US2214564A - Coated paper and method of making the same - Google Patents

Description

Patented Sept. 10,1940 I l' I I l I I UNITED STATES PATENT OFFICE o i 2,214,564

COATED PAPER AND METHOD OF v MAKING THE SAME I William J. Montgomery and Donald B. Bradner, Hamilton, hio,- as.signors to The Champion Paper'and Fibre Company, Hamilton, Ohio, a corporation of Ohio No Drawing. Application anuary 26, 1938, I sem naisaqu This invention relates to coated paper for. the procedures described in the aforementioned printing and lithographic purposes, and partic- Bradner patent or the Bradner and Montgomery: ularly to paper having a cast" surface produced, patent may be employed. That is, the coating by the processes described in Patent No. 2,029,273, composition may be continuously applied to a 6 issued January 28, 1936 to thepresent applicants, traveling web of paper and subsequently dried and in Patent No. 1,719,166, issued July 2, 1929 or hardened in contact with a non-adhering fintoDonald'B. Bradner, one of, the present appliishing surface such as for instance a mirror-pol! cants. It, also relates to processes of producing ished chromium plated drum or belt, or the coatsaid paper... I I I ing may be applied to the polished surface and i 10 The paper oi! the present'invention is vemitransferred to the traveling web. The present nently adapted to the production 01 canand bot- I inventionrelates to the nature of the cast coated tle labels, of cigarette and other packages, for surface on thepaper. The'cast surface coating fancy candy box wrappings, for carton liners, for on our new paper ordinarily comprises a mixture book jackets, magazine covers, advertizing foldof adhesive and filler, and is characterized by ers and other uses. I I what the coated paper industry would consider The most highly finished grades of fsupercalan undesirable excess of adhesive. endered and brush-finished coated papers have. For example, two samples of coated paper insuflicient gloss for present-day demands, as is made with cast surface in accordance with the evidenced bylthe. extensive, employment of varprocedure described in the Bradner patent and .7

M nish and lacquer, and the general useof Cellosubstantially identical except for the proportions phane, either alone or pasted over printed paper. of filler (clay) and adhesive (casein) in thecoat--v The above designated Patent No; 1,719,166-deing were tested on the Bausch and Lomb gloss scribes the new cast coating process as it is pracmeter in comparison with two similar samples ticed in applying to paper stock typical mineral having, respectively, the same coating composill coating compositions such as have beenemployed tions, but made according to the usual methods for many years for making coated paper. The and supercalendered in accordance with the usual application of such coatings by the so-called p oc d e i e art t O ta n ah gh 81085- The "Bradner" process producesa coating of outresults were as follows:

, standing smoothness and gloss; a coating great ly superior in these characteristics to coatings of E Super-;

similar composition when applied by any previously known method. Contrary, however, to. what would be expected, these high gloss, ex: ceptionally smooth 'cast" coatings of the fore A B A B u; mulae given in the Bradner patent are not as I i 01 t ts s3 a 83. so suitable for printing with gloss ink as coatings exit-$303? 17 :8 17 70 oi the same composition when applied and supermbi Limb 76 94 65 calendered by the usual methods. The cast coat- I ings are more absorbent to printers ink than the Viewed at low angle illumination under the 4 supercalendered coatings. In general, the ink microscope the surface of sample B was some- 1 40 after drying has a smooth velvety appearance What S oo r than Sample which n t n with little gloss. This is an effect much sought was definitely smoother than sample A, whilst after for many purposespbut it is a dlstinct-dissample B was noticeably rougher than A. Sam-L advantage when a gloss ink 'eflect is desired'beple B printed in gloss ink presented on drying cause the mirror finish is destroyed wherever it a gloss substantially equal to the gloss. ofthe 5 has been touched with ink, the dullness of the? paper, indicating very little absorption of the ink being accentuated by the greater gloss of ink by the paper, and the difference in ink abthe unprinted areas. I sorption between samples A and B was much The primary object of. the present invention greater than between A and 3'. I I I is to provide a low cost mass production paper The ratio of adhesive to filler required for 50 which when printed with suitable ink will have the p'resentpurpose varies with the character a brilliant gloss on both printed and unprinted of the filleremployedi It' is well recognized in portions without any subsequent varnishing or the manufacture of coated paper, that is, pa

other operation. r per carrying supercalendered coatings of the Incarrying out-the present invention one of composition desig'nated as mineral coatings" in 55 hesive content the more difficult it becomes to smooth out the coating in the supercalenders.

The one property which determines the printing quality of coated paper above everything else is its degree of smoothness. In making'the best grades of supercalendered coated paper only enough adhesive is used to assure absence of picking or lifting on the press, for the reason that excess adhesive in the coating, other conditions being the same, impairs the gloss and smoothness imparted by the calendering. With the Bradner process the use of excess adhesive has the opposite effect. It enhances the gloss obtainable and improves the smoothness. The decreased absorbency makes it possible, by the use of gloss inks, to secure a gloss on the printing ink commensuratewith the gloss on the paper itself. The decreased absorbency also reduces finger-marking which is otherwise especially dis-v figuring in the case of brightly colored high-gloss by laboratory tests.

magazine covers, box covers, labels, etc.,

tractive material. v

By the expression excess adhesive we mean an excess over what would be commonly employed by an experienced paper-maker to insure the adhesion of the coating to the paper. This insurance'involves a factor of safety over what might be the absolute minimum as would be determined Different batches of clay and other fillers supposedly of the same composition vary from one another in the amount of adhesive required to prevent picking of the coating in the printing operation. It is common practice, therefore, in making up the formulae for coating compositions to designate the amount of adhesive which experience has indicated ,will insure a. proper adhesionof the coating to the paper stock,

with any lot of designated filler and. under any printing conditions.

Although a comparatively small excess of adhesive decreases the ink absorption of the cast coating, enhances its gloss and improves its smoothness, it is possible to increase theproportion of adhesive and decrease that of filler to any" degree required to' yield the results desired in any particular case. To secure opacity in coatings containing 30 per cent or more of adhesive it may be necessary to use in the filler a pigment of high refractive index such as zinc oxide, zinc sulphide,

lithopone, or titanium oxide. For example, a

. coating composition of 40 per cent calcium carbonate, 10 per cent titanium. oxide, and 50 per cent casein when cast upon the paper stock, produces a high-gloss opaque coating ,with low ink absorption.

In some cases a transparent coating is desirable, and in such cases if fillers havinga refractive index nearly equal to that of the desired adhesive such as clayv and casein) are used a coating may contain as much as 50 per cent or more of mineral filler and still be substantially trans: parent.

In the specific examples of coating compositration of oil-base printing inks.

for which cast surface paper is a particularly atr tions employed in'carryingbut the present invention whichwe have given above, only casein is mentioned as the adhesive. Other adhesives known in the art may be used in lieu of casein with like results. For, example, a coating compo sition consisting of 30 parts of blame fixe, 30 parts of clay, and Y40 parts of coating starch when cast onthe surface of suitable paper stock in accordance with the processor the Bradner patent produces a finish of high gloss and smoothness and with a high resistance to pene- Another. adhesive that may be used tive wrappers or the like. For example, a coating composition consisting of,78% shellac, 4%-

sulph onated castor oil, and 18% dyein aqueous ammonia dispersion, ,whencast on asuitable paper stock produces a wrapping paper which is of exceptional-gloss and smoothness and highly suitable for printing with gloss inks.

a 7 is shellac. Due tothe color in the shellac its use is largely a confined to coloredpaper such as used for decora- For colored coatings dyes, colored pigmentsfor mixtures of dyes and pigments may be employed.

The above mentioned dyes, fillers, and pigments are ordinarily applied in aqueous dispersion; However, the present invention is not limited to;

the use'of aqueous suspensions; organic solvents may be used; also thermoplastic 'gumsor resins 1 '30, surface is obtained by cooling in contact with may be used, in which case the required cast' thenonadhe'ring finishing surface, and the solvent or suspending liquid may be dispensed: with entirely. Ammonium stearate in the quantity specified in the above mentioned Montgomery and Bradner patent may be used with advantage in the examples given above to facilitate the casting operation. a

In the foregoing specification we have referred to the coatings produced by the Bradner process as presenting a gloss finish. The paper embodying the invention of the present application is not, however, limited to paper presenting a glossfinish. Either the gloss-finish or the matte flnish of the Bradner process may be emplo' yed for thepaper of the present application. Matte-finish paper is frequentlyused for" printing withf" gloss inks, pleasing artistic effects and contrasts being thereby secured. Also the paper of the present invention possesses superior printing qualities in the'matter of definition, uniformity,

etc., and presents an enhanced smoothness over' paper coated with the customary mineral coat-o ings'of the art such as referred to in theB'radner patent.

It is alsoto be formulae given above are intended to be by way of examples and not as limitations, and that the term filler is used in the appended claims to include mineral fillers, pigments, dyes, and othersubstances incorporated in paper coating compositions. I h

'I'heexpression cast surfaced coating is used which has beenset from a plastic condition in 7 56 understood that the specific in the appended claims to, designate -a coa ting contact with a solid, nonadhering casting surface described in the patents to Bradner, No. l,'719,166,

Or to Montgomery and Bradner, No. 2,029,273, 3

so that the surface of the coating has substan-' tially the same finish as thecasting surface itself w We claim: a 1. Printing paper ing which comprises a major and a'n'iinor portion of filler.

carrying a cast surface coatportion of adhesive f 2. The process of manufacturing coated printing paper which comprises applying to paper a v coating composition comprisingfiller and adhesive, said adhesive being present in an amount greater than 30% by weight of the coating composition calculated on a dry basis and imparting to the surface of the coating material a high degree of smoothness by causing the coating to harden in contact with a smooth, non-adhering surface. I

3. Process of manufacturing coated printing paper which comprises applying to paper a coating composition comprising filler and adhesive, said adhesive being present in an amount greater than 30% by weight of thecoating composition calculated on a dry basis, contacting the coated paper with a non-adhering finishing surface while the coating is in a plastic condition and rendering the coating non-plastic while in contact with said finishing surface.

4. The. process of claim 2 in which the coating composition comprises a mineral filler and an adhesive.

5. Printing paper carrying a cast surfaced adhesive and mineral filler, the mineral filler be- I ing in amount less than 70% by weight of the total coating calculated on the dry basis.

- 7. The paper of claim 6 in which the adhesive used is casein 8. The paper of claim 6 in which the mineral filler is of high refractive index as compared with the refractiveindex of the adhesive.

9. Process of making cast surfaced coated paper which comprises applying to paper a coating composition-comprising an aqueous dispersion containing shellac, the shellac comprising more than 30% by weight of the total coating calculated on the dry basis, and imparting to the surface of the coating material'a high degree of smoothness by drying the coating in contact with a smooth, nonadhering surface.

WILLIAM J. MONTGOMERY. DONALD B. BRADNER.