Pad coating for carbonless paper products

A pad coat for a carbonless paper product is provided. The pad coat comprises a binder; a pigment; and an adhesive component capable of preventing a fan-out padding adhesive from substantially penetrating and wetting a surface of the carbonless paper product. In an embodiment, the binder is a starch. In an embodiment, the pigment is chosen from the group of materials consisting of alumina trihydrate, calcium carbonate, clay, calcined clay, and silicates. In an embodiment, the adhesive component is a fluorinated compound. Preferably, the pad coat is mixed with water to make a solution, the solution comprising approximately 5 to about 60% solids and approximately 40 to about 95% water.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
The present invention relates generally to carbonless paper products. More 
specifically, the present invention relates to the pad coating for 
carbonless paper products. 
B. The Prior Art 
Carbonless paper products are known in the art. These products function to 
afford one the ability to make "carbons" or duplicates of a document, bill 
of lading, invoice, or the like, without the need for carbon paper. As is 
clearly evident, carbon paper has several disadvantages. These 
disadvantages include the fact that it is a cumbersome, sometimes 
difficult, process to insert carbon paper between the sheets of paper upon 
which a duplicate is to be made and the process of so inserting the carbon 
paper and removing same can be messy. To resolve some of the disadvantages 
inherent with carbon paper, carbonless paper was developed. 
Briefly, carbonless paper typically includes a paper substrate upon which a 
front coating (hereinafter "CF") and a back coating (hereinafter "CB") are 
coated on respective sides of a paper substrate. The CF and CB have 
compositions such that upon a mixing of the CF and CB a mark is generated. 
Accordingly, in constructing a carbonless paper product, the sheets of 
paper are oriented so that the sheets of paper on which a duplicate copy 
is to be made all include, on a front surface thereof, a CF layer. This CF 
layer is located in juxtaposition to a CB layer that is located on the 
back surface of all of the sheets of paper from which a duplicate is to be 
generated. An inter mixing of the CF and CB layer is created by the 
exertion of a sufficient force on a front face of the paper. This results 
in the generation of a mark, on the underlying layers of the carbonless 
paper, that corresponds to the mark made on the original front surface of 
the top sheet. 
Carbonless paper has especially enjoyed commercial success in applications 
where two or three duplicates of a form are required. Such forms include, 
for example, bills of lading, invoices, credit card receipts, and the 
like. These documents typically comprise two or more sheets that are 
secured together by some means. One of the most common ways to secure the 
sheets together is to use an adhesive coating that is coated along one 
edge of the sheets. This typically is called a fan-out padability 
adhesive. Such adhesives are commercially available from the Appleton 
Paper Co., Minnesota Mining and Manufacturing Co., and Mead Paper Co., 
among others. 
One of the disadvantages in using such an adhesive coating, however, is 
that these form sets are typically generated by the thousands and it is 
not economical to separately coat each set of sheets that define the form. 
Instead, a pad coat is utilized on at least the bottom of the last sheet 
of each set of the forms, and often on the top of the first sheet of the 
form set as well. The function of the pad coats is to prevent the 
individual sets of forms from sticking together when the fan-out 
padability adhesive is applied thereto. The use of a pad coat results in 
the individual sheets that define one form set being secured together but 
not the form sets themselves. The capacity of the last sheet of one form 
set to separate from the first sheet of a next form set is called 
"fanapart" or "padability." 
Although pad coats have been developed that provide some fanapart of the 
form sets after an adhesive is applied, these coats have not been entirely 
satisfactory. One problem is that, in many instances, the back of the last 
sheet of a form set must contain instructions, contract terms, or other 
necessary information. Accordingly, any such pad coating coated on the 
back surface of the last sheet must allow this surface to be printed 
thereon. However, some prior pad coats, when coated on a paper product, 
create a surface that has poor printability. 
Still further, it is necessary for any such pad coat to have 
characteristics such that it can coat the base paper, or paper substrate, 
through commercial production techniques. 
SUMMARY OF THE INVENTION 
The present invention provides an improved pad coat for carbonless paper 
that affords the form sets good padability when a fan-out padding adhesive 
is applied along an edge of the individual sheets of paper by conventional 
techniques. Furthermore, the pad coat provides a surface which retains the 
good printability characteristics of the paper itself. 
The pad coat of the present invention comprises: a binder; a pigment; and 
an abhesive component, i.e., a composition capable of preventing fan-out 
padding adhesive from substantially penetrating and wetting the back of 
the CF and front of the CB sheets of the carbonless form set. 
Preferably: the binder is a starch; the pigment is chosen from the group of 
materials consisting of alumina trihydrate, calcium carbonate, clay, 
calcined clay, and silicates; and the abhesive component is a fluorinated 
compound. 
In an embodiment of the present invention, the pad coating includes a 
thickener. Preferably, the thickener is chosen from the group of materials 
consisting of carboxymethylcellulose, hydroxyethylcellulose, and alginate. 
In an embodiment of the present invention, the pad coating includes a pH 
adjuster and a dispersing agent. 
Preferably, the pad coat formulation is applied to the paper as an aqueous 
dispersion. Preferably, the solution comprises approximately 5 to about 
60% by weight solids and approximately 40 to about 95% by weight water. 
Preferably, the solids comprise approximately 20 to about 80% by weight 
binder, 20 to 80% by weight pigment, and approximately 0.5 to about 10% by 
weight of an abhesive component. 
The present invention also provides an improved carbonless paper product 
comprising a paper base and a back coating comprising the pad coat of the 
present invention. 
Additional features and advantages are described in, and will be apparent 
from, the detailed description of the presently preferred embodiments and 
from the drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
The present invention provides an improved pad coat for a carbonless paper 
product. More specifically, the present invention provides a pad coat that 
prevents fan-out padding adhesive from substantially wetting and 
penetrating at least the edge of the paper base and therefore, affords 
good padability of certain sheets of the paper product after the sheets 
are secured together by a fan-out padding adhesive. 
The pad coat comprises: a binder; a pigment; and an abhesive component. 
The binder of the present invention functions to allow attachment of the 
other components to the paper, and preferably is a starch, but other 
binders, such as proteins and polyvinyl alcohol, can also be utilized. 
Such starches as corn starch, wheat starch, and potato starch have been 
found to function satisfactorily. Most preferably, the binder of the 
present invention is a hydroxyethylated corn starch. A hydroxyethylated 
corn starch purchased from Penick and Ford, of Iowa, under the name 
Penford Gum 260, has been found to function satisfactorily. 
The pigment of the pad coat composition functions, at least in part, to 
increase the ink receptivity of the pad coat. This improves the 
printability on the surface of the paper coated with the pad coat of the 
present invention. Accordingly, any pigment having good ink receptive 
characteristics can be utilized, however, preferably, the pigment is 
chosen from the group of materials consisting of: calcium carbonate; clay; 
calcined clay; silicates; and alumina trihydrate. Most preferably, the 
pigment is alumina trihydrate. An alumina trihydrate purchased from Alcoa, 
under the name Hydral 710B, has been found to function satisfactorily in 
the pad coat of the present invention. 
The abhesive component is preferably a fluorinated compound. Preferably, 
the fluorinated compound contains at least one fluorinated aliphatic 
radical therein. The radical can be described as a fluorinated, saturated, 
monovalent, non-aromatic, aliphatic radical of at least three carbon atoms 
in length. Examples of fluorinated compounds that will function as an 
abhesive component herein are set forth in U.S. Pat. No. 4,074,009, the 
disclosure of which is incorporated herein by reference. As set forth in 
that patent, methods for the preparation of polymers containing 
appropriate fluorinated radicals are set forth in U.S. Pat. No. 3,574,791, 
the disclosure of which is also incorporated herein by reference. A 
fluoridated compound available from Minnesota Mining and Manufacturing 
Company of St. Paul, Minnesota, under the name FC-808, has been found to 
function satisfactorily. 
Preferably, the above-mentioned solids of the pad coat are mixed with water 
to form a dispersion which can be coated onto the paper product. 
Preferably, the water and solids are mixed so that a mixture that 
comprises approximately 5 to about 60% by weight solids and approximately 
40 to about 95% by weight water is created. Most preferably, the solids 
comprise approximately 15 to about 30% by weight of the mixture and the 
water comprises approximately 70 to about 85% by weight of the mixture. 
The exact composition of the mixture will depend upon several factors. One 
of the more important determinative factors will be the type of coating 
apparatus to be utilized to coat the mixture on the paper product. 
Depending on the coating apparatus used, one may want to lower or raise 
the solid content. For example, with a Billblade coater, a mixture having 
approximately 21% by weight solids has been found to function 
satisfactorily. 
With respect to the non-water portion of the mixture, i.e., the solids, 
preferably, the solids comprise: 20 to about 80% by weight binder; 20 to 
about 80% by weight pigment; and 0.5 to about 10% by weight of the 
abhesive component. Most preferably, the solids comprise: approximately 35 
to about 65% by weight pigment; approximately 35 to about 65% by weight 
binder; and approximately 1 to about 5% by weight of abhesive component. 
If desired, the pad coat composition can include other additives. For 
example, it may be desirable to include in the composition a thickener, a 
pH adjuster, and/or a dispersing agent. 
In an embodiment, the pad coat composition includes a thickener. The 
thickener functions, at least in part, to increase the viscosity of the 
composition, which can be desirable for certain coating operations, e.g. 
when applied to unsized paper. 
Preferably, the thickener is chosen from the group of materials consisting 
of hydroxyethylcellulose, carboxymethylcellulose, or alginate. A 
carboxymethylcellulose purchased from Hercules, Inc., Wilmington, 
Delaware, under the name CMC7-L, has been found to function 
satisfactorily. 
If a thickener is used, preferably it comprises approximately 0.2 to about 
3 weight percent of the solids. Most preferably, the thickener comprises 
approximately 0.5 to about 2 percent by weight of solids. 
Whether a pH adjuster is necessary or not will depend on: the pH of the 
water which is utilized to make the mixture and the type of machinery 
being utilized to coat the pad composition onto the paper product. Certain 
coating apparatus are designed to function and coat paper with either a 
basic or acidic mixture. Accordingly, depending on the pH of the water 
utilized to make the mixture, it may be necessary to raise or lower the pH 
of the mixture. If it is desired to raise the pH of the mixture, ammonium 
hydroxide has been found to function satisfactorily. 
It may also be desirable to utilize a dispersing agent. Depending on the 
pigment that is utilized, a dispersion agent may or may not be necessary. 
If Hydral 710B is utilized, it has been found that a sodium polyacrylate 
copolymer aids dispersion of the Hydral 710B in the water. A sodium 
polyacrylate copolymer available from Colloids, Inc., Newark, New Jersey, 
as Colloids 230 has been found to function satisfactorily. If a dispersing 
agent is utilized, preferably, it comprises slightly greater than 0% to 
about 1% of the solids by weight. 
Referring now to the figures an example of a carbonless paper product 
utilizing the composition of the present invention is illustrated. FIG. 1 
illustrates a plurality of sheets of paper 10, 13, 26. As illustrated, 
sheets 10 and 13 are bonded together by an adhesive coating 20 to form a 
unit 21, which can be, for example, a form. 
Referring now to FIG. 2, the unit 21 includes two sheets of paper 10 and 
13. As illustrated, a sheet 10 is coated on a first side 12 with a front 
coating (CF) 14 and side 16 with a pad coat 18 of the present invention. 
Sheet 13 is coated on a back surface 17 with a back coating (CB) 19 
wherein the CB 19 and CF 14 cooperate to duplicate on surface 12 what is 
written or typed on surface 11. 
As previously stated, sheet 10 includes pad coat 18 . The pad coat 18 
prevents the fan-out padding adhesive 20 that is applied to an edge 25 of 
the sheets of paper 10, 13, and 26 from wetting the side 16 of the paper. 
This prevents the bottom surface 16 from being secured to a third sheet 
26. This allows the two sheets of paper 10 and 13 to be easily separated 
from the sheet 26. 
Although in the embodiment illustrated in FIGS. 1 and 2, the pad coat is 
coated on the back surface 16 of the sheet 10, the pad coat can also be 
coated on a front surface of a sheet. For example, if desired, the pad 
coat could be coated on the front surface 31 of the sheet 26. 
By way of example, and not imitation, an example of the present invention 
will now be set forth: 
In a high shear mixer, 63 gallons of water were placed. To the water, 91/4 
lbs. of Colloids 230 (0.9 gallons) were added. 1,000 lbs. of Hydral 710-B 
were then added to the water and Colloids 230. The composition was then 
mixed for 40 minutes. 
In a starch cooker, 500 gallons of water were placed. 1,100 lbs. of Penford 
Gum 260 were then added to the water. The mixture was cooked and held for 
one hour, and then diluted with water to 15% solids. 
In a blend tank, the mixture from the high shear mixer container was 
placed, and the mixture from the starch cooker was then added to the blend 
tank. To the blend tank 26 gallons of FC-808 were further added. After the 
addition of the FC-808, 201/2 lbs. of CMC7-L were added to the blend tank 
using an eductor. Two gallons of ammonium hydroxide were added to the 
mixture. The solids were then diluted to 21% of the total solution. 
The resultant pad coat had the approximate following composition; 
79% by weight water; and 
21% by weight solids. 
The solids had the following composition: 
Penford Gum: 48.1% 
Hydral: 710B 48.6% 
FC-808: 2.1% 
CMC7-L: 1.0% 
Colloids: 230 0.2% 
30,000 pounds of paper were manufactured and coated using the above 
formula. The paper was coated using a Billblade coater. 
Tested properties of the sheets of paper so coated were satisfactory. 
Padability testing revealed that the sheets of paper coated with the pad 
coat had good fanapart characteristics. Further, the pad coating had good 
printability characteristics. Print tests run on various types of 
commercial printing units showed improved ink receptivity versus other pad 
coats. 
It should be understood that various changes and modifications to the 
presently preferred embodiments described herein will be apparent to those 
skilled in the art. Such changes and modifications can be made without 
departing from the spirit and scope of the present invention and without 
diminishing its attendant advantages. It is therefore intended that such 
changes and modifications be covered by the appended claims.