US1962882A - Process for finishing and conditioning paper - Google Patents

Description

June 12, 1934.

J. S. G. SHOTWELL PROCESS FOR FINIsHINc- AND CONDITIONING PAPER Filed May 29. 1950 2 Sheets-Sheet 1 bussa me/11410@ Jo//N llarmsu.

June 12, 1934. J. s. G. SH01-WELL 1,952,882'

PROCESS FOR FINISHING AND CONDITIONING PAPER Filed May 29. 1930 2 Sheets-Sheet 2 smear opfer.

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` "pplicaticn 'I'h'e inve"ntionA relates .to the manufacture of paper'and has for its objects to provide new land improved steps in finishing andl conditioning the paper before and durin'guthe calenderingpperation. l .i In nishin'g machinefmade papery it is necessary and desirablvthat lthe sheet be uniformly dry, thatfitslfiall ypossess a` moisturacontent of approximately,9,v to,10`%`, and thatA the surface be uniformlyfsiooth. 4` j l It is theobe'ct of .ther present invention. to `,ob-

tain thesedesirablefdiialities of thenished sheet by meanspfji'ilpaing; Vle'glllatiligand controlling atmospheric Vlnin1`idi-ty. adjacent ,the :sheet `or web from the timei'itfp'asses over the sweat ldrier up to and' includi paSSge through the calender rolls.v"j.By'; controlling the .atmospheric humidity atthese p" K tsfythe'paper. shaft or yweb is maintained inmune ',r'per meist conditin to e absorption of all 'portions of the sheetl f th. Y and uniform finish imparted by calendering rolls.

With such objects' iny view, as. .wellas otherad- Vantages which may be in cidentto theuse ,of the improvementsfthe invention'consists inthe vprocedure, and in the of thepartsi and combinations thereof hereinafter's'etforth and claimed, with the understanding that theseveral'necessary elements andsteps constituting the same may be varied in 4proportions andarrangement without departing from the nature and scope of the invention. y 1

In order to -make the invention more clearly understood there are shown in the accompanying drawings means for carrying the same intov practical `effect, without limiting the improvements, in their useful applications, to the particular constructions which, for the purpose o f explanation, have been made the subject of illustration. In the said drawings:-

Fig. 1 is a View in side elevation and somewhat diagrammatic in character illustrating the application of the invention in a preferred embodiment.

Figs. 2, 3 and 4 are charts illustrative of moisf2.9; 1930sem1,No.45v,46 In canada .nine 5, 192e 5S 1 clams' (creams) consequent. more perfect calendered, the fibers are soft and pliable and `are ironed out smooth and fiat and are properly ture variations in the sheet as determined by PATE Nt oli-rice I a I, PAPER 4 John s. c; Aslwtweu.@muntom;- N. J: if

, centerwet-'andionl calendering black streaks will :resulta '.(Fig: .2wshows'i diagrammatically the moisture content atl .various places across the -sheet.)-:` v

Invthe past itu-has been the practice to first overdry thepaperiand then; pass' this dry sheet over a sweat ,drierf a-:moistened cylinder, with possibly ka. .dampenedfelt coveredfroll `riding on the paper. This methodstillleaves unevenfmoisture conditions yand also possesses lthe'disadvantage of having a considerable portionxofthe water so added `lostwthrough` :evaporation-"before the paper is rolled-up;.alsofthislmethoddoes not help out the vunevendistribution A'(see Fig. 2) as an equal amount of moisture isadded across the sheet,

-ratherit increases lthe"blac1:ening effect. What is'desired is some tmetliodithat will tendto even Loutthe*moistureicontent of the sheet and such a methodfis described inthis application, and such a method is further illustrated by diagram shown in'Fig 4.'. i

,'Ifufthe paper. is :tool dryon reaching the calender `staclrsqthe'fibers w'ill be dry, stiff and brittle and instead fof-being ironed fiat andV smooth and Aproperly feltedewillremain stiff and give a fuzzy sheet,.those that are bent over will have a tend- `ency pto" break :and so weaken the sheet.

This secondfactalso increasesthe tendency to snap off inithexsstacks. yliiho-vvever, a damp sheet is feltedf together. sheet.

This gives a smooth stronger Kress and McNaughton studied the effect of atmospheric humidity on the amount of moisture that paper could hold. `'I'heir results were extendedand therate that paper will change its moisturecontent'under varying atmospheric conditionsnwasstudied by the applicant.

. .The results of these investigations are shown onchartsilllucstrated in Figs. 3 and 4. As much as"1.5% second may be gained or lost by the paper during calendering. In most mills the time taken for calendering is from three to six seconds so that considering the shortest time a possible gain of 4.5% or a loss of three (3%) per' cent may occur during this treatment.

Referring to these charts and also to Fig. 2, it seems that there will be a'tendency for the moisture to enter the -sheet more rapidly at the edges than at the center. This tendency will reduce the variations and give a more uniform moisture distribution across the sheet.

In the process claimed herein the principles, as

exemplified by the facts as shown on charts 2,

3 and 4, are utilized to produce and control the moisture content of the paper. By so doing a more even moisture content is obtained since the dry portion absorbs the atmospheric moisture more rapidly than do wet spots; by this means a higher average moisture content can be obtained which in turn will give a better finish to the paper and reduce "broke losses.

The humidity ,of the air around the calender stacks, reel and Winder may be controlled in several ways but the most satisfactory method is'to (1) Admit cool air of about 75 Fahr. and 95-99% relative humidity in the air jets on the calenders.

(2) Admit similar air under the calendersand just by the sweat drier.

(3) Admit air of about the same temperature and about 60% R. H. under the Winder.

This method would give the advantages of a good moisture in the sheet and added ventilation in the room. However, in place of cool air, hot humid air from the hoods might be used either being conveyed by means of ducts and admitted at the base of the calender and sweat drier and under the Winder or by the simple, but not so effective, means of slowing down the hood fans at the dry end of the machine and so forcing hot humid air to leak from under the hood into the space between the stacks and the driers vand from there into the room. These last two methods while cheaper than the first haveA the disadvantage of rendering working conditions unpleasant and unhealthy. Unpleasant and unhealthy working conditions have, of course, a direct effect on productions. .l

When using this process the paper is kept uniformly moist while passing through the calender stacks and a higher finish is obtained due to the bers being more pliable and also to the possibility of partially hydrating them.

The controlling factor may be termed either relative humidity, per cent humidity or absolute humidity, since it is the relative humidity at the surface of the sheet of paper that really matters and if the sheet of paper is at a higher temperature than the surrounding air, any given amount of water present in a given quantity of air will give a definite relative humidity at the sheet. It has been found in practice that the best results are obtained with a humidity of 7.5 to 8 grains of water per cubic foot of air around the calender and about 4 grains per cubic foot at the winders.

Referring to Fig. 1, the drier rolls or cylinders are indicated at 1 and the sweat drier at 2. The moist paper web 3 is conducted to the drier rolls, is thoroughly dried and heated and is conducted therefrom to the sweat drier 2 on the surface 4of a duct having a discharge outlet 9. In this ration of this uniformly applied moisture to the web, the latter enters thecalender stack 6 between the upperpair of a series of aligned calender rolls 7. Hot air of high humidity is con- .ducted by means` of suitably arranged exhaust ,fans from the air conditioners into the closed calender stack from below, for example by means case the film of water surrounding the exterior fibers, under the extremely high pressures of the calender rolls, will accomplish partial hydration of the cellulose and in extreme cases will have the effect of supplementary beating to the extent of forming a surface on the paper generally known as glassine.

This humidified air thoroughly and uniformly impregnates the paper web as the same is passed through the calender rolls thereby imparting to the paper the desired uniform smooth finish to a high degree. In cases where such a high' degree of finish is not desired, that is lesser or no hydration, the inner fibres or cellulose xnicells are maintained uniformly moist by 105 the penetration of the water vapor contained in the controlled atmospheres of the process. From the lower calender rolls the finished paper web is carried to the usual roll 10.

K The Winder is indicated diagrammatically at 11 where the finished sheet is wound on the rolls in the desired quantity. Highly humidified air from the duct 8 is admitted through discharge outlet 12 beneath the winder to insure against drying out of the paper during the winding operation. A further discharge outlet 13 in duct 8 releases cold humid air exteriorly of the calender stack as indicated by the arrows.

If desired supplementary nozzles 14 may be provided in the calender stack vfor blowing cold humid air on the calender rolls and the paper web passing therethrough.

What I claim is:

A process for conditioning paper without the use of steam, high temperatures and water spray, which comprises conditioning air to a predetermined water content and predetermined temperature, then conducting the conditioned air by conduits and emitting the air around a travelling web of overdried paper prior to calendering, during calendering and after calendering, whereby the' web is uniformly moistened to a predetermined degree.

JOHN s. G. SHOTWELL. 1ray

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