Patented Aug. 13, 1940 2,211,348

UNITED STATES PATENT OFFICE 2,21,348 METHOD OF MAKERNG GASSINE PAPER Robert F. Nelson, Ardmore, Pa., assignor to The Glassine Paper Company, West Conshohocken, Pa., a, corporation of FDelaware No Drawing. Application June 1, 1936, Seria No. 84,706 5 Caixias. This invention relates to an improved glassine ing run through the supercalender stack oper and method of making the same, and has particu ating in the usual fashion, . . . lar reference to a glassine of more uniform qual For the accomplishment of this last step, sev ity than that heretofore produced and a method eral variations may be introduced into the proc eSS. Under ideal conditions such as are presented. s whereby it may be produced with considerably With a narrow paper machine (from which the less waste of time than the present method in entire web may be run to a conventional super volves. calender without being slit), the greaseproof Glassine paper has heretofore been produced paper containing the proper amount of moisture by first forming a sulphite spruce pulp paper to produce glassine may run directly from the O commonly icnown as “greaseproof' paper, this dryers of the paper machine through the super Qaper being produced in a substantially dry state callender stack. It is only necessary in such case and containing only about 2% to 10% of moisture that the paper machine and supercalender stack removable by heating it to 212° F. This paper should be operating at corresponding speeds. is then moistened, for example, with a spray of 5 Water to add an amount which will raise the Paper machines such as are used in producing inoisture content to around 20 to 30%. The glassine can be satisfactorily run through a large inoistening is usually accomplished by unwinding range of Speeds, for example, fifty to four hun a roll of the greaseproof paper, subjecting it to dred feet per minute. The supercalenders can a spray of Water and then rewinding it. The likewise be run quite satisfactorily through a con siderable range of speeds from about thirty-five 20 water SC added is not initially uniformly distribu feet to five hundred feet per minute. It will be 2.3d 3ut remains on the paper in the form of obvious, therefore, that there is no difficulty in (ii'oplets. Accordingly the paper is permitted to Synchronizing the paper machine with a super Stand for a period ranging generally from about calender stack either by providing a common me three hours to three days, in order that the chanical drive or by operating the two machines 25 water Sprayed upon it will uniformly spread through the medium of synchronous or induction throughout the roll producing a greaseproof paper notors which have substantially constant spee containing the desired percentage of Water. Fol characteristics. lowing Sl?ch Spread of the moisture, it is Super The supercalender stack may be operated un calendered in the well known fashion by passing der conventional conditions which, as is well 30 3th it through a stack of heated Supercalendering known, may vary quite widely. The steam rollers rolls. The supercalender stack usually comprises used in Supercalendering are generally heated to both hollow steel rolls arranged to receive steam, a point in the neighborhood of about 300° F. and paper rolls. - though a lower temperature may be used or, if de in accordance with the present invention, the sired, this temperature may be exceeded. In gen 35 5 necessity for the interruption of the procedure involved in permitting the sprayed roll of paper eral, what is considered primarily is the effect to ecome uniformly moist is entirely avoided. of the high temperature upon the life of the paper in the preferable form of the invention, the rolls in the supercalender stack, the temperature paper machine is operated in the usual fashion being generally maintained as high as possible consistent with a long life for these rolls. 40 40 to produce a greaseproof paper from suitable con The feeding of a supercalender stack directly ventional stock. However, the drying is not car from the paper machine, even when the super ried out to the extent of obtaining a dry grease calender Stack may take care of a web of the full proof paper. In general, the paper, after paSS width of the paper machine, is generally attended ing the suction boxes and suction roll without with some difficulties which make it desirable to a pressure roll, and finally a suction roll with provide for accidental stoppage of the continu which is associated a pressure roll, Will contain ity of the paper. In general, the operation of a from 50 to 70% of water. 50% of moisture is approximately the upper limit which may be in paper machine is considerably more reliable than cluded when supercalendering is to take place. that of a supercalender stack, which may fail, for various reasons, to give satisfactory results. In 50 Preferably, after leaving the Suction roll associ the majority of cases, however, the failure of the ated with the pressure roll, the paper is passed supercalender Stack is minor and can be corrected through at least Some of the usual paper ma very easily, for example, when the failure is due chine dryers, preferably such as to reduce its to a sticking of paper to one of the rolls. A diffi moisture content to about 20 to 25%. culty of this sort may be corrected by stopping 55 55 The paper is then directly supercalendered, be 2 2,211,348 the operation of the stack for a very short time, is of the proper amount for supercalendering, releasing the pressure, cleaning it out, and then namely, between, say, 20 to 30%. The attain restarting the operation, all of which may take ment of uniformity of moisture content across Only a very short time. Because of minor the entire width of the web may be effected failures of this nature, it is desirable to provide, through the use of a blast of hot air directed between the paper machine and the supercalen against the central portions of the web as it der stack, a means such as a festooning arrange passes over the drying rollers of the paper ma ment, which can take up the amount of paper chine. The same result may be accomplished by delivered by the machine in a period of, say, five partitioning the Suction boxes and suction rolls 0. to ten minutes, so that the operation of the paper So that when leakage is taken into account a O machine need not be interrupted, The festoon greater Suction is produced in the central por ing arrangement may be of conventional type, tion of the boxes or rolls, thereby providing a normally being out of action but becoming effec lower moisture content thereat than at the edges. tive to provide a reservoir for the paper from the Thereafter, in passing through the drying rolls, 5 machine for a period such as that indicated dur the normal removal of a greater amount of 5 ing which the operation of the Supercalender moisture from the edges will result in the at stack may be corrected. Following such a cor tainment of substantial uniformity throughout rection, the supercalender stack may be operated the entire width, at a Somewhat higher speed than the machine 20 While a skilled paper machine attendant can, to take up the accumulated paper. by feel, quite accurately determine the moisture 20 Provision is also desirably made, however, to content of a web of paper, it is desirable, in the take care of more serious failures of the super present process, to provide automatic control of calendering stack by the provision of a reel on the end of the paper machine to reel up the paper the moisture content by the use of known devices 25 which regulate the entrance of steam into the having the desired moisture content, which paper dryer rolls and thereby maintain substantially 25 can be thereafter run directly through the same or an auxiliary supercalender stack. If desired, Constant the desired percentage of moisture in in fact, the web need not run directly from the the product. Control should, in general, be such paper machine to the Supercalender stack in any as to maintain the moisture content just prior to 30 the Supercalender stack at about 20 to 30%, 22% event, but the paper may be wound up on a reel being about the optimum moisture content. It 30 and the reel then moved to the Supercalender will be understood, however, that the moisture Stack So as to provide, in effect, a process hav content may vary considerably from this amount. ing a short discontinuity. The delay, however, About 15% is the minimum moisture content 35 need never approximate that necessary in the which is consistent with high transparency, present method and, furthermore, all spraying though even a less amount of moisture, say 10%, 35 Operations are avoided. may be used where surface finish is more to be de If the Supercalender stacks which are used are sired than transparency. The maximum amount narrower than the paper machine and it is de of water which may be used is such as to insure sired to run the paper machine at full capacity, that the Sup?rcalendered glassine is substantially the sheet may be split and wound on separate dry when it leaves the supercalender stack and, 40 reels prior to Supercalendering, though after of course, also such that there will be provided Splitting, the Separated webs may be run directly a sheet which can stand the supercalendering to individual supercalenders. operation without breaking or sticking to the Quite frequently another matter must be taken supercalender rolls. The maximum amount of 45 into account, namely, the fact that the paper moisture dictated by these considerations is about 45 coming from the paper machine generally has 50%. edge portions which are irregular and usually A plasticizer may be incorporated in the grease thicker than the center portions of the web. The proof paper in its passage through the paper ma thickness may be such as to prevent proper super chine. The plasticizer, which may be of any well 50 calendering. Accordingly, between the paper 50 machine and the supercalenders there are pref known composition, for example, that given in erably provided rotary knives bearing against a Bidwell Patents 1914,798 and 1,914,799, of course hardened steel roller for the purpose of removing adds considerable moisture to the paper. The ad such portions of the edge as might interfere dition after the paper is partially dry, has the 55 . advantageous effect of promoting uniformity of with the Supercalendering Operation. the moisture content throughout the width of 55 The introduction of the end of the web into the Web. Drying after the addition of the plas the supercalender may be very quickly accom ticizer should be carried out to such extent as to plished in the conventional fashion involving lo reduce the moisture content to the amount indi cating in the Supercalender a web of paper cated above which is desirable for Supercalender 60 while the pressure is removed from the Supercal 60 ender rolls, attaching, by the use of adhesive, the ing to produce a highly transparent glassine. end of the paper web to the trailing end of the A further variant of the process involves the paper strip in the Supercalender, pulling rapidly printing of the glassine before supercalendering. through the Supercalender the leading end of the In this variation the moisture content may, if 65 web, using the strip as a feeder, and then apply the ink requires a low moisture content to print 65 ing the pressure to the rolls and carrying on the properly, be reduced in the machine dryers Some supercalendering at the proper speed. what below the amount which would be Satis Usually in producing greaseproof paper little factory for immediate Supercalendering for the attention need be paid to the fact that the cen formation of glassine, say, between 10 to 15%, 70 tral portion of the paper web dries more slowly though preferably the moisture content is left 70 than the edge portions, since the entire web is as high as possible. This amount of moisture run to the condition of substantial dryness. will not generally prevent printing of the paper However, in the present instance the Web should by the use of inks such as those of “vapor' type, have a substantially uniform moisture content which are adapted to be dried by the application 75 throughout its width, when the moisture content of heat. A press driven in timed relationship 75

2,211,848 3 with the paper machine may accordingly be out the sheet cannot be attained by a second located directly at the dryers which reduce the moistening of a dried sheet. A high degree of moisture content to the desired degree. There transparency can only be approached when the after the paper may be passed through the con moisture content is uniform throughout even ventional ink drying apparatus, such as one de quite small areas of the Web. signed to raise its temperature to an extent that What I claim and desire to protect by Let ters Patent is: will evaporate the superficial ink solvent and 1. The method of making glassine paper in cause the ink to dry without, however, reducing cluding sheeting a thoroughly hydrated chemical to a very substantial degree the moisture content. stock from a coniferous tree Suitable for the O O The ink so dried becomes quite waterproof and, formation of a "greaseproof' paper, partially after such drying, if necessary, additional water drying the resulting sheet to a moisture content may be applied to the Web, preferably on the between 10% and 50% suitable for Supercalen side opposite that which is printed and then dering to produce glassine, and supercalendering again partial drying may be effected to now Said partially dried sheet without Substantial 5 5 bring the moisture content down to the percent change, prior to supercalendering, of its mois age which is most desirable for Supercalendering, ture content resulting from the partial drying. namely, about 20 to 30%. The paper may then 2. The method of making glassine paper in be Supercalendered. cluding sheeting a thoroughly hydrated chemical Instead of adding water alone following the 20 printing, the water may contain in solution the Stock from a coniferous tree suitable for the for 20 usual plasticizing substances such as Sugar, this mation of a "greaseproof' paper, maintaining Solvent for the plasticizer Serving additionally to the moisture content of said sheet from the time add an excess of water, the major portion of of its formation up to the time of supercalender which is removed in the subsequent drying oper ing in excess of ten per cent, and supercalender ation. When there is only in the paper the ing Said moist sheet to produce glassine, the mois 25 amount of moisture necessary for supercalender ture content of the sheet immediately prior to ing, the Supercalendering operation will not supercalendering being between 10% and 50% affect the printing ink, which may be of the so and being secured directly by a reduction of called "vapor' heat drying type. However, any moisture content. ink with a sufficiently volatile solvent to produce 3. The method of making glassine paper in 30 30 rapid drying upon heating may be used. It may cluding sheeting a thoroughly hydrated chemi be noted, in this connection, that greaseproof cal stock from a coniferous tree suitable for the paper containing 20% of moisture is only very formation of a "greaseproof" paper, maintaining slightly damp to the touch. the moisture content of said sheet from the time Sometimes, as in the case of the manufacture of its formation up to the time of supercalender 85 of candy box linings or cups for the reception of ing in excess of ten per cent., trimming off the candies, it is desirable to add a wax emulsion edges of said sheet, and supercalendering, the before supercalendering in order to substantially moist, trimmed sheet to produce glassine, the increase the slip of the paper surface. It will moisture content of the sheet immediately prior be clear that such emulsion may be added to the to supercalendering being between 10% and 50% 40 paper in the form of a fine spray just before the and being secured directly by a reduction of supercalendering takes place. - moisture content. From the above it will be clear that there is 4. The method of making glassine paper in avoided the unreeling, spraying and re-reeling cluding sheeting a thoroughly hydrated chemical Operation heretofore involved in the manufac stock from a coniferous tree suitable for the 45 ture of glassine, and even more important than formation of a "greaseproof' paper, maintaining the avoidance of this operation, the delay which the moisture content of said sheet from the time is necessary to secure a unifornity of the mois of its formation up to the time of Supercalender ture throughout the Web by slow spread from ing in excess often per cent., printing upon said droplets. As the Web is partially dried in the paper while its moisture content is in excess of 50 50 paper machine, the moisture is quite uniform ten per cent, drying the ink on said paper by Over extended areas, the only lack of uniformity the application of heat, and supercalendering being due to a greater excess of moisture in the said moist printed sheet to produce glassine, the central regions of the paper. There is nothing, moisture content of the sheet immediately prior however, in the nature of droplets on the sheet. to supercalendering being between 10% and 50% 55 55 In accordance with the present invention, the and being secured directly by a reduction of paper is Supercalendered when the moisture con moisture content. tent is brought down to the proper amount, suit 5. The method of making glassine paper in able precautions being maintained to insure that cluding sheeting a thoroughly hydrated chemical the uniformity is not only local but also existent stock from a coniferous tree suitable for the for 80 60 throughout the entire width of the Web. mation of a "greaseproof' paper, maintaining An improved product results from the super the moisture content of Said sheet from the time calendering of a greaseproof sheet which has of its formation up to the time of supercalender never become dry. The removal of moisture from ing in excess of ten per cent, printing upon said a moistened, previously dried Web is quite detri paper while its moisture content is in excess of 65 65 mental to its strength and also to the trans ten per cent, drying the ink on said paper, and parency of the product which results from super Supercalendering said moist printed sheet to calendering, possibly due to the Setting of the produce glassine, the moisture content of the fibres upon the initial drying followed by some sheet immediately prior to supercalendering disturbance therein on subsequent moistening being between 10% and 50% and being secured O 70 and the second drying. In any event, the ideal, directly by a reduction of moisture content. perfectly uniform content of moisture through ROBERT F, NESON,