US1863731A - Coated paper and method of making the same - Google Patents

Description

Patented June 21, 1932 ARLIE W. SCHORGER, F MADISON, WISCONSIN, ASSIGNOR, BY MESNE ASSIGNMENTS,

FREEPORT, ILLINOIS, A CORPORATION OF TO BURGESS CELLULOSE COMPANY, OF DELAWARE TED STATES PATENT OFFICE;

Y COATED PAPER AND METHOD OF MAKING THE No Drawing. Continuation of application Serial No. 335,390, filed January 26, 1929. This application filed November 12, 1929. Serial No. 406,724.

This invention relates to a coating for paper and especially stereotype mats.

This application is a continuation of my copending application Serial No. 335,390, filed January 26, 1929.

The objects of my invention are to produce a smooth surface so that fine cuts reproduce well; to bind the surface fibers together so that they will not be loosened by mechanical action as when stereotype plates" areremoved; and to facilitate release of metal after stereotype metalis cast. Although my coating is especially useful for stereotype mats, it may also be applied to other paper or fibrous products.

Various coatings have been used for stereotype mats but none have proved entirely satisfactory. I have discovered that a coating will possess superior qualitiesif it contains certain ingredients which have not been used heretofore to the best of my knowledge. My preferred formula comprises a water solution or suspension which includes thin boiling starch, yellow dextrin, clay, bentonite, a salt of a higher fatty acid, and a preservative, such as otassium chromate,

but I believe that the atty acid salt is the ing and the surface also becomes too' dense i and hard. As examples of fatty'acids salts may be mentioned the caustic alkali, alkaline earth, and heavy metal salts of palmitic, stearic, oleic acids, etc. The saltsof'the individual acids may be used, or their mixtures. The salts of the higher fatty acids may be used also admixedwith the metallic salts of abietic and similar resin acids. The. term fatty acid salt will be used to include any one of the salts mentioned above or their mixtures, and is not confined to the fatty acids mentioned. V

The following preferred formula may be boiling starch de ending on fluidit varied over a considerable range to suit the specific requirements of the user:

Thin boiling starch 2 lbs.

Yellow dextrin 4 lbs.

Clay (kaolin) 7. 5 lbs.

Bentonite 5 lbs.

Salt of a higher fatty acid odium stearate') 325 lbs. (0.1-0.5 lbs.)

Potassium chromate 70 grams Water 11 gallons All the constituents except the fatty acid salt are mixed thoroughly in the dry condition so that the finished "product will be" free from lumps of bentonite. Add gallons of water and boil until the suspension does not increase in thickness. Actual boiling for 15minutes is usually'ample. A soluble fatty acid salt such as sodium stearate is dissolved in 1 gallon of hot water, and the two solutions after some cooling are mixed thoroughly. The coating solution has a consistency approximating that of a paint. The coating when cold is applied to the paper or mats by means of a brush or coating machine. The fatty acid salt'is preferably kept below 1% (dry fatty acid) of the total mixture.

The yellow dextrin is used on account of its low viscosity since the latter permits it to penetrate the surface of the mat and bind the fibers together. It is preferred over the white dextrin which is more gummy and possessed of low penetrability. The percentage of yellow dextrin may vary preferably from '3 to 5 percent of the coating mixture. 1 also believe that the use of yellow dextrin in stereotype mat coatings is novel. 7

,. The starch has 'a'high viscosity and low penetrating power. It gives body to the coating and cements'the clay together. The percentage may vary over a considerable range. Thin boiling starch is prepared by heating starch with small amount of acid or oxidizing agent at 100 F. There is a partial hydrolysis of the starch without bursting of granules. It is sold as 20, 30, 60, thin after boiling. White extrin is practica ly .90 thin boiling starch.

Clay such'as kaolin is used for the purl pose of filling the depressions in the paper or stereotype mat and producing a smooth surface. 'The amount may vary drated considerably. 'Bentonite, a colloidal cla is used for two purposes-to give body to t e coating so that t will not settle readily; and when used on vent molding by fungi. Other chemicals,'

ing and cooling of the constituents,

.rapid stirring,

such as sodium benzoate or boric acid may be used for that purpose.

If it is desired to use the insoluble salts of the alkali earths and heavy metals a solution of the alkali metal salts of the fatty acids, such as sodium oleate, sodium-stearate, etc. ma be treated with a salt of the desired meta suc as zinc sulfate, magnesium sulfate, alum, calcium chloride, etc., as is well known to those skilled in the art. The precipitation is performed-preferably after mixing, heatusing in order that the insoluble fatty acid salt formed will be finely and uniformly distributed. a

For stereotype mats bentonite or its equivalent should be used in the coating. For paper other than mats the bentonite or its neeava prising an insoluble salt of a higher fatty acid and bentonite.

10. A stereotype mat having a surface coating of a mixture containing'a salt of a higher fatty acid in an amount of less than 5 percent (dry basis) of the solid ingredients ofsald coating.

of a higher fatty acid and-bentonite in suit-. h I

able proportions for use as a coating on the impression surface of a stereotype mat.

tonite in suitable proportions for use as a coating on the impression surface of a stereotype mat. 4

. n testimony whereof I aflix m signature. ARLIE W. SC ORGEB.

equivalent may be replaced entirely or in part by clay in addition to the clay specified. I claim: 1. Themethodofmakin a pervious surface on a stereot mat whi comprises facing the mat wit a water suspension containing a salt of a higher fatty acid and ahydrate mineral which loses its water on scorching, and then scorchin the mat.

2. The method 0 making a-pervious surface on a stereotype mat which-comprises fac-. ing the mat with a water sus nsion containing a salt of a hi her fatty acid and bentonite, and then scorc ing the .mat.

3. A stereoty prising a salt 0 a low dextrin.

4. A stereotype mat having a coating comprising a salt of a higher fatty acid, yellow dextrin, a thin boiling starch, clay, and a pre-- servative. v

5. A stereotype mat having a coating containing'yellow dextrin as one of the ingredients.

6. A stereotype mat having 'a coating comprising asalt of a higher fatty. acid, yellow higher fatty acid and yeldextrine-and thin boiling starch.

7. 'A stereotype mat having a coating com. prising a salt of a higher fatty acid, yellow dextrin and clay.

8. A stereotype mat having a coating comrising" a salt of a ntonite.

9. A stereotype mat having a coating commat having a coating coinhigher fatty acid and 13. A coating solution comprisingan in- I soluble salt of a higher-fatty acid and benico I Ill lac