A predecorated gypsum wallboard and the method of manufacture wherein a protective base coat is applied on the face paper by a rotogravure printing of the protective coat with minute openings very closely spaced throughout the coating, as by printing the coat in the form of reasonably uniformly sized tiny dots with about 1000 to about 100,000 dots per square inch, a decorative coat is applied over the base coat, gypsum wallboard is formed with the coated surface of the paper on the outside face, and the newly formed wallboard, when hardened, is dried by heating and removing water from the gypsum core through the still porous coated paper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
These and other objects and advantages of the invention will be more 
readily apparent when considered in relation to the preferred embodiments 
of the invention as set forth in the following specification. 
In accordance with the invention, gypsum wallboard paper, of about 0.005 to 
0.020 inch thickness, is first manufactured using known Fourdrinier or 
cylinder type paper machines. The quality of the predecorated gypsum board 
made by the invention will be, in part, dependent on the smoothness of the 
front surface of the face paper, with a smoothness of from about 60 to 
about 400 Sheffield units being satisfactory for most designs, and about 
60 to about 200 Sheffield units being essential for high fidelity designs, 
such as wood grain patterns. The lower the Sheffield units for any paper, 
and thus the smoother the paper, the better it will be for use in the 
invention. 
The porosity of the paper to be predecorated preferably has a porosity of 
about 25 to 70 seconds, when tested using a Gurley Densometer, in 
accordance with TAPPI Standards T460m-49, however less porous paper, up to 
100 seconds or more, can still be used to make predecorated front paper in 
accordance with the invention. More porous paper, as fast as about 10 
seconds, can also be successfully used. Considering porosity alone, the 
more porous the paper is the better for making gypsum board. 
The Cobb value of the paper, tested on the front surface, in accordance 
with the general test outlined by TAPPI, should be no greater than 1.8 
grams. The consistent brightness and color of the paper can be of 
importance in maintaining a consistent product, with each predecorated 
board of a given design matching all other boards of the same given 
design. 
The front surface of the face paper is, first, printed, by the rotogravure 
process, with a plurality of closely spaced minute dots or extremely 
narrow, closely spaced parallel lines, when viewed through a microscope, 
forming a coat of a thermosetting aqueous latex emulsion having 
substantially throughout minutely closely spaced, minute openings or 
voids, which open areas may be continuous with discontinuous minute areas 
of base coat, or discontinuous minute areas surrounded by continuous or 
adjoined areas of base coat, or a combination of the two. This 
thermosetting aqueous latex emulsion coat may be either clear or tinted. 
It is preferably disposed uniformly throughout substantially all of the 
face paper front surface. This coat of separated minute dots or lines or 
the like of thermosetting aqueous latex emulsion, immediately after 
application, normally flows to a limited extent prior to its drying, 
forming a base coat, which when dried may be in the form of minute 
separated dots or lines or in the form of minute interconnected dots with 
a great plurality of openings resulting from the emulsion of the dots or 
lines being insufficient to completely coat and close any substantial 
area. These openings are spaced apart at average distances of between 0.1 
inch and 0.001 inch, and preferably about 1/32 inch to about 1/320 inch, 
relatively uniformly throughout the base coat. 
The viscosity of the thermosetting aqueous latex emulsion is important in 
order to be able to deposit a proper amount by a rotogravure process onto 
the face paper front surface. Viscosity determination, by a General 
Electric Zahn viscometer method, should indicate a viscosity of about 15 
to about 30 seconds, when measuring the time for a measured amount of 
emulsion, contained in a #2 Zahn cup, to flow out through the orifice in 
the bottom, a test method commonly used in the ink and paint industry. 
Plain water, tested in a #2 Zahn cup, has a viscosity of about 15 seconds, 
and, thus, about 15 seconds is the minimum viscosity of a suitable 
thermosetting aqueous latex emulsion. The maximum permissible viscosity is 
that viscosity at which the emulsion can still be deposited by a 
rotogravure process. 
Preferably the base coat is a self-reactive, cross-linking copolymer, 
activated by heat after having a second design coat printed over the base 
coat. This heat activation, to cure the base coat, can be delayed until 
after the paper has been used to form gypsum wallboard, at which time 
curing is carried out in the wallboard dryer, as the wallboard is dried, 
and excess water in the set gypsum core is removed. The curing forms a 
tough, hard, durable, non-blocking coating, from a coating which had no 
durability before curing. 
The thermosetting latex base coat may be a self-reactive acrylic, or an 
acrylic-vinyl copolymer. Examples of suitable thermosetting acrylic latex 
emulsions include Amsco RES 3112 sold by Union Chemicals Division of Union 
Oil Company of California as number 8262, and a Clear Gloss Aqualure sold 
by Glidden Coatings and Resins Division of SCM Corporation as number 
847-C-02109. Prior to use, the Clear Gloss Aqualure must be catalyzed in 
the ratio of one part by weight of Catalyst Converter 297-C-12128 to 
thirteen parts by weight of Clear Gloss Aqualure. 
The base coat is applied at a rate of about one to three pounds of 30% 
solids emulsion per thousand square feet of paper, or about 1/4 to one 
pound of solids per thousand square feet of paper. This emulsion is 
applied to a continuously moving web, about four feet wide, of face paper, 
by the rotogravure process, using a chromed steel roll rotary press, 
printing the emulsion in the form of minute shapes minutely spaced apart 
substantially throughout the whole front surface of the face paper, with 
the exception of an uncoated edge portion at each side, of about 5/8" to 
3/4" width. 
If minute dots are employed, they are of a size such that there are between 
about 1000 and 100,000 spaced apart dots per square inch, preferably from 
about 3000 to 40,000 spaced apart dots per square inch, such as about 55 
to 200 dots per lineal inch in each of two perpendicular directions, for 
example. The dots are formed by the emulsion being placed in minute holes 
extending into the rotogravure printing roll and deposited on the paper 
surface in a manner similar to rotogravure printing of ink solutions. The 
holes, and the resultant dots may be of any shape, circular, square, 
oblong, etc., so long as the holes will retain the emulsion until the 
paper is contacted and the emulsion will then deposit on the paper, at the 
desire rate of application. Typically the holes may average about 0.005 
inch in diameter and between about 0.001 and 0.002 inch deep. If a pattern 
of narrow lines are employed, there should be about 30 to about 300 lines 
per inch. 
As an example, the rotary press cylinder may have holes or depressions of a 
generally semi-spherical shape, arranged in diagonal rows, 45.degree. in 
each direction from a line circumscribing the circumference of the 
cylinder, with 120 holes per inch in each diagonal direction, and thus 
14,400 holes or depressions per square inch. The holes or depressions are 
separated by lands between depressions which extend in a generally zig-zag 
manner circumferentially around the cylinder, resulting from the diagonal 
arrangement of the rows of depressions, and from the narrow shallow groove 
adjoining depressions lying adjacent to each other in circumferential 
directions. This gravure print cylinder is referred to as having a QCH 
cell configuration in the rotogravure printing industry and is a preferred 
cell configuration in the present invention. 
The base coat is dried, but not cured, immediately and the base-coated 
paper is fed to a plurality of, from about 2 to about 8, printing rolls, 
each of which prints a design onto the base-coated, but not cured, paper 
using what are referred to as high-binder durable inks. The base coat, 
once cured, protects the paper, and the durability of the inks protects 
the inks. 
Each printing roll applies a portion of a design, each in different colors 
or different shades of a color, preferably in small blotches, i.e. small, 
irregular spots or marks using the high-binder inks. The high-binder inks 
are a mixture of pigment, a thermoplastic resin, and a solvent, all of 
which preferably are relatively non-reactive with the base coat. 
The base-coated and printed front paper is then either fed directly to a 
machine for forming gypsum wallboard, or wound into a roll temporarily, to 
subsequently be unwound and fed to a wallboard machine. When fed to the 
wallboard machine, the face paper is conveyed, front surface down, and a 
settable gypsum aqueous slurry is disposed on the face paper back surface. 
A continuous web of back paper is then disposed over the gypsum slurry and 
the edges of the face paper are wrapped up and around the edge of the 
slurry, as the composite is formed into a flat thin board form. 
The back paper may be of any known sultable type of gypsum board paper, 
preferably generally similar to the basic uncoated face paper, 
particularly in weight and porosity, but of lower cost paper fiber raw 
material, less brightness and less smoothness, these characteristics being 
of less importance on the gypsum board back surface. 
After forming, the gypsum boards of the invention are cut into suitable 
lengths and conveyed through a high temperature board dryer. The base coat 
is cured in the board dryer, forming the very durable coating essential in 
predecorated wallboards. A period of about 5 minutes at 300.degree. F. or 
a period of about 30 minutes at 200.degree. F. are typical of the amount 
of heat required for a satisfactory cure of a preferred thermosetting base 
coat. 
Having completed a detailed disclosure of the preferred embodiments of our 
invention so that those skilled in the art may practice the same, we 
contemplate that variations may be made without departing from the essence 
of the invention or the scope of the appended claims.