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Patented Jan. 14, 1947
2,414,251
UNITED STATES PATENT OFFICE
2,414,251
METHOD OF COATING FIBROUS SURFACES
Clarence Walter Wilson, Norco, Calif., assignor to
California Fruit Growers Exchange,
Angeles, Calif., a corporation of California
Los '
No Drawing. Application February 17, 1942,
Serial No. 431,300
'
'
2 Claims. (chum-60)
1
2
.
' This invention relates. in general, to methods
of time and from many different angles, but up
of coating surfaces. More particularly the in
to the present still remained, for the most part,
vention relates to the coating of ?brous surfaces
unsolved. Although many substances or combi
with a coating which I may call a “stop coat,”
nations of substances have been suggested as pos
that is, a protective ?lm which tends to ?ll up or 5 sible coatings for ?brous materials in order to
seal the minute pores of the ?brous material. and
make them satisfactory for packaging such ma
which also tends to lay and cover the ?bers
terials as asphalt, bitumen, or such oleaginous
thereof. As examples of ?brous materials I mean
materials as bakery goods, cheeses, and confec
paper and paper-like materials, ?berboard, wood
tions, as well as greases and oils themselves, none
surfaces, ?nely woven cloth, etc.
‘
.10 has been completely successful.
This application is a continuation-in-part of
Probably the greatest dif?culty has arisen in
my co-pending application Serial No. 353,125,
the preparation and application of an impervious
?led August 17, 1940, which application relates
and continuous ?lm which will remain intact un
particularly to reducing and preventing the tend
der conditions of fabrication and use. I have
enoy of surfaces such as those of asphalt. bitu 15 found, for example, that those ?lms which have
men, highly concentrated molasses, tacky rubber,
been satisfactory‘to lay and cover the ?bers of
and the like. to stick to other surfaces, particu
a ?brous surface have often times not exhibited
larly the ?brous surfaces of materials such as
satisfactory impermeability under more trying
wood. paper, etc. The present application relates
conditions. On the other hand stop coats or ?lms
broadly to the treatment of ?brous surfaces, in 20 which have been ordinarily satisfactory for some
cluding those just mentioned, for the purpose of
uses failed to be sufficiently elastic to permit‘dis
preventing them from sticking to sticky surfaces
tortion or creasing. In addition to the require
such as asphalt, bitumen, highly concentrated
ments that a stop coat or protective ?lm must
molasses, and the like, and it includes improved
satisfactorily cover and lay the ?bers, the stop
methods for treating such ?brous surfaces for 25 coat should be ?exible or elastic enough to permit
this purpose. It ,also relates more speci?cally to
fabrication of containers therefrom’ while re
the provision of methods of treating these ?brous
maining intact, or nearly so, itself. Also the stop
surfaces with a ?lm or “stop coat” to render the
coat should notpermeate to any appreciable ex
surfaces so treated more impervious to oleaginous
tent the ?brous, material being coated,‘ since it
30 would require more material to give a satisfac
A “stop coat” is used in connection with ?brous
tory ?lm and in addition there is then a tendency
surfaces in order to reduce the tendency of such '
toward the formation of pits and holes in the ?lm.
surfaces to adhere or to stick to other surfaces,
I have now discovered methods whereby it is
particularly tacky or sticky surfaces, and, more
possible to apply a stop coat to ?brous surfaces
speci?cally, it is used to make the ?brous surfaces ' which will permit the use of these materials in
substantially impervious to the passage of ma
conjunction with adhesive substances, such as
substances.
-
‘
.
terials thereinto and therethrough. The stop
coating of ?brous surfaces is desirable when those
asphalt, bitumen, highly concentrated molasses,
materials having ?brous surfaces are used in con
nection with the handling of such sticky articles
as asphalt, bitumen, and pitch-like substances,
40
etc., and which will allow the so-treated ?brous
materials to be readily removed from the asphalt,
bitumen, etc. Furthermore I have discovered
methods by which I can coat ?brous surfaces with
as well as highly concentrated molasses and the
a protective ?lm so as to make them substantially
like.
impermeable to greases and inks. Furthermore,
and perhaps of greatest importance,’ I have dis
covered methods of coating ?brous materials, such
Also, in many instances it is desirable to
apply a stop coat to ?brous materials such as
paper and paper-like materials, as, for example,
when these are to be used to package such articles
as cheeses, bakery goods, etc., from which ole
aginous substances tend to exude and permeate
the paper. Again, ‘a stop coat ?nds application
in connection with the preparation of paper and 50
as paper and paper-like materials with a satisfaci
tory stop coat so that the so-treated ?brous ma
terials may be fabricated satisfactorily into pack
ages or containers without impairing the protec
tive ?lm.
‘
-
'
i
paper-like material prior to printing, in order to
reduce ink permeation and diffusion.
The problem of coating ?brous surfaces, such
as those mentioned above, with a protective ?lm,
satisfactorily applying said protective ?lm to the
is one which has been attacked over a long period £35
?brous surfaces to be coated. ‘The basic ingredi
- Generally stated, my invention involves the
preparation of a material to be used as a stop
coat or protective ?lm, as well as the method of
2,414,251
3
from the tops of the bubbles, making thin spots
in the ?lm which under stress tend to break, or
perhaps even break during drying, in either case
causing pinholes. Consequently the ?lm is not
substantially continuous and, therefore, permits
like.
Another object of this invention is to provide
some permeation of oils, grease, and grease-like
materials. This di?iculty is more pronounced
and disclose methods of stop coating 5. ?brous sur
face with a protective ?lm containing a pectate,
as an effective ingredient, which ?lm is resist
when coarse ?brous surfaces are treated.
I have discovered, however, that if I ?rst con
dition the ?brous surfaces before I apply the pro
ant to permeation by oleaginous materials.
A further object of this invention is to provide
tective pectate ?lm I am able to overcome the
difficulties above described, wherever they occur.
In applying the invention to the use on ?brous
surfaces such as paper, I ?nd it advantageous
to apply the stop coat to the ?nished paper.
However, as just stated, before the protective'?lm
is applied to the ?brous surface, particularly to
a porous-surfaced paper, I find it advantageous
and disclose methods of coating paper and pa
per-like materials with a protective ?lm contain
ing a pectate which ?lm is non-penetrating, non
toxic, and comparatively tough and elastic, and
which will effectively ‘?ll or seal minute pores
of the paper-like material, and will be resistant
to permeation by oleaginous materials.
to ?rst condition the surface thereof.
Other objects, uses, and advantages will ap
To con
dition the ?brous material, the surface thereof
may, for example, be completely wet with water.
This may be satisfactorily accomplished by
spraying water onto the surface of the material
being conditioned. The amount'of water neces
sary to condition the surface will, of course, de
pear more fully and at large hereinafter, and '
will become apparent from a description of the
preferred process and product embodying my in~
vention, and will present themselves to those
skilled in the art in the contemplation and use
of the invention.
4
and pinholes are a result of air being entrapped
in the voids of the ?brous surface being treated
with the pectate ?lm, and that when the ?lm
dries, these minute air bubbles or pockets ex
pand, or the drying coating draws down away
ent of my stop coat or protective ?lm is a mate
rial commonly referred to as a pectate. The pec
tate is usually made into and applied in the form
of an aqueous dispersion. Accordingly, an object
of my invention is to provide and disclose meth
ods of coating ?brous surfaces with a protective
?lm containing a pectate so as to render the
coated material useful in the packaging of such
adhesive materials as asphalt, bitumen, and the
‘
pend on the ?brousness of the surface being
treated. The more ?brous the surface, the more
As mentioned before, the materials which I
use as the basis for my stop coat or protective
?lm are those materials ‘commonly referred to
as pectates. Of this group, I prefer to operate
with the ?brous pectates, such as those described I
in U. S. Patent Re. 21,077. Ordinarily I choose to
use ?brous sodium pectate, although other ?brous
pectates may be satisfactorily used.
conditioning will be required. When relatively
more highly ?nished surfaces are being coated I
have found that relatively less water will 'be re
quired in order to completely wet and thereby
condition the surface. Presumably, continuing
with the explanation set out above, the water
eliminates, or substantially eliminates, from the
Also I may use those pectates which may be
prepared in accordance with U. S. Patent No. 40 surface voids the air that would be entrapped
there by the much more viscous pectate solution,
1,410,920.
and thus presents to the pectate solution as it is
In my co-pending application previously re
being vapplied a temporarily'smooth, relatively
ferred to, I have disclosed methods and means
air-free surface. With papers already present
whereby the tendency of surfaces such as asphalt,
ing a smooth surface substantially free from air
bitumen and the like to stick to other surfaces,
pockets by reason of having already been suffi
and particularly ?brous surfaces, is materially re
ciently sized and/or calendered, no’ additional
duced by coating the surface with a ?lm contain
conditioning will be required prior to coating.
ing pectate. The treatment of ?brous surfaces
In making use of the invention in connection
in the manner therein disclosed is satisfactory to
with paper material, I find it advantageous to
reduce the sticking tendency of asphalt and the ‘
apply the protective ?lm or stop coat to the
like to ?brous surfaces, to a point representing
paper. As previously mentioned, I may use the
commercial utility. For example, a wooden barrel
crude pectate pulp described in U. S. Patent Re.
may be treated in accordance with the methods
21,077, or the puri?ed pectate also therein de
therein disclosed, and the asphalt subsequent
ly poured thereinto will be effectively prevented " scribed.
Employing the crude pectated pulp described
from sticking to the inside of the barrel. How
in the above-mentioned patent, I make the dry
ever, I have found that such treatment as is dis
mixture containing dry pectated pulp, sodium
closed there does not produce a coated ?brous
pyrophosphate, and sodium carbonate. Since
surface which is completely satisfactory for use
with oleaginous materials in general, including (if) there may exist some variation'in the crude pec
tated pulp, due to different lots of fruit, etc., I
those which tend to continue exuding grease and
grease-like materials after packaging. I ?nd
?nd it desirable to mix the dry pectated pulp
that in some instances, and for certain surfaces,
the ?lms formed in accordance with the methods
described in my co-pending application tend to
have weak spots or “pinholes” which allow the
oleaginous exudate to permeate the treated ma
terials. The pinholes and weak spots cause very
little trouble when packaging materials such as
withv an amount of NarPzO-z falling within the
range of ‘from about 5.0% to 10.0% based on
” the weight of the pectated pulp. The sodium
carbonate is added in an amount su?icient to
give a pH in the ?nal pectate dispersion of above
asphalt, bitumen and the like, which materials 70
7.5. Ordinarily this amount will be approxi
mately 5% of the weight of the pectated pulp
in the dry mixture.
'
v
tend to harden on cooling, with diminishing
‘To an appropriate quantity of hot, and pref
oleaginous exudation. With greases, oils, etc.,
however, the tendency toward permeation of the
package material is ever present.
In theorizing, Lbelieve that these weak spots
erably boiling, water I add sufficient of the pec
tated pulp mixture to give the desired concen
tration of pectate in the dispersion. I prefer
to boil the dispersion mixture with rapid agi
,
5
tation for about 5 minutes in‘ order to insure
substantially complete dispersion of the pulp.
The dispersion is then ready for use but it may
preferably be somewhat cooled before applica
tion. It may be applied to the conditioned sur
face in any desired manner, as by spraying, dip
ping, brushing, or rolling. In applying the pee
tate dispersion to the surface of the paper, I
have found that a dispersion containing about
2.0%‘of the pectated pulp by weight goes on
very readily and gives a uniform, coated surface
designed to give a protective ?lm. On the other
hand, a dispersion of 6.0% by weight of pectate
produces a coating of a thickness very satisfac
tory under some circumstances.
paper where it is desired to use the paper in con
nection with the packaging of substances or ma
terials tending to adhere thereto, or those ma
terials which tend to exude oleaginous materials.
If the paper is to ‘be subsequently creased or se
verly distorted, I ?nd it desirable to add a plas
ticizer to the dispersion prior to the application
of the dispersion to the paper.
»
As examplesof suitable plasticizers, I may use
glycerol or‘sorbitol. A mixture of glycerol and
urea is also satisfactory as a plasticizer.
The
plasticizer is preferably added to the dispersion,
although it may be sprayed over the pectate ?lm
after application. The glycerol maybe used in
15 an amount of about 60%, based on the weight of
After the ?lm is applied, the paper is then
dried. It may be formed into containers, as
desired. Such paper coated in accordance with
the above disclosure may be constituted into con
tainers to receive such adhesive materials as 20
pectated pulp in the dispersion. When a mixture
of glycerol and urea is used, I have found it satis
factory to add the glycerol to the dispersion in an
amount equal to about 30% of the weight of the
pectated pulp in the dispersion. The urea is
asphalt, bitumen, and the like.
added in an amount equal to about 80% based on
As a further example of the methods and
the weight of the pectated pulp in the dispersion.
means of stop coating ?brous surfaces, I may
When applying the dispersion to the surface of
proceed in accordance with the following ex
paper or like material, I have found that a satis
ample:
25 factory coating will be obtained if the dispersion
Using a kraft paper as an example of the ?
is applied in amounts not less than 1A pound of
pectate per 1000 square feet of paper. Larger
brous material to be coated, I ?nd it advan
tageous to apply the stop coat to the ?nished
amounts of pectate may be used if necessary.
paper after the paper has been conditioned. I
Also, if desired, more than one coat may be ap
have found that about 100 ounces of water will 30 plied to the paper, although adequate time should
satisfactorily condition 1000 square feet of paper.
be allowed between applications for the drying
of the previous coat.
After the paper has been conditioned, and before
any appreciable drying has taken place, the pee
If desired, both sides of the ?brous material
tate dispersion is applied to the surface in any
being treated may be coated with one or more
convenient manner. as by spraying. Suitable 35 coats.
application may also be made by brushing or
After drying the coated material may be
by a doctor blade.
formed into containers if desired. It is also to be
vIn preparing the pectate dispersion a quantity
noted that the stop coat or protective ?lm may
of pectated pulp is mixed with the sodium car
be applied to preformed containers. These appli
bonate and sodium pyrophosphate in accordance
cations may easily be madeby spraying pectated
with the previous disclosure. I have found,
pulp dispersions over the surface of the con
however, that ordinarily the following propor
tainer.
tions by weight may be conveniently used.
For some purposes I ?nd it desirable to add
to the pectate dispersion an adhesive such as ordi
Parts
nary glue, or other suitable adhesive, which mani
Crude pectated pulp____________________ __ 20.0
festly should be water-soluble. The adhesive
Sodium carbonate
_ 1.5
seems particularly desirable if the coated ?brous
Sodium pyrophosphate __________________ -_
1.0
material is to be subsequently printed, for, in
Using the above dry mixture as the base for the
certain types of printing and similar operations
preparation of the aqueous dispersion, one part '
the surface of the paper, perhaps in its entirety,
of the dry pectated pulp mixture is added to 20
, or perhaps‘ in more or less isolated spots, may be
parts of boiling water with stirring. The stirring
subjected to considerable pull, and any tendency
should be of the type which preferably keeps the
which any such operation might have to loosen
resulting dispersion as free from air as possible,
the surface coating should be carefully guarded
and should be continued until the pectated pulp
against
‘
is completely disintegrated. If considerable
About 30% glue based on the weight of the
quantities of air are beaten into the dispersion by
crude pectated pulp in the dispersion seems to
the agitation, it may be desirable to deaerate the
improve thestop coat. Larger amounts of glue
dispersion, depending upon the method of ap
may be desirable under some circumstances.
plieation of the dispersion. After substantially
If purified ?brous pectates referred to in Re
complete dispersion of the pulp has been ob
issue Patent No. 21,077 are used, it should be
tained, the dispersion may be screened to remove
pointed out that it will not be necessary to use
any large, undispersed particles. I have found it
the alkaline ingredients such as sodium carbo
desirable to pass the dispersion through a screen
nate and sodium pyrophosphate as dispersion
of about 100 mesh in order to remove any remain
aids. It should be kept in mind that a lesser
ing coarse particles of pectated pulp and any un
quantity of puri?ed pectate will be required.
dispersed pectated pulp. If, however, the pec
Since the crude pectated pulp usually contains
tated pulp is finely ground, and the dispersion
about 30% pectate ordinarily, only about one
complete, this step of screening may not be nec
third as much of the puri?ed pectate will be re
essary. Other satisfactory means of removing
quired for an equivalent dispersion, as when. using
the coarse particles of pectated pulp, or any in»
the crude pulp. In other respects the formula
dispersed pectated pulp, may be used, as for ex
given for the crude pectated pulp‘is satisfactory
ample centrifuging.
when using the puri?ed ?brous pectate.
The above dispersion, on cooling or while warm,
as previously described, may be used to coat the
Having thus described my invention in such
clear, concise, and exact terms as to enable others
2,414,251
v7
skilled in the art to make and use the same, I
claim as my invention and desire to secure by
Letters Patent the following:
1. A method of treating paper which is nor~
mally pervious to oleaginous materials to render
the same substantially impervious to such mate
rials comprising, conditioning the surface of said
paper by wetting the same with water and before
any appreciable drying has taken place forming
on the conditioned paper a substantially con
tinuous ?lm containing a ?brous pectate in an
amount not less than 1/2 poundoi .pectate per
thousand square feet of surface.
I
2. A method of treating material having a li
brous surface comprising, conditioning said ma-.
terial by Wetting the surface thereof with water
and before any appreciable drying has taken
place forming on the conditioned surface a sub
stantially continuous ?lm containing a ?brous
pectate in an amount not less than 1/2 pound of V
10 pectate per thousand square feet of surface.
CLARENCE WALTER WILSONK
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