US2617743A - Method of making coated paper moisture resistant - Google Patents

Description

R. J. GRIMM Nov. ll,- 1952 MFII'RX) OFIMAKING COATED PAPER MOISTURE RESISTANT- Filed llarGh 8, 1952 Am. Bussum:

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Patented Nov. 11, 1952 METHOD OF MAKING COATED PAPER MOISTURE RESISTANT Richard J. Grimm, Whitesboro, N. Y., assignor to St. Regis Paper Company, New York, N. Y., a corporation of New York Application March 8, 1952, SerialNo. 275,605 I 3 Claims. (Cl. 117-64) f This `invention relates to methods for manu-- facturing moisture resistant paper, the invention beingparticularly adapted, among other possibilities, for the production of relatively vinexpensivel coated paperV adapted for high speed lithographic printing. `In lithographie printing the plate rolls used are ordinarily kept in clean condition by aqueous mixtures, with the consequence that small amounts of moisture, along with the ink, are carried onto thepaper duringprinting.y .With this method of printing, particularly if coated paper is used and is 'travelling at a high speed (for example800900 feet per minute) such moisture is suicient to cause particles of the coating to be released anddisplaced or picked off, thus seriously interfering with good quality printing, unless the paper coating is in somewaymade moisture-resistant. f L

To. providev such moisture-resistance, it has heretofore been common practice to coatr the paper off the machine, that is, as a separate operation after .the paper leaves the papermaking machine. In such cases casein-claycoating mixtures have been commonly used incorporating an ingredient such as formaldehyde which has the property of rendering water lresistant such ,adhesives asl casein. Since with such off-the-machine coating,

. thespeedlof the paper during 'the coating operationiis lrelatively slow, the coating composition usedpmay comprise a quite thin mixture'thatis, a mixture of'lovv viscosity and having a high water content, and hence sufficient amounts offormaldehyde solution may be incorporated 'therein with-V out causing the coating mixture to harden before itis properly applied or distributed on the paper as acoating.y Howeventhis method of producing a moisture-resistant paper for the purpose -has the disadvantage that the coatingA of `the paper relatively slowly as an operation separate from the manufacture'of paper, involves a substantial extra. expense` as compared with the cost of modern high-speed methods of coating paper on thepaper making machine. Accordingly elforts haveheretofore been made to provide some way by which paper could be coated on the paper making machine, or Without an extra handling operation, to provide a product sufciently moisture-resistant for high-speed lithographie printing purposes,` and with avoidance of the extra cost of off-the-machine coating which may amount to 50% or more. To this end attempts have beenmade to incorporate in the coating mixture on the paper making machinevmaterials such as formaldehyde or other ingredients for Cil 2' rendering the coating moisture-prooff However, since coating paper at the necessary lhigh speeds :on the machine requires the useof a mixture having a high solids content so that it will quickly dry, it has been found that attempts to introduce formaldehyde into such a mixture caused the .coating material to more or less solidify so rapidly that it could not be properly applied and uniformly distributed on the paper as a coating. Attempts'to use other chemicals for the purpose during coating on the paper machine have not, so'ffaras is known, met with any substantial commercial success, for various reasons. z y

yOther attempts tosolve the problem have in volvedcoating the paper on the machine and lthen the application ofa Waterproong agent such as formaldehyde'in aqueous solution to the coated paper as it passes over the calender at thefend of the paper machine. Still other attempts have'involved the application of formaldehyde as agas to the paper after. coating. These attempts also', so farr as is known, have not met with anysubstantial commercial success and involve difficulties of securing uniform treatment throughout the surface of the paper, and also vthe very serious difficulty that formaldehyde, as an obnoxious gas, escapes into the room to such a serious extent that it cannot be tolerated by theworkmen.

According tothe present invention, paper vis coated by known methods preferably at high speed on the paper making machine by applying thereto known or conventional"`coating mixtures embodying a pigment such as clay anda proteinaceo'us adhesive such as casein (or a proteinaceous adhesive Vsuch as isolated soya protein as commonly used in paper coating mixtures), and then as the paper leaves the dryer rolls of thev paper making machine and is about to pass through the machine calender stack, or later as itk isabout to be passed through the usual supercalenderfit is treated with formaldehyde by incorporating the formaldehyde in the so-called steam showers,-

such as are customarily used for applying steam to the paper on supercalenders. the preferred method, an aqueous solution containing for example from ILO-40% of formaldehyde) is allowed to drip vinto the hot interiorn'of the steam shower enclosure so that formaldehyde gas is entrained in the streams of steam whichv are projected throughsmall exhaust apertures onto the paper just as the paper is to pass between the rolls of the calender.

serve forcefully to apply `the formaldehyde, caus- According Vto Thus the customary steam showers which are used to softenl the paper and the coating vthereon at the calender,`

ing it effectively to penetrate the web surface and impart the desired moisture-proof characteristics to the adhesive thereof, and since the application of the formaldehyde in this way is immediately followed by the compressing and smoothing of' the paper between the calender rolls, the method has the effect inf-insuring thoroughpenetrati'onof L the adhesive by the formaldehyde and the'prn'pt locking, in eiect, of the formaldehyde into the surface of the web. At the same time it has been found that this method of projectingthe formal-wdehyde as embodied in expanding jets of steamY-f onto the paper is surprisingly effective in preventing objectionable escape of the obnoxious gas'into"-"-f the atmosphere of the room. Other and more specic objects, features and advantages of the invention will vappear Hfrorn'the if detailed description given below, taken in con-.- nection with the accompanying drawings which"A form a part of this specification and illustrate by wayef 'example' one formA ofV equipment whichmay' be usedin carryingout 'the invention('Th'einventionconsist's in such novelu features and I'come binatioiffs'of features as may be hereinafter more specifically pointed'out and specified `in the'ape' pen'dedcl'aimsf. l

In the? drawings :i

Fig." '15 is a side view; somewhatdiagrammatic,' l of a" siip'ercale'nder equipped 'and'arrange'd with steainshowers 'and associated special equipment"` for"'carryin`gout the inventionin the preferred way;""""

Fig. 2 is an enlarged transverse sectional 'vievvff through 'one'of the' Msteam showers'showing 'the preferred'means by Vwhich'the formaldehyde Amay Fig' isalOngitddinal sectional'viewoi por'-V reference" character' S, 'and "others "having fiber' surfacesl of conventional type'as indicated by the referencecharacter F. "So-called y rvolls-'are indicated at 20,' 2|` etc. for guiding thevpaper'as' J it emerges 'from' between the nip of adjacent rolls,

into the -neir'tnip of the rolls.'r The paper' maybe? fed as from a roll"22 onto the' top roll ofthe calender' and thence' down' Ythroughy 'the' calender ontof'a powerldriven' wind-up roll 23 of conven-` tionaf'drm.

35 running to waste, whereas the remaining steam passes up around between the walls of cylinders 32 and 34 to either a slot or a series of apertures B positioned along the top of the cylinder 34, and along a line transverse to the moving web closely adjacent thereto, sothat a jet or jets of steam' :3T frcefu-llyiimpingelponithe Ylpipferfweb. In r'dei" t`o"'embdy the`f'frmaldelyde"in the steam jet or jets 31, preferably a tank as at 4D is provided, connected by piping as at 4I to a pipe 42 extending-longitudinally of the space between thefcylinders'f' and 32. The lower side of pipe 42 is provided either with spaced apertures or a series 4'of sprayers-'as 'at-42' (Fig. 3) permitting liquid'tobe'sprayed o'l'it at a rate subject to regulationas 'lierei'naft'erdescribed onto the exterior of the'pipe or `cj'fli'nder 3U'- which is being maintained in heated condition by the presence of the steain"An aqueous 1040% solution of the formaldehyde may be used in thetank 40. However. the' percenta'g'-'f the 'solutirmaybe 'fvaie'd-f Withinf'wide-limits'-- 'i' l y n Y At least'i the' fm'ajor part-lof th r-r''a'ld'ely'd solutionisprayeid'onto tlie'fheated'fit' ioifo Y 'th pip'efo'r cylinderf-a' is vapri'z'e'df'fandthorelglily- 'mixed with and carried along by the steam1 throu'g-lthe orifice' or'apertii'e 736,'

St'en" 'showers`"are indicated at '2li 'and 25 for applying steam"V to the' opposite surfaces ie' spectiviyo'f the paper. It wiube noted'thar each' t0 thturfac 0f the paper which is about t0 b engagedlrsuccessively by a plurality of 's'teel'rolle'rs' which'act toiron out and polish the paper surface'.

That is, theV steam'shower 24 ispositionedto apply steam to that 'surface of the paper. which is to be engaged by the steel rollers l0 and I2, andthe As indicated in Fig. 2, the'fo'rm of steain'show'er" means `here used'may-comprise central steam'inlet pipess, '39 extending transversely of the moving I' webaiid'having a slot or' a series' of apertures at 3i forpermitting the steam to escape" into an 32 aidfihto an outer' cylinder'34. 'Condensatie g drains'from the latter cylinder through 'aconduit otherwise.

snrfac'e"eitherl by reason of dissolving'the 'g' sjin the iine'particles' 'of vresulting condensatef'ior The draining of condensate 'fronithe'bbaomr Y cf the.' vste'arnshowers throughpipe'slas at 35 'jv will insure that the steam it passes @through f then'ricesat 36 will be substantiallyv dry'ahdfreeof droplets ci water whichwouldim'part a` non-uniform treatment tothe web. 'At the' sa'm time any excess@formaldehyde solution 'which is' not substantially vaporized'and jentraiii'ed'rin the" escaping stearnrwi11r te drained 'away through'- both thesteam and formaldehydetreatments onl the web will be uniform. f A i It lwillloe apparent that theiinvention may be applied to the treatment of paper board as well as-paper and other Webs, coated or uncoated, and which embody adhesives capable of being'ren'-4 dered moisture resistant by the action of formaldehyde.' Y

ment lfor carrying out this method is small, since equipment essentially comprises the available calenders or supercalenders and accompanying steam showers. While it is believed not to be essential that any special Ventilating equipment `l() It will be apparentthat the expense for equip- Y or hoods be provided for confining or carrying aWay escaping vapor, if desired the upper surface of each steam shower may be provided with baille plates or walls as at 45, 46 interconnected at their ends by properly shaped end pieces so as to provideg'a chamber 41, the top of which is substantially closed by the moving web. This structure willi tend to conne the steam and vapor for somewhat more effective treatment of the paper.v

QWhiIe the method is preferably carried out during the supercalendering operation where,`

steam shower facilities are usually already availm able, it will be apparent that similar steam' showers might be applied to the usual calender at the end of the paper making machine (which,` t of course, follows the usual dryer rolls of th e riiachine) to permit the use of the invention atv that point if preferred, or in cases where superi calendering of the web may be unnecessary.

r The temperature and amount of the steam used Highly satisfac-j does not appear to be critical. tory results have been obtained using steamv showers the same as customarily used in supercalendering coated paper. For example the steam entering the cylinder may be at a tem-.

perature in the neighborhood of 255 F. and at a pressure of 60 lbs. The amount of formaldehyde in solution used is also not critical, although it is desirable that enough be used so that continuous sprays thereof will be directed onto the cyl-'- inder or pipe 30. As above indicated, the percientage of formaldehyde used in the solution may also be varied within wide limits as only a small quantity is necessary in treating the coated paper for the above-indicated purposes, and any excess will be drained away inthe condensate passing out through pipes 35. The coated paper treated in accordance with this invention has been found to present a highly satisfactory surface with improved gloss for high speed lithographie printing, particularly for multi-colored printing. One suitable form of regulating apparatus for supplying the formaldehyde solution will now be described in connection with the enlarged Viewv thereof shown in Fig. 2 and a View thereof on a smaller scale in Fig 1. The commercially avail-7' able formaldehyde solution may be supplied as in a barrel 54, which is subjected to air pressure as by compressed air connection 5|, the solution passing from the barrel through a shut-off valve ,'52 and a pipe 53, preferably having a check valve ,as at 54 at a point prior to its entry into the tank 48. Within or adjacent the tank 40 a ing valve 55 of suitable known type may be provided for mixing the solution with a desired pro,-v portion of water coming in through a water supply line 56 and a check valve 51. The mixing valve may also be of a suitable oat controlled` type controlled in a known way as by a float 58S`- in the tank40 and arranged so that whenever formaldehyde solution, but whenthe tank 4U is filled toa predetermined level, the Vmixing valve will shut off the supplies of both the water and: solution. VThe tank 40 is also preferably con# nected to an air pressure line as at 60 entering' through a pressure regulating valveV 6I having a vent pipe `62 which will'be opened by the pressure regulating valve whenever the pressure in the tank 48 is greater than the pressure', as supplied by pipe 60 regulated by valve 6l. The barrel 50, for example, may be subject to a pressure of 30v lbs. per square inch, Whereas the tank 40 may normally be subjected to a pressure, for example, of 20 lbs. per square inch. 'I'hus when the mix-i ing valve 55 is opened by the iioat, the tank 40 will be subjected to pressure from the barrel higli enough to allow the mixed liquids to enter, and suicient air or vapor above the liquid in the tank 48 will escape through the vent 62 to allow the liquid level to rise to the desired predetermined point as controlled by the float.

The piping 4| for carrying the solution into the steam showers preferably is provided With a soleheid-operated shut-oil` valve 65 and the steam pipe 36 may also be provided with a similar valve 55, both these solenoid valves preferably being operable by the same circuit as indicated in Fig. i and arranged so that when the electric current is shut off, the flow of both solution and steam to the showers will be cut off.

As indicated in Fig. 1, the solution and steam may be carried to the shower 24 by branch pipe i lines Illa and 36a respectively, which are connected to the piping 4l and the steam pipe 30.

While in the interests of economy in the u 'se of formaldehyde, some special means is desirable for mixing the commercially available formaldehyde solution with water and for regulating the supply of the mixture properly under pressure, means other than that shown may, of course, be used such as mixing tanks from which the solution ows by gravity into the steam showers.

This application is a continuation-in-part of application Serial No. 143,185, filed February 9, 1950, now abandoned.

While the invention has been described in detail with respect to particular preferred examples, it will be understood by those skilled in the art after understanding the invention, that various changes may be made and equivalents may be used without departing from` the spirit and scope of the invention,

What is claimed as new and desired to be secured by Letters Patent is:

l` In the calendering of a dried paper web which has been coated on the paper making machine with a mixture embodying clay and www whi'ehhais-beenfcoatedwith a; mixture embodying: clayind'fsoywproteinf adhesive, the .method of providingftheidred'web Witha'rnoisture-resistant glossyi'print ifeceptive fsurface suitable for `high 1 5 speedV l"lithog'lfampl'iic-' printing; which comprises facfhas been effectively` calendered:

clayfand an-fadhesiversel tedfjjrom ,thegroup j; oonsis'tingrof easeing andsoyafprotein. the method Y of lprovidirrfithe-#driedfwebl *with a .moisture-fw; resistant glossy print receptive-surfamefsuitable` for highfspeed iitho'graphic printingi'whichfcom-i prises forming-an,intimateintermixture'of 'steam andformaldehyde,iimpinging*said'mixture onto a.. f coated' fac'o'f theidied coated-'Web and imrnedi-' ately: subjeting'the thusi'treate'd'face of the web v' vto the ironing action of calender rolls until such facet has` been 'eiectively" c'alendered:

RICHARDfmGRn/LMA f

Claims (1)

1. 3. IN THE CALENDERING OF A DRIED PAPER WEB WHICH HAS BEEN COATED WITH A MIXTURE EMBODYING CLAY AND AN ADHESIVE SELECTED FROM THE GROUP CONSISTING OF CASEIN AND SOYA PROTEIN, THE METHOD OF PROVIDING THE DRIED WEB WITH A MOISTURERESISTANT GLOSSY PRINT RECEPTIVE SURFACE SUITABLE FOR HIGH SPEED LITHOGRAPHIC PRINTING, WHICH COMPRISES FORMING AN INTIMATE INTERMIXTURE OF STEAM AND FORMALDEHYDE, IMPINGING SAID MIXTURE ONTO A COATED FACE OF THE DRIED COATED WEB AND IMMEDIATELY SUBJECTING THE THUS TREATED FACE OF THE WEB TO THE IRONING ACTION OF CALENDER ROLLS UNTIL SUCH FACE HAS BEEN EFFECTIVELY CALENDERED.

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