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Патент USA US2108808

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Patented Feb. 22, 1938
Theron G. Final and Donald E. Drew, Kenmore,
N. Y., assignors, by mesne assignments, to E. I.
du Pont de Nemours & Company, Wilmington,
Del., a corporation oi’ Delaware
vNo Drawing. Application June 26, 1934,
Serial No. 732,442
17 Claims.
This invention relates to transparent paper, vention, there'is incorporated in the paper, prior‘
which is preferably also moistureprooi, and also to the calendering operation, a wetting agent,
such as soap, as explained fully in copending
to a method of producing the same.
application Serial No. 732,440, ?led June 26, 1934.
Since, the advent of widespread use of moisture
The transparentizing impregnant should com 5 .
proof transparent regenerated ' cellulose sheet
ing for wrapping foodstuffs, cigarettes, cigars, etc. ' pletely ?ll the voids,- spaces, etc. in the paper and
?bers thereof. This can be accomplished by any
for the purpose of protecting these variousprod
convenient procedure. The paper may, for ‘ex
ucts from dust, air and moisture, while still per
mitting complete visibility thereof, many attempts ample, be passed through an aqueous solution
containing the impregnant; and the excess solu- 10
10 have been made to produces. transparent ‘and
preferably also moistureproof paper. Most of the tion removed in any well-known manner, suchv
as allowing the excess solution to drain oh the
investigations have been directed to the produc
tion of an improved glassine paper. However; paper or removing the excess by squeeze rolls,
even the improved glassine papers do not possess doctor knives, metering rolls, etc. The desired
amount oi’ solution containing the impregnant 15
the glass-clear transparency of regenerated cellu
lose sheeting. A certain haziness, apparent on may also be applied by means of transfer rolls,
buffers, brushes, etc.- The impregnation with the
' _ wrapped articles, as the dulling of bright colors,
'always exists in the glassine-type paper. Another transparentizing medium may be facilitated by
detrimental and undesirable property of glassine subjecting the paper to vacuurnlbefore, during
or after the application of the impregnating solu- .20
20 paper is its inherent brittleness, that is, its tend
- ency to rupture at sharp folds or at the comers I
of packages This is apparent in the ?lm as white
spots or lines.
We have found that we can produce a trans
25 parent paper by impregnating a highly calendered
tion; by subjecting the papento pressure while it
is in contact with the impregnating solution; by
the proper maintenance or temperature; or by
any suitable combinations of these conditions.
The impregnating material contemplated by 25
tissue paper, preferably also containing a wetting the instant invention is of such a nature that it
agent, with an impregnant, hereinafter more fully ' gives the desired extreme ?exibility and tough
explained, which completely ?lls all the air spaces ness. The transparentizing impregnants gener
and voids in the paper. When a moistureproof ally are themselves closely related to cellulose in
optical properties. Thus, the thoroughly im- 30
pregnated paper amounts to a continuous cellu
lose ?lm. Due to the nature of the impregnants
It is, therefore, an object of this invention to and the mode of application thereof, bonding between the celluloseof- the paper and the impreg
provide a transparent and preferably also mois
_nant is exceedingly strong and softening is 35
35 tureproof paper.
Another object of this invention is to provide mutual.
It is desirable that the solutions oi the trans
a method of producing a transparent and prefer
30 product is desired, the transparentized paper is
coated or impregnated with a moistureproo?ng
ably also moistureproof paper.
Other objects will become apparentfrom the
40 following description and appended claims.
The instant invention contemplates impreg
nating paper with a substantially transparent
water-soluble material having an index of refrac
tion substantially the same asthat of the cellu
45 lose ?bers. When a moisturepro'of product is
desired, the impregnated material, after the im
pregnant has been ?xed in any convenient man
ner, is thereafter coated with a selected moist-ure
proof- composition. The ?nal product is highly
50 transparent, clear, ?exible, non-tacky, and pos
sesses good surface slip. It is admirably ‘suited
for use as a wrapping tissue.
In the preferred embodiment of the invention,
the paper, prior to impregnation, is super-calf
endered. Also, in the preferred form of the in-'
parentizing impregnantsube moderately ?uid in
concentrations of about 15%. It, is, however, to
be understood that it is not to be implied that 40
the instant process cannot be worked with vis
cous solutions, since some materials which are so
viscousas to be almost pasty will impregnate
paper quite, thoroughly though slowly. There,
however, appears to be a relationship between 45
viscosity and a tendency for the impregnant to
shrink during drying. Generally, the higher the
viscosity at one concentration, the greater the
tendency for shrinkage. This excessive shrink
age has an undesirable e?ect because the solids Q
of the solution tend to pull away from the paper
?bers during drying, leaving the ?lm in a spotty
or hazy condition. Moreover, the shrinkage is
sometimes strong enough to actually break the
water-weakened paper.
; 55
In so far as the instant invention is concerned,
beater, on the wire, at the presses, or at any
propriate liquid vehicle, such as water, water and
other convenient operation. In the preferred
embodiment of this invention, the transparent
izing impregnant is applied in an operation sub
sequent to the manufacture of paper, that is, to
alcohol, water and acetone, etc. For example,
when an impregnant consists of a plurality of
solid ingredients, one component thereof, when
used alone, may give highly viscous solution and
the paper base is of the thin, porous type and
has the following characteristics:
it is to be understood that the impregnating
composition may consist of a single compound
or a plurality of ingredients dissolved in an ap
10 be of no value for transparency, but when moth
a ?nished paper.
In the preferredembodlment of the invention,
. Free from opaque filling material.
?ed by the other components may give a compo
. Substantially free from water-resisting sizes.
sition which gives the desired effect. The pre
. Has inherently transparent ?bers.
ferred impregnating materials are those which
. Has a relatively smooth surface, such as may
are soluble in water to give practically clear so
be obtained by super-calendering.
lutions and which, when dry. give clear ?lms.
. Is relatively compact, that is, of high solid
But, as will be explained?hereafter, it is not es
sential that this be so. The preferred impreg
. Of low basis weight, not over about 20
nants are also those which, when applied to paper
pounds, 24" x _36", 500 sheet ream.
and ?xed thereon, leave the paperin a sum
cientiy non-tacky state, so that the impregnated Though the process is most readily applied to a 20
film will not stick to itself when wound up. porous paper, such as super-calendered tissue, it
When the transparent paper is to be given a sub-‘ can also be used on ‘non-porous paper, such as
sequent coating, such as when the product is to thin glasslne paper, since by the process the
be rendered moistureproof, non-tackiness is of no non-porous papers are expanded by the aqueous
impregnating solution to such an extent that im
material importance.
As illustrative examples of the impregnating pregnatlon may. be absolutely complete. As
transparentizing materials contemplated by the above explained, for .the best and most rapidly
obtained transparency, a.v wetting agent, such as
instant invention may be mentioned the water
whlte variety of water-soluble or partly water . soap, is incorporated in the paper prior to im 30
soluble substances, such as starch in various pregnating, andvpreferably also prior to super
stages of deaggregation; thin boiling sizing
starches, dextrin; oxidized staches: brewer's
body syrups; chlorine-treated starches and other
starches hydrolyzed by various means; starch
35 esters and ethers, such as starch acetate‘ to vary
ing degrees of acetylation up to insolubility in
alcohol-water or acetone-water mixed solvents;
In the foregoing embodiment of the inven
tion, aqueous solutions of the impregnants are
contemplated. As an alternative procedure, the
instant invention also contemplates passing the 35
paper through a bath of transparentizlng im
pregnants kept in the ?uid state by heat. After
wholly water-soluble gums, including sugar alde ‘passage throughthe molten impregnant and the
hyde, urea-formaldehyde and hydrolyzed vinyl removal of the excess material from the impreg
40 acetate resins; or sugars, such as cane sugar or riated paper by any suitable means, the impreg
hydrogenated sugars; sorbitol; various types of nant is solidi?ed in any convenient manner, such
degraded or hydrolyzed celluloses, such as hemi- ' as chilling.
cellulose or cellulose precipitated from concen
trated sulphuric acid solutions or derivatives of
various oelluloses which are soluble‘ in water or
water-alcohoLsuch as methyl cellulose, glycol cel
lulose or acetates of degraded cellulose. These
materials may be used alone or in combination
with each other or in combination with other sub
stances, for example, substances which soften
either or both the cellulose and transparentizing
impregnants. As illustrative examples of such
softeners may be mentioned glucose, glycerol.
glycol or_derivatives thereof; soluble oils, such
It is; of course, understood that‘
this procedure is not limited to any precise man
ner of application, since any procedure and
means. will sufjilce as long as there is applied to
the paper a. uniform and controllable amount of
the molten impregnant. In some cases it is not
even necessary to maintain the impregnant in
a liquid state until impregnation is complete.
Impregnation may proceed even after chilling.
This alternative procedure of using molten im
pregnants possesses the advantage that inex
pensive and less complicated equipment can be
used. Also, an impregnant that gives the paper
a relatively tacky surface can be used without. 55
and their salts or
These softeners in very great trouble, since the impregnated paper
many cases serve for purposes other than merely may be surfaced, without the tacky paper ever
?exlbllizing films, for example, they may pre
coming into contact with any supporting mecha
vent spottiness ‘of the ?lm; they may increase nism, with a non-tacky coating.
speed and thoroughness of impregnation; they
As illustrative examples of substances which
may increase the transparency of the dry im
can be used in the molten condition may be men
pregnated base. either by elimination of a nat
tioned glucose, sugar, sorbltol, sugar aldehyde
ural haziness of one of the components of the resin, acetone formaldehyde resin, or any other
impregnants or by changing the index of refrac
material having similar melting and solvent
, tion of the composition to more nearly that of properties. It is desirable that the materials 65
the cellulose fibers. '
melt at a temperature below the charring point
The quantity of transparentizing impregnant thereof and be relatively ?uid at temperatures
incorporated in the paper may vary within wide below'the point where the paper is harmed or
limits, depending upon the characteristics of the appreciably embrittled. This temperature for
70 ultimate product. Satisfactory results have been the most part is below 120° C. When the above 70
secured when the impreg'nant constitutes ap
proximately 10% to 30%, by weight, of the paper. mentioned materials melt at too high tempera
tures or melt to form liquids too viscous for
The tran'sparentizing impregnant may be in
corporated in the paper at practically any stage good impregnation, a small quantity of water may
be added thereto. The amormt of water added 75
75 of the paper-making operation, such as in, the
55 as sulphonated castor oil and hydroxy fatty acids
is preferably limited to such an amount that the
swelling of the paper is slight. Also, the quantity
of added water is suchthat it can be evaporated
while the ?lm is yet unsupported and still pro
duce anon-wrinkled and non-‘distorted ?lm. To
accomplish the removal of this small amount of
added water, which is preferably reduced only
to an extent at which it is in. equilibrium in the
impregnated paper with room conditions of tem
10 perature and humidity, there is provided a short
drying chamber maintained at an elevated tem
perature through vwhich the ?lm is passed after
being maintained at such a value as to give a
humidity differential of at least 95%.
Moistureproo?ng coating compositions are de
?ned as those which, when laid down in the form
of a thin, continuous, unbroken ?lm applied uni
formly as a coating with a total coating thick
ness not exceeding 0.0005" to both sides of a sheet
of regenerated cellulose of thickness approxi 10
mately 0.0009", will produce a coated product
which is moistureproof.
leaving the impregnating bath and the surplus
removing devices.
For the purposes 'of experimental tests, espe
cially for those materials adaptable as coating
In this alternative procedure, paper of the
more porous type, such as super-calendered tis
sue, is preferred, because these papers are sub
‘those substances, compounds or compositions
je‘ct to the most complete impregnation in the
shortest time.
being maintained at least at 98% and the rela
tive humidity of the atmosphere at the other side
The transparentizing impregnants hereinbe
compositions, moistureproof materials include 15
which, when laid down in the form of a continu
ous, unbroken ?lm applied uniformly as a coat
ing with a total coating thickness not exceed
ing 0.0005" to both sides of a sheet of regener 20'
fore mentioned have many advantages. Once the
ated cellulose of thickness approximately 0.0009",
paper has been transparentized therewith, it may
be moistureproofed by practically any known
will produce a coated sheet which will permit the
passage therethrough of not more than 690 grams
process without any detrimental elfects or se
25 rious complications. The water-soluble impreg
nants are of such a nature that’ they are not
of water vapor per 100 square meters per hour
over a period of approximately 24' hours, at a 25
temperature of 395° C.:0.5° C. (preferably 39.5‘?
substantially disturbedv or altered by practically
C.-i_-0.25° C.), with a water vapor pressure differ
any known method 01' moistureproo?ng - Thus,
ential of 50-55 mm. (preferably 53.4103! mm.)
of mercury. For convenience, the number of
grams of water vapor passed under these condi-. 30
tions may be referred to as “the permeability
value". An uncoated sheet of regenerated cellu-_ ‘
lose having a thickness of approximately 0.0009"
the instant process, in contradistinction to other
30 processes, does not limit the composition and
methods which may be used for the application
of a subsequent coating.
When the transparent paper hereinbefore de
scribed is to be moistureproofed, any suitable
grgiéloshow a permeability value of the order of
35 moistureproo?ng composition may be applied
As illustrative moistureproo?ng com
positions'may be mentioned those which con
sist of the following ingredients in such propor
tlons as to give thin, transparent, moistureproof,
non-tacky coatings:
1. Cellulose derivative, wax, and solvent:
2. Cellulose derivative, wax, plasticizer, and
3. Cellulose derivative, wax, gum, and solvent;
4. Cellulose derivative, wax, gum, plasticizer,
and solvent;
5. Resin, wax, and solvent;
6. Resin, wax, plasticizer, and solvent;
7. Wax compositions.
. Though the invention has been described in
connection with the production of transparent
paper, that is, plain glass-like ?lms, the proc
ess may be modi?ed to obtain various results,
55 such as colored products. Colored ?lms may be
produced by dyeing the paper, by dissolving a
dye in the impregnating solution or in the mois
tureproo?ng composition, or a coloring sub
stance may be applied at any convenient stage
'60 in the preparation of. the transparent paper.
The paper may be dyed one color and the im
pregnants dyed another color, whereby mottled
effects are secured.
The paper may be em
bossed or designs pressed 'thereinto. ‘ Addi
65 tional crystallizing materials may be incor
porated in the impregnant toyield frosted de
ljor the purposes of this speci?cation and
claims, we, define moistureproof materials as
70 those which, in the form of continuous, unbroken
sheets or ?lms, permit the passage of not more
than 690 ‘grams of water vapor per 100 square
5 meters per hour, over a period of 24 hours, at
approximately 39.5" C.¢0.5° C., the" relative hu-
75 midity of the atmosphere at one side of the ?lm
From the foregoing, it is apparent that under
the conditions set forth, a moistureproofed re
generated cellulose sheet is capable of resisting
the passage of moisture or water vapor there
through at least ten times as effectively as the 40
uncoated regenerated cellulose sheet.
In order to more fully explain the nature of
the instant invention, the following illustrative
examples are set forth:
Example I
(A) _A‘ thin porous sulphite tissue between 13
pounds and 18 pounds basis weight (24 x 36-500)‘
v. is treated 'with'the following solution consisting
of the ingredients in approximately the propor 50
tions set forth:
- I
Per cent by weight
Ammonium oleate ______________________ __
____ __
Denatured alcohol ______________________ __ 77.1
The excess soap solution is'removed by means
of squeeze rolls and the wet tissue is passed over 60
dryer rolls. The drying is continued until the
tissue feels distinctly moist (10% to 15% mois
ture). The damp tissue is passed through a
supercalender stack, the rolls of which are cooled.
This is followed by a second super-calendaring
operation in which heated rolls are used. If de
sired, these calendaring operations may be com
bined, as by, using a stack in which one-half the
rolls are cooled, the other heated. As the tissue 70
emerges from the hot calender rolls, it is dry
and has a ?ne ?nish. While its solid fraction
has been consideriatblyv increased, the calendered
paper still retains a good proportion of its ab
Q, 1 08,808
drying operation, the coated paper is conducted
The super-calendered tissue is then treated
through a humidifying chamber maintained at
40° C. to 70° C. and 60% to 95% relative humid
with- a transparentizing composition consisting
ity to restore the film to its normal moisture con
Per cent by weight
tent, and the ?lm wound up.
Starch acetate ___________________________ __ 20
The starch acetate is prepared by re?uxing
corn starch with equal parts of glacial acetic
acid and acetic anhydride for 1 hour. The starch,
acetylated to about 12% acetyl content, is ill
tered, washed free of acid with methanol, and
dried. The dried product is used in- the above
composition. Small amounts of acid catalysts,
following composition:
Per centbyweight 15
30 held at 20° C. to 70° C.‘ The excess is immedi
ately removed by passing the paper between
squeeze mils or through scraper ‘rods.
.cient solution is left on the paper so that when
Re?ned carnauba wax ____________________ __ 47
Rubber (crepe) __________________________ __ 8
100 20
The paper is passed through the molten com
position and then through a set of two doctor
knives on each side of the film by which all but
a uniform layer of composition is scraped from 25
the film. About 5 pounds of the wax composition ‘
to 100 pounds of the transparent film are applied.
The product obtained is moistureproof, trans
parent, glossy, free from white haze, non-smeary, 30
and su?iciently tough and ?exible to withstand
drastic ?exing and creasing without showing un
desirable white lines.
the water is evaporated about 20 ‘pounds to 30
Example 11
35 pounds of impregnant to 100 pounds of paper
remain. After removing the excess solution, the
paper is carried over cold rolls for a su?'icient
period of time to allow thorough impregnation.
This time is usually about 5 seconds to 10 sec
40 onds.
The paperis then passed over hot rolls
to evaporate the water, and the dried film is
(A) The same calendered paper as in Example
1(A) is impregnated and dried exactly as in that '
example, but using the following impregnating
Per cent by weight
Starch acetate
White parafnn wax _____________________ _;- 47
such as sulphonic acids, may be added in the
starch acetate preparation to facilitate acetyla
20 tion and to reduce the viscosity of the product.
In preparing the above composition, the starch
acetate is ?rst dissolved by making a smooth
paste of the starch acetate with equal parts of
water, then adding the remainder of the water
25 and glycerol and heating the whole solution near
ly to boiling. The solution prepared will be
slightly viscous and very slightly milky.
The impregnating solution is applied to the
paper by immersing the paper into the solution
wound up.
from spots or white haze. Furthermore, its ?ex
ibility and toughness is such that it can be
creased and foldedywithout the appearance of 10
white lines.
(C) The transparent, ?exible film obtained in
Example HA) is passed through a melt of the
The ‘product obtained is moistureprooi, trans
parent, non-smeary', non-tacky, glossy and free
The paper thus produced is transparent, free
Sorbitol _________________________________ __ 10.
from any white haze or spottiness, glossy, non
_- '10
45 tacky, and. when in equilibrium with room hu
midity, of exceptional ?exibility and toughness.
(B) The transparent ?exible product of Ex
ample HA) is coated with a moistureproo?ng
lacquer consisting of the following compomtion:
Per cent by weight ,
'Ihe ?lm obtained is glossy, non-tacky, free
from white spots or haze, and of exceptional
?exibility. Its transparency is somewhat better
than that oi-Example I(A) , since the refractive
index of the impreanant is more nearly that of
the cellulose.
Gum dammar
___ 34
(B) A moistureproof, transparent, and flexible
'I‘ri‘cres'yl phosphate ............... -‘__...'--__ i2. film is produced from the product of Example
IHA) by coating it with the following composi
Paraiiin wax-100 tion and by the procedure outlined in lix-v
Per cent by weight ample 1(3) :
Per cent by weight
Ethyl acetate ____________________________ __ s2
Nitrocellulose ...... -. ____________________ ___
Alcohol __- ______________ _'. ________ __'.._____
Buty'l acetate_..
\Solids content
. 10°
‘The transparent film is passed through the
above lacquer, held at 85‘ C. to 45° C. and then
passed through knives which remove all but a
70 thin uniform layer of lacquer. The ?lmis then
passed into a chamber held at 60° C. to 100° C.
for such a time as is necessary to evaporate the
lacquer solvents. 1!. any considerable amount of
moisture is lost from the base him during the
Pyroxylin _____________________________ __
Gum dammar ________________________ _-__
Dibutyl phthalate _____________________ __
Paraflln (62° C. M. P.) _____________ ___-..”
Zinc steam?»
_ 35.63
Ethyl acetate _________________________ __ 45.76
Ethyl alcohol _____ _. ___________________ __‘ 6.22
Acetone___________________________ ___7____
A product is obtained which is equal to that a '
Example H3) in strength and ?exibility and is
superior in transparency and clarity.
v(C) The same calendered paper as in Example
I(A) is treated with the following impregnating
obtained, while being transparent and ?exible,
‘Per cent by weight
Starch acetate (high acetyl content) ______ ..- 20
Water ___________________________________ -_ 30
Denatured alcohol--. ____________________ .... 40
The paper is passed through the impregnating
solution and then through squeeze rolls to remove
the excess solution. When impregnation is com
15 plete, the paper is passed over hot dryer rolls and
the paper dried.
There are some advantages in using the higher
starch acetate. The above solution is usually
somewhat less viscous than previous starch ace
20 tate solutions and, therefore, it more v rapidly
penetrates or impregnates the paper; the starch
acetate of higher acetyl content usually results
in a more transparent ?lm; the use of alcohol in
the impregnating solution decreases the softening
25 power which water has on the thin tissue, so that
there is less likelihood of breakage in the im
pregnating solution.
The product obtained is very transparent and
glossy and of excellent ?exibility. It may be
30 moistureproofed with any convenient composi
tion and means.
Example III
(A) The same paper as in Example HA) is
the same treatment as in Example 1(A) , ex
cept that the following impregnating solution is
Per cent-by weight
Sizing starch __________________________ __-_r 20
40 Glucose________________________ ___‘_--_....__ 20
Somewhat highly oxidized starch, such as a
thin British gum, may be used. The product‘
is too tacky to betwound up on itself. Conse
quently, it is desirable. to apply immediately any
suitable moistureproo?ng composition by which
atransparent and ?exible ?lm is obtained and
through which tackiness is eliminated.
Example IV
(A) A tissue between 13 pounds and 18 pounds
basis weight (24 x 36-500) is passed through a
calender, preferably in a slightly moistened con
The calendered paper is impregnated with a
50% sorbitol solution in water by supplying
about 10 pounds of solution to. 100 pounds of
paper to each side of the ?lm with suitable
hoppers. The paper ispassed over cold rolls 20
until impregnation is complete, and-then over
hot rolls to expel the water. Without winding
the ?lm up, it is immediately coated with a
moistureproofing lacquer following the procedure
in Example 103). The product obtained will be 25
moistureproof, free from "haze or spots, trans
parent and very ?exible.
(B) A good grade of glassine, 20 pounds basis
weight, is passed through a 50% sorbitol water
solution and then through squeeze rolls to re 30
move all but about 15 pounds to 30 pounds of
solution, to 100 pounds of glassine. The paper
is rolled up and allowed to stand for l to 5
hours. During the time of standing, a limited
amount of swelling proceeds (the full swelling 35
power of the water is limited by. the high con
centration of sorbitol) and the sorbitol slowly
penetrates into the film. displacing the entrapped
air.v When the glassine has been su?‘lciently
impregnated, it is dried on dryer rolls or other
suitable means, and the tacky transparent film
passed through a moistureproo?ng lacquer as‘
The sizing starch used here is a hydrolyzed
45 corn starch commercially produced by the Corn
“Products Re?ning Company ‘and sold as Amidex
The product obtained, while being exception
ally tough and ?exible, has a somewhat hazy and
50 dull appearance, is of rather poor transparency,
and is somewhat tacky. Instead of winding up
the ?lm in this condition after drying, it is
passed ‘directly into a moistureproo?ng lacquer
and coated as in Example 103).
outlined in‘ Example 1(3).
The product obtained will be very transparent,
exceptionally ?exible and tough, glossy, non
smeary and moistureproof, and will be free from 45
the normal glassine haze and spottiness.
the sorbitol treatment been omitted and the
glassine simply coated with a moistureproo?ng
lacquer, both transparency and ?exibility. would
have been markedly less and the original hazy,
spotty appearance of the glassine notmaterially
(C) The same calendered' sulphite tissue as in
Example RA) is treated with a water-soluble 55
The moistureproof product obtained will
possess its original ?exibility and toughness and
in” addition will have imparted to it by the coat
resin solution of the followingcomposition:
ing procedurea good degree of transparency and
gloss, and will be free from any haziness or
Per cent by weight
(B) A transparent, ?exible ?lm, similar to
that obtained in Example II(A), except for a
slightly greater degree of vtackiness, is obtained
65 if the calendered sulphite tissue, instead of being
impregnated with a starch acetate solution, is
impregnated with a solution of the following
Per cent by weight
Oxidized starch _______________ _.-...__‘____ __ 20.0
Sorbitol ___ -
_The _resin used in this example is the con
densation product of acetone and formaldehyde, 65
a slightly yellow, slightly brittle resin. The resin
solution is applied, the water evaporated, and
the product coated with a lacquer as in Example
IV(A). A glossy, non-smeary, moistureprooi'
product of high transparency and great ?exibil
ity is obtained.
1Emample V
Water ______________________ __'..-_‘;_‘__'_~_'_; 70.0
(A) The same calendered tissue as in Example
I(A)- is impregnated as follows: The paper is
WM through a tank containing sorbitol'which
B, 108,808
and thinly coated with a transparent moisture
has been heated sumciently to be a slightly vis
'cous liquid, then out of the tank and through ‘proo?ng composition, said impregnant being
doctor knives so adjusted as to remove all ‘but present in an amount of 10% to 30%, by weight,
about 10 pounds of sorbitol for 100 pounds paper. T of the paper.
2. ‘"A transparent moistureprooi material com
It is preferable that the surface of the paper be
prising highly calendered porous paper contain
completely covered with a thin -?lm of the sor
bitol. The sorbitol is kept in a molten condition ing a ‘wetting agent and having its voids and
until the paper is thoroughly impregnated and spaces substantially completely ?lled with a
is then cooled by a blast of cold air or is simply water-soluble impregnant and thinly coated with
allowed to cool oi.’ itself. The impregnated paper a transparent moistureprocilng composition, said .
is passed between suitable hopper lips or over impregnant being present in an amount of 10%
transfer rolls by which a molten wax composi
tion similar to that of Example 1(D) is uniformly
applied to both sorbitol sur!aces.__ ‘If the original
sorbitol bath contains the proper amount 01'
moisture, it is not necessary to further humidity
the ?lm.
The product obtained is very glossy and trans
parent, moistureprooi, non-tacky and non
20 smeary, and of exceptional ?exibility.
(B) The same paper is given the same treat
ment as in Example IV(A) , except that a molten
bath of the following composition is substituted
for the sorbitol:
Percent by weight
to 30%, by weight, of the paper.
' 3. A method of making a transparent material
which comprises incorporating a non-volatile
wetting agent in paper, highly calendaring the
paper, impregnating said paper to substantially
completely fill the spaces and voids thereinwith
a water-soluble transparentizing agent whereby
the paper is transparentized, and ?nally apply
ing a transparent, moistureproof coating to the 20
transparentized paper.
4. A method of making a transparent material
which comprises incorporating a non-volatile
wetting agent in paper, highly calendering the
paper, impregnating said paper to substantially
completely ?ll the spaces and voids therein with
an aqueous solution containing a water-soluble
Corn syrup-_..;___. ___________________ .._..l 30
transparentizing agent, evaporating the water
whereby the paper is transparentized, and ?nally
applyingvla transparent, moistureprooi' coating
Glucose ________________________________ __
‘ 100
‘N a
to said transparentized paper.
5. A method of preparing transparent material
before chilling the molten composition, since im- ' which comprises incorporating a non-volatile
pregnation with this composition proceeds slowly, wetting agent in paper, highly calendering the
even at room temperature. The product will be paper, impregnating said paper to substantially
similar in all respects to that of Example V(A) . completely ?ll the spaces and voids therein with
(C) The same paper as in Example I(A) is a water-soluble transparentizing agent in the
molten state, setting the impregnant whereby
impregnated with:
the paper is transparentized, and ?nally apply
Percent by weight ing a transparent, moistureproof coating to the 40
Dextrin ___
transparentized base.
a ____ ..
6. A method of making a transparent material
Water ______________________ -_’.. ________ __
which comprises incorporating a non-volatile
wetting agent in paper, highly calendering the
100 paper, impregnating said paper to substantially
The paper is passed through this solution held completely ?ll the spaces and voids therein with
at a su?lciently high temperature to be ?uid, a water-soluble substance selected from the class
thence out of the solution and through suitable which consists of starches and starch compounds;
and hydrolyzed vinyl resins; whereby the paper
doctor knives or squeeze rolls to remove the ex
.cess. Aiter removal of the excess solution, the is transparentized, and applying a transparent 50
?lm is'passed through a shortv drying chamber moistureprooilng coating.
7. A transparent material comprising highly
held at an elevated temperature, by which the
water is evaporated to such a content as to bein calendered paper containing a wetting agent and
having its voids and spaces substantially com
equilibrium with room humidity. The impreg
pletely ?lled with a water-soluble substance se
55 nated paper is then passed through a moisture
lected from the class which consists of starch
proo?ng lacquer and coated by the same pro
and starch compounds, said substance being pres
cedure as outli ed in Example 1(B) .
ent in an amount of 10% to 30% by weight of the
The prod t obtained is non-tacky, non
smeary, glossy and of ‘very good transparency paper, said paper being thinly coated with a trans
With this composition it is not necessary to al
low impregnation to proceed fully to completion
and ?exibility.
We claim:
parent moistureprooi composition.
‘ '
Though the invention has been particularly de
scribed in connection with transparent and mois
tureproof paper, the principles thereof are equal
ly applicable to non-moistureprooi', such as, for
example, waterproof, and transparent paper.
Since it is obvious that various changes and
modi?cations may be made in the above descrip
tion without departing from the nature or spirit
thereof, this invention is not restricted thereto
70 except as set forth in the appended claims.
l. A transparent moistureprooi' material com
prising paper containing a wetting agent and
having its voids and spaces substantially com
78 pletely ?lled with a water-soluble impregnant
8. A‘ transparent moistureproo?ng material
comprising paper containing a wetting agent dis
tributed throughout its mass and having its spaces
and voids substantially completely ?lled with a
transparentizing water-soluble substance, where
by said paper is transparentized.
9. A transparent moistureproo?ng material
comprising paper containing a wetting agent dis
tributed throughout its mass and having its spaces
and voids substantially completely ?lled with a 70
transparentizing water-soluble substance where
by said paper is transparentized, said paper being
thinly coated with a transparent moistureproo?ng
.10. A transparent material comprising highly
" 2,108,808
calendered paper containing a wettin/g agent dis
tributed throughout its mass/and having its
spaces and voids substantially completely ?lled
with a water-soluble substance selected from the
class which consists of starch and starch com
pounds; .' '\
11. A transparent material comprising highly
calendered/paper containing a wetting agent dis
tributedthroughout its mass and having its spaces
10 and/voids substantially completely ?lled with
starch acetate.
/ 12. A transparent material comprising highly
calendered paper containing a wetting agent dis
tributed throughout its mass and having its
16 spaces and voids substantially completely ?lled
with chlorine-treated starch.
13. A transparent material comprising highly
calendered paper containing a wetting agent dis
tributed throughout its mass and having its spaces
20 and voids substantially completely ?lled with
oxidized starch.
14. A transparent material comprising highly
which consists of starch and starch compounds,
said paper being thinly coated on each side there
of with a transparent moistureproof composition.
15. A transparent material comprising highly
calendered paper containing a wetting agent dis
tributed throughout its mass and having its spaces
and voids substantially completely ?lled with
starch acetate, said paper being thinly coated on
each side thereof with a transparent moisture
prooi.’ composition.
16. A transparent material comprising highly
calendered paper containing a wetting agent dis
tributed throughout its mass and having its spaces
and voids substantially completely ?lled with
chlorine-treated starch, said paper‘ being thinly
coated on each side thereof with a transparent
moistureproof composition.
17. A transparent material comprising highly
calendered paper containing a wetting agent dis
tributed throughout its mass and having its spaces
and“ voids substantially completely ?lled with
oxidized starch, said paper being thinly coated on
calenderecl paper containing a wetting agent dis- ‘ each side thereof with a transparent moisture
tributed throughout its mass and having its spaces
and voids substantially'completely ?lled with a
water-soluble substance selected from the class
proof composition.
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