espein t resulting product are said to be curled and cially when the proportion of solution is low) aspuff d o as to pr du a hig y'porous paper sumes adry, crumbly condition somewhat resem- 40 sheet or web. Such pr edure s, however. subbling corn meal. It is then dumped and washed 4e J'e t the S difiieulties as the foregoing D 'O completely free of reagents and may be diluted ess with respect to a dl a so to e Sa e with water to any concentration desired and run liability of retaining deleterious reagents in the i t th form of h t on a paper machine in fi d product in Spite of Continued Washingcordance with the usual practice of the art.

It has further been proposed to tr paper A specific instance of the practical applica- 45 Scrap With a caustic Soda Solution of Beum tion of the invention will be described with ref- (app y 5 NaOH? followed y Wa erence to the accompanying drawing, in which: s and making n a sheetuof p p r r paste- Fig. 1 is a diagrammatic side elevation of the board which is coated on one side and shellaced apparatus employed in preparing the pulp; and

on the other for the manufacture of stereotype Fig. 2 is a similar view of the paper making 50 matrices and the like. But it will be observed machinery. that in such procedures the concentration of the Referring to the drawing, the pulp, which may sodium hydroxide treating solution is relatively be the usual sulfate or kraft pulp, is charged low,-appreciably below that necessary to efiect in the rotary boiler l, which already contains a Baum, for example, heated to a temperature of 180 F. The ratio of pulp to caustic solution may be such as to provide 1 to 2 pounds of sodium hydroxide for each pound of' pulp. The drum is then closed and rotated for a period of 4 to 5 hours, the temperature being allowed to drop as a natural result of loss of heat to the surrounding atmosphere.

The treated charge is then dumped into the stock box 2 by inverting the boiler and opening the manhole 3. At this stage the charge is apparently free from excess of solution, and, as above suggested, resembles in its consistency a batch of wet corn meal. It is next dumped into the beating engine 4 into which fresh water is introduced through decline 5 and the reagent solution separated from the pulp by withdrawal through the rotating washer or screen 5. The washed pulp is then transferred to the stuff chest 7 in which it is agitated and diluted to a sumcient fluidity to be withdrawn by the pump 8 and delivered to the regulating tank 9 where its consistency may be further checked and controlled by the addition of water by the inlet pipe ii if necessary. The pulp is then passed to the Jordan 52 and thence into the stuff chest i3 which is provided with an agitator (not shown) to make and keep the pulp uniform.

The pulp as thus prepared may be delivered to the head box 14 (Fig. 2) where it is diluted with additional quantities of water from the inlet pipe l5 and thence is run into vat i6. From here it is taken up on cylinder H, in the usual way, in the form of a sheet which is transferred to the wet felt iii.

The sheet of paper thus formed is carried by the wet felt, supported by rolls 2 i, 22, 23 over suction roll 25, and thence to a carrying felt 25 supported by rolls 26 which convey the sheet to a series of drier rolls 21, 28, supported by conveyor belt 29 and thence to calender stack 3|, if de-' sired, from which the sheet is drawn bytake-up roll 32.

In accordance with this procedure, the pulp is not only given an intimate and definitely controllable mercerizing treatment with respect to its individual fibers, but is also completely free from reaction by-products and from excess of the reagent materials used, before it is formed into a paper sheet. It accordingly does not tend to retain the reagent materials used, as a sheet of paper does, and hence provides a purer fibrous product. The pulp as thus treated is, moreover, found to be entirely suitable for sheeting out into paper in the usual way and to produce a finished sheet which is not only characterized by the desired curly, wool-like structure of the individual fibers but also by a very porous open felt-like sheet structure. This renders it especially suitable for purposes in which. such papers are required to be subsequently impregnated, as by rubber solutions, latex, or the like.

The present treatment is characterized by being applied to the fibrous material in dispersed permits them to curl freely under the action of the caustic. The initial, relatively high temperature of the reagent solution assures complete wetting, admixture, and reaction by the caustic upon the mass of fibers, while the subsequent cooling checks such reaction gradually, thus preventing material. weakening and disintegration of the fiber substance. The final and rapid washing out of the reagent still further checks and overcomes continued action,the brief time interval and low temperature of the same preventing appre ciable swelling of the fibers which would otherwise occur. At the same time the introduction of other reagents such as sulfuric acid is avoided, and when the caustic has been washed out, the fiber pulp is substantially clean and in open,

curly condition and not of a gelatinous condition or individually swelled. At the same time, the treated fibers are competent to form a paper sheet according to the usual paper making practices which is open, free, relatively strong, free from impurities, and admirably adapted for such operations as require an open, easily penetrated structure, as for impregnation, absorption, and like functions.

It may be especially noted that the kraft or cotton fibers in the above treatment'are mercerized and also rendered curly thereby. With manila rope fibers, however, and the other true hemp fibers, (i, e. excluding common hemp) it is found that the fibers are not curled by the treatment but remain as substantially straight, rod-like fibers. Both types of treated fibers are, nevertheless, susceptible of being felted into a porous, open sheet, and are especially to be desired for the purpose of subsequent impregnation.. In such cases where the impregnated fibrous material is to be thereby bonded together, the inherently high fiber strength of the manila hemp is rendered effective, and the finished sheet is exceptionally strong and otherwise constitutes an especially valuable commercial product. Likewise, the kraft or cotton pulp (particularly when long-fibered) which forms an open, porous fibrous sheet, may be readily impregnated with fluids and the like. .When such impregnation also serves to bond the fibers together, they constitute a tough sheet in which the initial fiber strength, though lower than-that of manila or hemp fibers, is relatively high and is supplemented by the curly, entangled relationship of the fiber components.

I claim:

1. Method of preparing paper pulp, containing cotton, hemp, kraft or sulfate fibers, comprising the steps of mixing the same with a caustic solution of mercerizing concentration at a temperature of approximately F., agitating the mixture while causing the temperature of the same to drop gradually, and washing the fiber substantially free from soluble reagents and byproducts.

2. Method of preparing paper pulp, containing true hemp fibers, comprising the steps of mixing the same with a caustic solution of mercerizing concentration at a temperature of aping the same with a caustic solution of mercer-.

izing concentration at a temperature of approximately 180 F., agitating the mixture while cansing the temperature of the same to drop grad ually, and washing the fiber substantially free from soluble reagents and lay-products.

4. Method of preparing paper pulp, including cotton, hemp, krait or sulfate fibers, comprising "the steps of mixing the same with a caustic solution of mercerizing concentration at a temperature of approximately 180 F., agitating the mixture while causing the temperature of the same to drop gradually, washing the fiber substantially free from soluble reagents and byproducts, and thereafter diluting the pulp and running the same into theiorm of paper sheets.

5. Method of preparing paper pulp, including true hemp fibers, comprising the steps of mixing the'same with a caustic solution of mercerizing concentration at a temperature of approximately 180 F., agitating the mixture while causing the temperature or the same to drop gradually, washing the fiber substantially free from soluble reagents and by-products, and thereafter diluting the pulp and running the same into the form of paper sheets.

6. Method of preparing paper pulp, including manila fibers, comprising the steps of mixing the same with a caustic solution or mercerizing concentration at a temperature of approximately 180 F., agitating the mixture while causing-the temperature of the -same to drop gradually,

washing the fiber substantially free from soluble reagents and by-product's; and thereafter diluting the pulp and running the same into .the'

form of paper sheets.

'7. Method of prepari'ng'paper pulp, including after-diluting the pulp and running the same into the iormot paper sheets.

8;.-Method of preparing paper pulp, including cotton, hemp -kratt or sulfate fibers, comprising the steps of mixing the same with a caustic solution 01 mercerizing concentratiombetween 12% and 15% NaOH at a temperature of approxia mately 180 F., agitating the mixture while causing the temperature of the same to drop gradually, washing the flber substantially free from soluble reagents and by-products, and thereafter diluting the pulp and running the same into 10. Method of preparing paper pulp, includ ing cotton, hemp, krait or sulfate fibers, comprising the steps of mixing the same with a caustic solution of mercerizing concentration at a temperature of approximately 180 F., agitating the mixture, cooling and washing the fiber substantially free from soluble reagents and' by-products, diluting the pulp, and running the same into'the form of paper sheets.

11. Method of preparing paper pulp, includ-- ing cotton, hemp, kraft or sulfate fibers, comprising the steps oi' mixing the same with a sodium hydroxide solution of mercerizingconcentration at a temperature of approximately 180 F., in approximately the proportions of two pounds of dry pulp to one to two pounds of sodium hydroxide, while causing the temperature of the sametodrop gradually, and washing the fiber, substantially free from soluble reagents and by-products.

12. Method of preparing paper pulp, including cotton, hemp, knit or sulfate fibers, comprising the' steps of mixing the same with a sodium hydroxide solution of mercerizing concentration at a temperature of approximately F in thefapproximate proportions of two 7 pounds of dry pulp to one to two-pounds of sodium hydroxide, while causing the temperature oithe same to drop gradually, washing the i'lber substantially free from'soluble reagents and lay-products, and diluting the pulp and running the same into the form of a paper sheet.

i JAMES L. McCLELLAN.

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