US2597087A - Synthetic resin coated paper - Google Patents

Description

i atented May 20,

2,597,087 M r sYNrnE'r-roREsIN COATED-PAPER William Cowgill, Fairfield, Conn., assig'nor to United States Rubber Company, New "York,

N. Y., a corporation of New Jersey No Drawing. Application April 9, 1951, serial No. 220,127

, '1 This invention relates to coated paper and moreparticularly to paper having a glossceat- 'ing andusefulwherevera paper product having a highgloss finish which greatly improves its appearance and reduces moisture vapor transmission is useful, particularlyfor displaypurposes, as for the fabrication of containers, and wherever a'paper or paperboard having a'highly glossedfmishof reduced moisture vapor transmission is desired. I

Thisjapplication is a continuationin-part of :my prior-and copending application, Serial No. 54;,211, filed October 12, 1948, now abandoned.

Heretofore paper (which term is'used herein to include bothordinary paper of a high flexibility and paper board, such as cardboard or the like) hasbeen provided with a glossy finish by various methods. One of these methods involves layingasheet of preformed transparent foil oi thermoplastic material over thepaperand apply- .ing heat and pressure to cause the foil to adhere to-thepaper. The product made in this manner is subject to the objections of the great expense of manufactureand the marked tendency of the applied foilflayer to separatefrom 't'hep'aper lbase uponh'andlin'g and use. Anothermethod involves the application of a solutionbf a resinous therma iasucypoiymemn' a volatile organic solvent .to'thepaper base followed by removal 'ofthe solvent by drying. However, the product of this methodha s been unsatisfactory in that the resinous solution penetratesintothe paper to an obiectior' fable'extentwith the result that the flexibilit'yj'of the product is'impaired. Furthermore, the product has been undulyfexpensive. Other methods of providing paper with'glossy' resinous finishes has'been proposed, but so far as I am aware,none,of them has been suitable for use on alargecommercial scale. The result is that the industry has 'not heretofore had available a glossed paper product sufficiently cheap to, be used widely, for example in magazine production and container manufacture, and possessing the necessary combination of physical properties adapting it tosuch large-scale usage.

invention'resides in the discovery thata glossed paper product meeting the reduirements for'wide commercial utilization may be obtained byproviding on one or both surfaces of the paper a thin, continuous, flexible, transparent coating of polymeric material selected from the group consisting of a resinous'copolymer of styrene and acrylonitrile in proportions of from 65 to 80% by weight of styrene and correspondingly from 35 tb-'20% byweight ofacrylonitrileand mixtures ream. (01. 117 155) of from 50 to 95% by weight'of said resiriouseepolymer and correspondingly from 50 to 5% by weight of a rubbery copolymer of butadiene-l','3 and'acrylonitrile, the coating being manifested as a highly glo'ssed film tenacious'ly a'dher'e'nt'to the surface ofthepaper and thefamount ofthe coating ranging'frorn 0.1 to -3.0 pounds of said polymeric materialper 1000 square'fe'et'ofcoated surface. So far as ramaware; paper has never been successfully commerciallyglos'sed' withsuoh a small'amount of'polym'e'ric material. At the same time thecoated paper product of myii'iiivention is distinguished byits "excenent flexibility, absenceof taste, odor 'orfiavor, markedly'reduc'ed moisture vapor transmission, absence of any tendency of the glossy coating to separate 'rrom the paper base,'freedorn from any tendency to block (bywhich is meant solidification of a'plurality of superimposed coated sheets into a block at ordinary orfmoderately' elevated temperature) high resistance to oiland'grease, goodabrasionand scu'li-res istance, and goodiohrnicaliesish ance and resistance to sunshine. ,.Where the glossed coating of my invention 'isapplied" paper'which has been printed I or lithograp ed with colored inks,the glossycoating exerts a ver definite protective effect upon the. colored inks, protecting them from 'fa'ding uponexpos'ure to light.

:Theresin used. in theQprac'tioebf my intention is a copol'ymer rmonomerseonsisung essentially of styrene andacrylonitrile. rhave obtainedunusually successful re'sults iwith airesmousce oim mer of by weight 'oristyrene and,30 %[b'y weight of acrylonitrile. While, as previouu indicated, such a resinous copolymer of styrene and acrylonitrile can be the sole, polymeric material in the glossed Coating, eVh better. results are" ob- I named, particularly where, very highffle'xibility of the coating 'is desired',fas'ih coating paperboard ,to"give aipro'duct particularly suitable for manufacture, of 1 folded "containers where, the glossed paperboard product or Tiny invention 'is subject to being bent sharply'during fabrication ofthe' container with the're's'ult that the'co'at'in is stressed, by incorporating with such'aresinous copolymer of styrene and aorylonitrile a "rubbery copolymer of monomers,consisting-essentially of butadiene-'-1,3 and acrylonitrile. Thisfnot, only markedly increases the flexibility of theifcoatin'g but also imparts higher resistance to transmission of moisture'vapor. I The resinous styrene-acryionitrile copolyfin'er and the rubbery buta'diene acrylonitrile copo-lymer'are completely compatible with each-other so that in the glossed film they form a mutual solid solution in one another.

The resinous copolymer of styrene and acrylonitrile may be prepared by the aqueous emulsion polymerization of styrene and of acrylonitrile as disclosed in U. S. Patent No. 2,140,048, in the presence of an emulsifying agent and a polymerization catalyst. The customary regulators or modifiers used in making Buna N synthetic rubber may be included, such as those of the mercaptan or other type. Following polymerization the resulting latex is stripped in known manner to remove any unreacted monomers and is then ready for direct use in making the coated paper product of my invention.

The rubbery copolymer of butadiene and acrylonitrile is a well-known synthetic rubber of the type commonly designated as Buna N. Its manufacture is Well-Known, it also being made by aqueous emulsion polymerization. Following polymerization and stripping the resulting latex is suitable for use directly 1n admixture with the above-described styrene-acrylonitrile resin latex. The relative proportions of butadiene and acrylonitrile employed in the monomeric charge may vary within the known limits which give a rubbery elastic copolymer Generally the rubbery copolymer comprises between 50 and 75% of combined butadiene and correspondingly between 50 and 25% of combined acrylonitrile.

The relative proportions of the resinous copolymer of styrene and acrylonitrile and of the rubbery copolymer of butadiene-1,3 and acrylonitrile may vary widely depending upon the properties desired. However, I prefer to employ between 50 and 95% by weight of the resinous copolymer and correspondingly from 50 to 5% by weight of the rubbery ccpolymer, these percentages being based uponthe sum of the resinous copolymer and the rubbery copolymer. I usually prefer to effect the intermixtur of the rubbery copolymer with the resinous copolymer by simply blending a latex of the butadiene-acrylonitrile rubbery copolymerwith a latex of the resinous styrene-acrylonitrile copolymer in the indicated proportions after which the resulting mixture is applied to the paper, dried and calendered in the manner described in detail below.

The coated paper of my invention is prepared by applying to the paper an aqueous dispersion of the amorphous thermoplastic resinous or res-v inous and rubbery material in an amount such that the weight of solids, i. e., of polymeric resinous or resinous and rubbery material, applied ranges from 0.1 to 3.0 pounds per 1000 square feet of coated surface followed by drying to remove the water and set the polymeric material on the paper in the form of discrete particles adhered to the surface of the paper and constituting a discontinuous film, and hot calendering of the solids deposited from the aqueous dispersion to effect glossing by converting the solid discrete poly-. meric particles to a continuous film manifested predominantly as a surface film. One method of effecting the production of the product of my invention is described in my copending application Serial No. 769,046, filed August 16, 1947, now Pat. No. 2 554,662 issued May 29, 1951, in accordance with which the paper after being coated with the aqueous resin dispersion is dried at a temperature ranging from 20 C. to 60 C. above the second order transition temperature of the resinous polymer, after which the dried coated surface of the paper is pressed against a heated surface, typically by subjecting the coated paper to an even-speed calendaring operation in a calender having a highly polished (preferably mirror-finish chromium-plated) heated roll in contact with the coated surface of the paper, at a temperature ranging from 40 C. to C. above the second order transition temperature of the resinous polymer whereby the resin particles on the surface of the paper are converted to a thin, continuous, strongly adherent coating, whereupon the hot glossed product is stripped at the latter temperature from the heated surface.

When using a dispersion wherein the polymeric material consists of a 70% styrene-30% acrylonitrile copolymer resin having a second order transition temperature of approximately C., I have obtained very excellent results by dry ing the coated paper at a temperature of from to C. followed by glossing by contacting under pressure with a highly polished (mirror-finished chromium-plated) calender roll at a temperature ranging from 135 to 150 C. These temperatures have reference to the actual temperature to which the coated paper is heated. The drying is carried out while the coated paper is not in contact with any solid material, 1. e., while it is in a heated gaseous atmosphere. The temperature to which the mirror-finished chromium-plated calender roll used for glossing is heated will vary with the speed at which the glossing is conducted. For example, when employing relatively low glossing speeds, say, when passing the coated dried paper through the calender at lineal speeds of the order of 60 feet per minute, the glossing roll may be heated to a temperature of say 135 C. whereas when operating at higher lineal paper speeds, say of the order of 300 to 350 feet per minute, the glossing roll often must be heated to a temperature of the order of 150 to or even higher in order to bring the paper and its coating to within the temperature limits given.

When a dispersion of polymeric material consisting of a mixture of the styrene-acrylonitrile resin-ous copolymer described above and a butadiene-acrylonitrile rubbery copolymer as described above is used in the practice of my invention, the method of application to obtain the high gloss desired is preferably that shown in my copending application, Serial No. 133,183, filed December 15, 1949, now Pat. No. 2,554,663 issued May 29, 1951, in accordance with which the paper is coated with the aqueous dispersion, is then dried to remove the water and heated at a temperature of from 20 C. to 60 C. above the second order transition temperature (T2) of the resinous copolymer (while the coated surface is out of contact with any solid surface) to set the polymeric material on the surface, is then fed continuously into the nip of a continuously rotating, heated, hard non-resilient, mirror-finished (preferably chromium-plated) glossing roll and a cooperating continuously rotating resiliently surfaced roll rotating at a speed identical with the glossing roll, so that there is no relative movement whatever in the nip insofar as the coated paper and the two rolls are concerned, with the polymer-coated surface of the paper Web in contact with the glossing roll, passing the paper web around the glossing roll in intimate contact therewith and while stationary with respect thereto for a substantial angular distance, preferably at least C., heating the coating to a glossing temperature ranging from is at thetemperature to which it was heated by the .glossing roll, .i. .e... without cooling, and. continuously passing the stripped'web in .a straight line. while maintaining the hot coated surface out of contact with any solid surface, until the coatin; cools to such an extent that its gloss .is not injured by bending.

The glossing machine used to produce the product; of the present invention is preferably constructed in accordance with my copending application, SerialNo. 195,966, filedNovember 16, 1.950...

The above. described resinous copolymers of styrene and acrylonitrile and mixtures thereof with butadiene-acrylonitrile. rubbery copolymers impart tov the resulting highly glossed coating the properties of good abrasionand scuff-resistance, high resistance to the transmission. of moisture vapor, low or no. odor, taste or flavontransparency, good flexibility at the temperature encountered in. use, high resistance tooilandgrease, good adhesion to the paper,v low combustibility,. good chemical resistance. and resistance. to. deterioration uponexposure to sunshine. In addition, the coatings obtained are heat-scalable both to themselves and to. uncoated paper surfaces This allows heat-sealing of. the coated. product during fabrication of. containers or the like therefrom.

The proportion of dispersed resinous polymer or of resinous and rubbery polymers in the aqueousdispersion used to prepare the product of my inyentionwill. generally range from 25 to 45% by weight and preferably from 30 to 40% by weight.

The amount of the aqueous. dispersion. of the polymeric material applied to the paper in making. the product of my invention is such. that from 0.1; to 3.0; pounds. of resinous copolymer or. of.

resinousand rubbery-copolymers are applied per 1000,,square feetof coatedpaper surface. For many; applications. the amountimay range from. 0.5129 3; pounds per 1000. square; feet. However;

there. are many situations in which amounts ranging from 0.1 to 0.5 pounds per 1000 square feetareused with the: production of a highly glossed product. Forcontainer stock the amount of solids applied usually is in the upper portion of the broad range. often ranging from 1.5 to 3 pounds per 1000 square feet of surface.

In somecases the paper may; be givenia light absorptionis i not. completely prevented since. otherwiserthe,adhesion, of. the; glossed polymeric" film tothe paper hase may-heseriously-reduced.

6 In fact, :even whenv such rare-treatment or the paper'is omitted, the penetration of the solids content vof the aqueousxdi'spersion into'thep'a per generallydoes not exceed 20% by"weight oT-the said solids content, this being attributable to the filtering and/or precipitating-action of the paper upon the aqueous dispersion whereby the solids content thereof is laid downupon theapaper-asa separate and distinctfilm. Whenthe-aforementioned pre-treatmenttis used. the 'extent'o'f penetration of the aqueous-dispersion into the paper will generally. range from 1 to 20% by weight-of the solids and .in-imost cases will not exceedloiq'b thereof.

Following is 'anrexample of the preparation-of the product of :my inventionin accordance with the best practice now known to me.-

Example There is first prepared an aqueous dispersion of a resinous styrene-acrylonitrile copolym'er containing of combined styrene and 30% of combined acrylonitrile. This dispersion is prepared by polymerizing the following recipe:

Parts by weight- This recipe is polymerized at 50"" C. for 5 to 15 hours and is then stripped, yielding a white latex' having a solids (copolymer) content of 36% and a pH of 3.0 to 5.0. With this latex is admixed-0.6 part of Duponol ME and 0.6 part of- Daxad 11 per parts of solids content; The resulting latex is then blended with a latex of Buna N which contains approximately 43% of a copolymer of- 65% butadiene.-1,3 and 35% acrylonitrile, in such, proportions that there is present 60% of the; resinous. styrene-acrylonitrile. copoly-mer and 40% of the butadiene-acrylonitrilecopolymer." The. Buna N. latex was prepared fromthe follow-- ing recipe:

Parts by weight This recipe is polymerized at 40' C. for SQhours' passed at the rateof 60-feet perminute'through the, nip 1 of a mirror-finished chromium-plated.- calender: rolls and a; compressedcottonesurfaced i calender roll with the coated surface of the paper in contact with the chromium-plated roll which is heated to a temperature of 120 C. The paper is allowed to pass half way around the chromiumplated roll and is then stripped therefrom by taking it off in a horizontal plane. The resulting paper has an extremely high gloss and exhibits good resistance to moisture vapor transmission. lt is flexible and when sections thereof are stacked under 1 pound per square inch pressure at 170 F. no blocking occurs. Where the paper has been printed with colored inks before applying the coating, the brilliancy of the inks is greatly enhanced by the superposition of the glossy coating and upon exposure of coated samples in the Fadometer for 7 days (which is equivalent to about 7 months in the sunlight), the extent of fading of the inks was very materially reduced, apparently because the gloss reflects the injurious light rays.

The product of my invention is distinguished by its extremely high gloss. In fact the brilliancy of the coated product of my invention exceeds that of any coated paper with which I am familiar the coating of which is laid down from a coating composition. The brilliancy is so great that it cannot be measured upon the present-day glossometer. The only way of obtaining a gloss approaching the gloss of my coated product is to laminate cellophane or similar transparent foil to paper, but my product is not to be compared with such a laminated product since in my product the extent of solids application is much less than could be approached by a laminating process, and moreover in my product the film is laid down directly from a coating composition and is a hot calendered deposit in contrast to a preformed foil. My coating is formed in situ in contact with the paper as distinguished from a product made by laminating a preformed foil to paper.

The product of my invention is also dlstinguished, as mentioned above, by the exceedingly small amount of solids applied to the paper which is in marked contrast to the heavy applications of coating materials which have been considered minimum in the prior art. The product is also distinguished by the small absorption of the coating into the paper, the absorption being just sufficient to efiect tenacious adherence of the glossed film to the paper but insuflicient to effect impregnation of the paper surface with theresin of an extent which would objectionably increase the cost of the resin or interfere unduly with the flexibility of the paper. The product of my invention is also distinguished by its high resistance to moisture vapor transmission. In a standard test, the glossed paper of my invention allows less than grams of water per 100 square centimeters of surface exposed at 90 F. to an atmosphere of 95% humidity to be transmitted in 24 hours. If the paper is pre-treated with a dilute dispersion as previously described so as to reduce still further penetration of the aqueous dispersion into the paper, the resistance to moisture vapor transmission is increased to such an extent that not more than 2 or 3 grams of water per 24 hours per 100 square centimeters of exposed surface are able to pass in such a standard test.

The product of the present invention is believed to be completely different from any glossed paper product ever heretofore made. If the resinous polymer were applied in the molten state to the paper, it would penetrate into the paper thereby giving rise to an impregnated paper not comparable to the product of the present invention. A product made by lamination of a foil to paper is not comparable with the product of the present invention because it is impractical by the lamination method to apply a preformed film of the thickness contemplated by the present invention. Furthermore, a laminated foil is subject to separation, particularly when the paper is subjected to moisture. Where the resinous polymer is applied in the form of a solution in an organic solvent, excessive penetration of the resin into the paper cannot be avoided and a totally different product results. My product is unique in the small amount of material applied and is also distinguished by the fact that the coating is manifested as a surface film rather than one which penetrates into the paper to such an extent as to decrease the flexibility of the paper. However the coating of my product is tenaciously adherent to the surface of the paper as illustrated by the fact that if pressure sensitive tape is pressed firmly down upon the glossed surface of the paper of my invention and then pulled suddenly therefrom the paper is actually split and is torn away but no separation of the glossy coating from the surface of the paper occurs. In other words, the bond between the glossy coating of my invention and the paper is considerably greater than the bond between the various portionsof the paper itself.

It should be explained that the term continuous as used herein does not necessarily mean that the film is free from pinholes, but rather denotes that the polymer particles have been merged into one another in the glossing step to form a continuous structure. Thus, generally speaking, the glossed films of my invention do not begin to exhibit complete freedom from pinholes until a level of approximately 1 lb. of polymer per 1000 square feet of coated surface, and manifest freedom from pinholes from that weight of coating up. Similarly, the term discontinuous does not necessarily denote the presence of pinholes, because the film as laid down before glossing is free from pinholes when the percentage of butadiene-acrylonitrile rubbery copolymer ranges from 45 to 50% by weight based on the sum of the rubbery copolymer and the resinous styrene-acrylonitrile copolymer; however, in such a film the polymer particles are not merged together to form a continuous homogenous structure. Those skilled in the art will readily appreciate that freedom from pinholes and continuity of structure are not necessarily synonymous.

From the foregoing description many advantages of the product of my invention will be obvious to those skilled in the art. It will be seen that the present invention makes available to the art for the first time a glossed paper'product having an extremely high brilliance and good moisture vapor transmission resistance at a level of solids application which is such that the product is commercially feasible in such applications as glossed colored advertisements in magazines and containers for almost any type of product where a paper having a high gloss is desirable. The coating of the present invention can be readily applied over ordinary printing or lithographing with any color of ink and serves to enhance greatly the brilliancy and attractiveness of the printed or lithographed sheet. Many other advantages of the product of my invention will be obvious to workers in the art.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. As a new article of manufacture, paper in sheet form having on a surface thereof a thin continuous flexible transparent coating of polymeric material selected from the group consisting of a resinous copolymer of styrene and acrylonitrile in proportions of from 65 to 80 per cent by weight of styrene and correspondingly from 35 to 20 per cent by weight of acrylonitrile and mixtures of from 50 to 95 per cent by weight of said resinous copolymer and correspondingly from 50 to per cent by weight of a rubbery copolymer of butadiene-l,3 and acrylonitrile, said coating being manifested as a highly glossed film so tenaciously adherent to the surface of the paper that when pressure sensitive adhesive tape is pressed firmly upon the coated surface and then pulled suddenly therefrom the paper is split and no separation of the coating from the surface of the paper occurs, the amount of said coating ranging from 0.1 to 3.0 pounds of polymeric material per 1000 square feet of coated surface, said coating being a hot calendered film formed in situ of the solids deposited by drying from an aqueous dispersion of said polymeric material.

2. As a new article of manufacture, paper in sheet form having on a surface thereof a thin continuous flexible transparent coating of a mixture of a resinous copolymer of styrene and acrylonitrile in proportions of from 65 to 80 per cent by weight of styrene and correspondingly from 35 to 20 per cent by weight of acrylonitrile, and a rubbery copolymer of butadiene-1,3 and acrylonitrile, the relative proportions of said resinous copolymer and of said rubbery copolymer ranging from 50 to 95 per cent by weight of said resinous copolymer and correspondingly from 50 to 5 per cent by weight of said rubbery copolymer, said coating being manifested as a highly glossed film so tenaciously adherent to the surface of the paper that when pressure sensitive adhesive tape is pressed firmly upon the coated surface and then pulled suddenly therefrom the paper is split and no separation of the coating from the surface of the paper occurs, the amount of said coating ranging from 0.1 to 3.0 pounds of said copolymers per 1000 square feet of coated surface, said coating being a hot calendered film formed in situ of the solids deposited by drying from an aqueous dispersion of said resinous and rubbery copolymers.

3. As a new article of manufacture, paper in sheet form having on a surface thereof a thin continuous flexible transparent coating of polymeric material selected from the group consisting of a resinous copolymer of styrene and acrylonitrile in proportions of from 65 to 80 per cent by weight of styrene and correspondingly from 35 to 20 per cent by weight of acrylonitrile and mixtures of from 50 to 95 per cent by weight of said resinous copolymer and correspondingly from 50 to 5 per cent by weight of a rubbery copolymer of butadiene-1,3 and acrylonitrile, said coating being manifested as a highly glossed film so tenaciously adherent to the surface of the paper that when pressure sensitive adhesive tape is pressed firmly upon the coated surface and then pulled suddenly therefrom the paper is split and no separation of the coating from the surfaceof the paper occurs, the amount of said coating ranging from 0.1 to 3.0 pounds of polymeric material per 1000 square feet of coated surface, said coating being a hot calendered film of the solids deposited by drying from an aqueous dispersion of said polymeric material, the extent of penetration of the solids of said dispersion into the paper not exceeding 20% by weight of the polymeric material content of said dispersion, said coating exhibiting a resistance to moisture vapor transmission equal to not over 5 grams of water per 100 square centimeters per 24 hours when exposed at F. to an atmosphere of at least relative humidity.

4. As a new article of manufacture, .paper in sheet form having on a surface thereof a thin continuous flexible transparent coating of a mixture consisting essentially of a resinous copolymer of approximately '70 per cent by weight of styrene and 30 per cent by weight of acrylonitrile and a rubbery copolymer of butadiene-1,3 and acrylonitrile, the relative proportions of said resinous copolymer and of said rubbery copolymer ranging from 50 to 95 per cent by weight of said resinous copolymer and correspondingly from 50 to 5 per cent by weight of said rubbery copolymer, said coating being manifested as a highly glossed film so tenaciously adherent to the surface of the paper that when pressure sensitive adhesive tape is pressed firmly upon the coated surface and then pulled suddenly therefrom the paper is split and no separation of the coating from the paper surface occurs, the amount of said coating ranging from 0.1 to 3.0 pounds of said copolymers per 1000 square feet of coated surface, said coating being a hot calendered film formed in situ of the solids deposited by drying from an aqueous dispersion of said resinous and rubbery copolymers and being bonded directly to the surface of the paper by absorption thereinto of not over 20 per cent by weight of the polymeric material contained in the dispersion.

WILLIAM W. COWGILL.

No references cited.

Claims (1)

1. AS A NEW ARTICLE OF MANUFACTURE, PAPER IN SHEET FORM HAVING ON A SURFACE THEREOF A THIN CONTINUOUS FLEXIBLE TRANSPARENT COATING OF POLYMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF A RESINOUS COPOLYMER OF STYRENE AND ACRYLONITRILE IN PROPORTIONS OF FROM 65 TO 80 PER CENT BY WEIGHT OF STYRENE AND CORRESPONDINGLY FROM 35 TO 20 PER CENT BY WEIGHT OF ACRYLONITRILE AND MIXTURES OF FROM 50 TO 95 PER CENT BY WEIGHT OF SAID RESINOUS COPOLYMER AND CORRESPONDINGLY FROM 50 TO 5 PER CENT BY WEIGHT OF A RUBBERY COPOLYMER OF BUTADIENE-1,3 AND ACRYLONITRILE, SAID COATING BEING MANIFESTED AS A HIGHLY GLOSSED FILM SO TENACIOUSLY ADHERENT TO THE SURFACE OF THE PAPER THAT WHEN PRESSURE SENSITIVE ADHESIVE TAPE IS PRESSED FIRMLY UPON THE COATED SURFACE AND THEN PULLED SUDDENLY THEREFROM THE PAPER IS SPLIT AND NO SEPARATION OF THE COATING FROM THE SURFACE OF THE PAPER OCCURS, THE AMOUNT OF SAID COATING RANGING FROM 0.1 TO 3.0 POUNDS OF POLYMERIC MATERIAL PER 1000 SQUARE FEET OF COATED SURFACE, SAID COATING BEING A HOT CALENDERED FILM FORMED IN SITU OF THE SOLIDS DEPOSITED BY DRYING FROM AN AQUEOUS DISPERSION OF SAID POLYMERIC MATERIAL.