U.S. patent number 3,904,728 [Application Number 05/298,085] was granted by the patent office on 1975-09-09 for method of preparing fibrils having properties for making improved paper sheets.
This patent grant is currently assigned to Gulf Research & Development Company. Invention is credited to Joseph C. Davis, Francis R. Galiano, Robert W. Hill.
United States Patent |
3,904,728 |
Davis , et al. |
September 9, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Method of preparing fibrils having properties for making improved
paper sheets
Abstract
An improvement in the fibril formation process which includes
dissolving at an elevated temperature an olefin polymer having an
inherent viscosity of at least 3.5 in a hot hydrocarbon solvent,
shearing the hot polyolefin solution to thereby orient the polymer
molecules therein, passing the sheared solution through a cooling
zone maintained below the precipitation temperature of the solution
while maintaining the orientation of the polymer molecules within
the solution to thereby precipitate by thermal means the polymer in
the form of a solvent swollen fibrous mass, separating a
substantial portion of the polymer solvent from the fibrous mass,
beating the fibrous mass in a liquid which is a non-solvent for the
polymer and which is soluble in the polymer solvent for a time
sufficient to break down the fibrous mass into a plurality of
fibrils, and separating the fibrils from the nonsolvent liquid. The
improvement consists of incorporating from about 5 up to about 15
weight percent based on the weight of the polyolefin of a
surfactant selected from the group consisting of those nonionic
surfactants having an HLB value from 7 to 12 and those anionic
surfactants having an HLB value greater than 13 into the hot
polyolefin/hydrocarbon solvent solution prior to the fibril
formation steps of the process whereby the resultant fibrils
containing the surfactant possess improved hydrophilic properties
and paper sheets fabricated from these fibrils possess improved
physical properties, particularly increased tensile strength.
Inventors: |
Davis; Joseph C. (DeSoto,
KS), Galiano; Francis R. (Overland Park, KS), Hill;
Robert W. (Leawood, KS) |
Assignee: |
Gulf Research & Development
Company (Pittsburgh, PA)
|
Family
ID: |
23148959 |
Appl.
No.: |
05/298,085 |
Filed: |
October 16, 1972 |
Current U.S.
Class: |
264/140 |
Current CPC
Class: |
D21H
13/14 (20130101); D21H 5/202 (20130101); D21B
1/063 (20130101) |
Current International
Class: |
D21B
1/06 (20060101); D21B 1/00 (20060101); B02C
018/00 () |
Field of
Search: |
;264/8,5,140 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: White; Robert F.
Assistant Examiner: Hall; J. R.
Claims
What is claimed as new and what is desired to secure by Letters
Patent by the United States is:
1. In a process for preparing fibrils which may subsequently be
used to prepare paper sheets having improvements in tensile
strength, tensile factor and stretch properties, comprising:
a. forming a heated solution of an olefin polymer having an
inherent viscosity of at least 3.5 by dissolving said polymer in a
heated hydrocarbon solvent,
b. subjecting said solution to a shearing action whereby the
polymer molecules therein are oriented,
c. cooling said heated solution to a temperature below which said
polymer solute is made to precipitate in the form of a
solvent-swollen fibrous mass,
d. removing excess solvent from said fibrous mass,
e. cutting said fibrous mass into pieces of selected lengths,
and
f. beating said cut fibrous mass into individual fibrils,
the improvement consisting essentially of:
g. incorporating in said solution of step (a) about 2-20% by
weight, based upon said polymer, of a surfactant being partially
soluble in an amount of up to at least 2% by weight in said heated
solution, and being selected from the group consisting of nonionic
surfactants and anionic surfactants, said nonionic surfactants
having an HLB value from 7 to 12 and said anionic surfactants
having an HLB value greater than 13.
2. In a process as defined in claim 1 wherein said olefin polymer
is linear polyethylene.
3. In a process as defined in claim 2 wherein said linear
polyethylene has an inherent viscosity of at least 5.0 and is
present in said polyolefin/hydrocarbon solvent solution in an
amount of from about 0.25 up to about 5.0 weight percent and said
surfactant additive is a nonionic surfactant.
4. In a process as defined in claim 3 wherein said linear
polyethylene has an inherent viscosity of at least 10.0 and is
present in said polyolefin/hydrocarbon solvent solution in an
amount of from about 0.25 up to about 3.0 weight percent, said
nonionic surfactant additive is present in an amount of from about
5 up to about 15 weight percent based on the weight of said linear
polyethylene.
5. In a process as defined in claim 4 wherein said nonionic
surfactant is a surfactant selected from the group consisting of
alkylphenoxypoly (ethyleneoxy) ethanols, polyoxyethylene sorbitol
hexaoleates, polyoxyethylene sorbitan monooleates, polyoxyethylene
sorbitan tristearates, and poly(ethyleneoxy)sorbitan
monostearates.
6. In a process as defined in claim 2 wherein said linear
polyethylene has an inherent viscosity of at least 5.0 and is
present in said polyolefin/hydrocarbon solvent solution in an
amount of from about 0.25 up to about 5.0 weight percent and said
surfactant.
7. In a process as defined in claim 6 wherein said linear
polyethylene has an inherent viscosity of at least 10.0 and is
present in said polyolefin/hydrocarbon solvent solution in an
amount of from about 0.25 up to about 3.0 weight percent, said
anionic surfactant additive is present in an amount of from about 5
up to about 15 weight percent based on the weight of said linear
polyethylene.
8. In a process as defined in claim 7 wherein said anionic
surfactant is a surfactant selected from the group consisting of
diamyl ester of sodium sulfosuccinic acid, straight-chain
alkylbenzene sulfonic acids, and dioctyl ester of sodium
sulfosuccinic acid.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for the formation of improved
fibrils from high molecular weight polymers used to make improved
paper sheets fabricated from the resultant fibrils. More
particularly, the present invention pertains to an improvement, in
the method of making fibrils from very high molecular weight
polyolefins, particularly linear polyethylenes, whereby the
resulting fibrils and paper or other nonwoven sheet-like structures
into which these fibrils or fibril material are incorporated have
improved qualities. In greater detail, the subject invention is
concerned with a modification in the fibril-forming process from
very high molecular weight polyolefins, especially linear
polyethylenes, which includes the blending with the olefin polymer
of a certain, particular additive or modifier and then the
producing of improved fibrils from this polymer and additive blend,
which may then be fabricated into paper sheets possessing improved
properties. The fibrils produced by the invention, particularly
when employing the improvement therein, possess an improved
capability of forming coherent, self-supporting water leaves which
can be used for the production of paper and other nonwoven
sheet-like structures according to known methods of paper
manufacturing which possess improved properties.
2. Description of the Prior Art
During recent years, a need has developed throughout industry for a
better paper or paper product containing synthetic fibers of
improved quality. Several synthetic fiber paper compositions and
processes by which such fibers and paper can be made have been
proposed. For certain rather limited and specialized purposes, the
prior art compositions have been successful. However, because the
synthetic fibers containing these compositions are not at all
similar in structure to natural paper-making fibers, the
compositions have not been successful in the vast number of
situations where a product is required which has essentially
paper-like characteristics in addition to certain qualities not
found in natural fiber paper. Such papers should have improved
flexing qualities, high tensile and bursting strengths, both when
wet and dry, and be simply and economically produced.
The synthetic, hydrophobic fibers that were developed principally
for textile end uses are now being employed in the development of
numerous novelty and specialty papers, plus other nonwoven fibrous
products not traditionally associated with the paper industry.
Particular emphasis has been placed on the preparation of paper and
paper-like webs from these polymeric fibrous products either to be
ultimately used in unconverted form in specialty paper end uses or
to be combined with other materials as in a laminate structure for
its structural or aesthetic characteristics. To this end, for
obvious reasons, including availability and economy, it has been
advantageous to utilize conventional paper-making equipment and
techniques which are well known.
In Davis et al, Ser. No. 193,716, filed Oct. 29, 1971, entitled
"Improved Fibril and Process;" Davis et al, Ser. No. 202,302, filed
Nov. 26, 1971, entitled "Improved Fibril Process;" and Davis et al,
Ser. No. 211,562, filed Dec. 23, 1971, entitled "Fibril Process,"
all now abandoned, there have been disclosed a number of processes
or methods for producing high quality fibrils which are especially
suitable for and readily adaptable to incorporation into paper or
other nonwoven sheet-like structures which may be manufactured by
known paper-making processes. The invention disclosed herein
relates to changes or modifications in those fibril and
paper-making processes which result in improvements in the produced
fibrils and in the paper or other nonwoven sheet-like structures
fabricated from these improved fibrils produced by those
processes.
In each of those previously mentioned processes, fibrils are
produced from a solution of a very high molecular weight
polyolefin, such as polyethylene or polypropylene and more
particularly linear polyethylene, in which the solution is sheared
or subjected to a shearing action whereby the polymer molecules
therein are oriented and immediately thereafter the polymer solute
is made to precipitate from the solution by purely thermal means,
which is attained by rapidly lowering the temperature, as in a
quenching bath or by other cooling means. As set forth therein, the
most useful systems for this type of fibril production are those
systems employing polyolefins and suitable liquid hydrocarbon
solvents for theses polyolefins. The cooling or quenching of these
oriented solutions is usually carreid out under conditions of zero
shear and at temperatures well below the precipitation temperatures
of the polymer solutions to result in the formation of solvent
swollen fibrous masses. These fibrous masses are then normally
converted into fibrils by a series fo subsequent operations which
may and usually do include the removal of excess solvent from the
fibrous mass, the cutting of the fibrous mass into pieces of
desired length, and the bearing and refining of the cut or chopped
fibrous mass into individual fibrils for use in the production of
paper or other nonwoven sheet material on paper-making machinery by
the normally employed methods and techniques of paper
production.
While the papers or other nonwoven sheet-like structures fabricated
in each of the hhereinabove-identified disclosures, from a
plurality of the fibrils produced by the process of each of the
respective inventions, and the fibrils themselves, are of good
quality, it has been observed that some of the physical properties
of the fibrils and the paper sheets so produced were somewhat less
than might be desired and could stand improvement. It would be
desirable, and it is the general object and concern of this
invention, to produce fibrils and paper sheets from synthetic
polymers by the processes set forth in the above-identified
disclosures which possess improved physical properties when
compared to the physical properties of the fibrils and paper sheets
produced in those disclosures. It is particularly desirable to
produce fibrils from purely synthetic or man-made materials and
paper sheets fabricated therefrom which, respectively, possess
improved hydrophilic properties, are more readily
water-dispersible, are more readily adaptable to use in
conventional paper-making equipment utilizing the normally employed
methods and techniques of paper production, and possess improved
tensile strength, burst strength, elongation and fold endurance
when compared to the previously produced fibrils and fabricated
paper sheets from these type materials.
SUMMARY OF THE INVENTION
We have found that fibrils and paper, or other similar nonwoven
sheet-like structures, of higher quality and possessing improved
properties over those fibrils and paper sheets fabricated in the
hereinabove-identified disclosures, can be proudced if a minor
amount of a certain additive or modifier is incorporated into the
starting hot polyolefin/hydrocarbon solvent solution from which the
fibrils that are to be incorporated into the paper sheets are
formed prior to the fibril formation steps of the process. By the
incorporation of minor amounts of the additive or modifier, the
resultant fibrils are more hydrophilic and more readily
water-dispersible; and paper sheets fabricated therefrom possess
improved properties, such as higher tensile strength, increased
burst strength, increased stretch and greater fold endurance, and
are generally of a higher quality and grade. The particular
additive or modifier incorporated into the starting or beginning
polymer solution is a surfactant. The particular surfactant
incorporated may be a nonionic surfactant or an anionic surfactant.
The nonionic surfactant employed should have an HLB value or number
of from about 7 up to about 12, and the anionic surfactant used
should have an HLB value or number greater than 13. The additive
surfactant may be incorporated at levels of from about 2 weight
percent up to about 20 weight percent based on the weight of the
high molecular weight polyolefin, particularly linear polyethylene,
added to the hydrocarbon solvent of the beginning solution, to
impart the desirable improvements to the resultant fibrils formed
during the process and the paper sheets fabricated therefrom. More
particularly, it is preferred to incorporate in the range of from
about 5 up to 15 weight percent of the modifying surfactant to
impart the desired increase in hydrophilic properties of the
fibrils and the higher quality and grade to the resultant paper
sheets.
DETAILED DESCRIPTION
In order that the complete fibril formation process and the method
of fabrication of paper sheets therefrom is completely and readily
understood, the disclosure of Davis et al, Ser. No. 193,716 (more
completely identified hereinabove) is incorporated herein by
reference.
By the invention disclosed herein, paper sheets or other similar
nonwoven sheet-like structures may be fabricated from improved
fibrils which are formed or obtained from a process or method like
that disclosed in Davis et al, Ser. No. 193,716, from wholly
man-made or synthetic polymeric materials which fibrils and sheets
possess improved properties and are of a better or higher quality
and grade than those fibrils and sheets obtained in the
previously-identified disclosures. The invention contemplates the
addition of a certain, particular additive or modifier material to
the polyolefin and hydrocarbon solvent beginning solution prior to
the formation of fibrils therefrom by one of the processes set
forth in the hereinabove-identified disclosures. The modifier or
additive incorporated into the polyolefin and solvent solution is
incorporated in minor amounts to attain the unexpected and desirous
improvements in the resultant fibrils and improvement in many of
the physical properties of the paper sheets formed from the fibrils
produced. The additive employed is a surfactant and is employed at
levels of from about 2 weight percent up to about 20 weight
percent, and preferably from about 5 up to about 15 weight percent
based on the amount of the polyolefin, particularly high molecular
weight linear polyethylene, dissolved in the hydrocarbon solvent to
form the starting solution. The surfactant incorporated may be a
nonionic surfactant or an anionic surfactant.
The nonionic surfactants which are effective in this invention are
those with an HLB number or value between 7 and 12. The "HLB", or
hydrophilic-lipophilic balance, refers to the relative degree of
water solubility and oil solubility of an emulsifier or surfactant;
these properties determine the usefulness of a given surfactant for
a particular chemical system. The HLB is described on a scale from
1 to 20, an HLB number of 1 indicating a highly oil-soluble
surfactant, and a value of 20 indicating a high degree of water
solubility. As indicated above, the nonionic surfactants which
perform well in this invention have HLB values between 7 and 12.
Those which lie outside this range either do not disperse the
polymer fibers well in an aqueous medium, are insufficiently
soluble in the kerosene (Speedsol) solvent, or do not impart
desirable properties to the finished paper.
The HLB system applied to anionic surfactants gives somewhat
different results. In this case, the best results have been
obtained where the surfactant is quite soluble in water, i.e., the
HLB number or value is greater than 13. The fact that the HLB
requirements for this invention for anionic surfactants is quite
different than for nonionics is not surprising, since the ionic
nature of the former changes their water solubility relative to the
nonionics to a much greater extent than it effects the oil
solubility. Reasons for this are discussed in the publication, "The
Atlas HLB System", 2nd edition, 1963, published by Atlas Chemical
Industries, Inc. This publication also describes (p. 19) a method
for determining the HLB values or numbers for anionic surfactants
-- the water-dispersibility method -- which has been used for
determining the values reported herein.
The HLB values or numbers reported herein for the nonionic
surfactants were obtained from "McCutcheon's Detergents and
Emulsifiers Annual", 1972, published by McCutcheon's Division,
Allured Publishing Corp., Ridgewood, N. J.
Among those additive or modifier surfactants which have been used
in this invention and successfully incorporated into the beginning
polyolefin and hydrocarbon solvent solution to impart the
unexpected and desirable improvements in the resultant fibrils
produced during the process and the paper sheets fabricated
therefrom are the following:
Igepal CO-210, nonylphenoxypoly(ethylneoxy)ethanol, a nonionic
surfactant obtained from GAF Corporation, having an HLB value of
7.0.
Atlas G-1086, polyoxyethylene sorbitol hexaoleate, a nonionic
surfactant obtained from Atlas Chemical Industries, having an HLB
value of 10.2.
Aerosol AY, diamyl ester of sodium sulfosuccinic acid, an anionic
surfactant obtained from American Cyanamid Company, having an HLB
value greater than 13.0.
Conoco SA-697, straight-chain tridecylbenzene sulfonic acid, an
anionic surfactant obtained from Continental Oil Company, having an
HLB value greater than 13.0.
Tween 81, polyoxyethylene sorbitan monooleate, a nonionic
surfactant obtained from Atlas Chemical Industries, having an HLB
value of 10.0.
Tween 65, polyoxyethylene sorbitan tristearate, a nonionic
surfactant obtained from Atlas Chemical Industries, having an HLB
value of 10.5.
Aerosol OT, dioctyl ester of sodium sulfosuccinic acid, an anionic
surfactant obtained from American Cyanamid Company, having an HLB
value greater than 13.0.
Tween 61, poly(ethyleneoxy)sorbitan monostearate, a nonionic
surfactant obtained from Atlas Chemical Industries, having an HLB
value of 9.5.
Igepal CO-430, nonylphenoxypoly (ethyleneoxy)ethanol, a nonionic
surfactant obtained from GAF Corporation, having an HLB value of
11.0.
The additive or modifying surfactant may be added to the
hydrocarbon solvent when the same is hot or prior to the heating
thereof and may be added thereto along with the high molecular
weight linear polyethylene, prior thereto or after the linear
polyethylene has been dissolved in the hydrocarbon solvent. In
order to be useful in this invention, the surfactant should be
soluble to a degree in the hot polyolefin/hydrocarbon solvent
solution but not overly soluble therein. The surfactant must be
soluble in an amount of up to at least 2 percent on a weight basis
in the hot polyolefin/hydrocarbon solvent solution to be employable
in the invention.
In order to illustrate the invention and the improvments in the
resultant fibrils and the paper sheets improvements from the
fibrils produced with greater particularity, the following specific
examples are included. These examples are intended to be
illustrative of the invention only and are not intended to limit
the same in any way.
EXAMPLE 1
In this example, fibrils were produced by the process set forth in
Ser. No. 193,716 (more completely identified hereinabove) without
employing the improvement of this invention, and the resultant
fibrils were used to fabricate paper sheets on the Noble and Wood
sheet-forming machine, physical properties of which were measured
and are set forth hereinbelow. This example is included as a
control for comparative purposes with the fibrils prepared in
accordance with the invention and the improvement thereof and with
the paper sheets fabricated from these improved fibrils.
A glass vessel equipped with a stirrer was charged with 3.0 liters
of the substantially aliphatic hydrocarbon solvent Speedsol
(boiling range 155.degree.-180.degree. C.) containing 0.018 gram of
an anti-oxidant mixture consisting of equal parts by weight of
Ionol, Santonox R (trademarks) and dilauryl thiodipropionate. The
solvent/anti-oxidant mixture was heated to 150.degree. C. and then
15.0 grams of a linear high molecular weight polyethylene, having
an inherent viscosity of approximately 13 was added; the inherent
viscosity of the polymer being defined by the formula:
Inherent Viscosity = ln t/t.sub.o /c
wherein t = fall time or time for passage through the viscosimeter
of the polymer solution, t.sub.o = fall time of the solvent and c =
concentration of the polymer in the solvent. All inherent viscosity
measurements set forth herein are made at a concentration of 0.05
gram of polymer per 100 milliliters of decalin at 135.degree.
C.
The slurry was held at the 150.degree. C. temperature with stirring
for a time period sufficient to completely dissolve the
polyethylene and result in a solution suitable for the formation of
fibrils by the methods of the hereinabove-identified disclosures.
This solution was then charged to a centrifugal spinning apparatus,
such as the hammermill shown at reference numeral 22 in Ser. No.
193,716, whose rotor was rotating at approximately 11,140 rpm.
Fibrils suitable for paper production were then produced by
carrying out the remainder of the method steps set forth in the
process of Ser. No. 193,716 wherein the temperature of the fibrils
coming from the spinning apparatus was -10.degree. C. and the
refining was carried out in isopropanol in a Waring blender. The
fibrils were used to make paper sheet which were obtained by
slurrying the fibril product produced to the head box of the Noble
and Wood sheet-forming machine. Handsheets were then formed on the
Noble and Wood machine by the usual and normal methods employed in
the use of this sheet-forming machine. A number of physical
properties of the resultant sheets formed in this example were
determined and calculated and are set forth hereinbelow in Table
I.
Water-dispersibility studies for the fibrils produced in this and
the following examples were undertaken and results thereof are set
forth hereinbelow in Table II. The dispersiblity in water of the
fibrils obtained in the examples was checked by dispersing 3.0
grams (weight of a squeezed but not dried sample of the fibrils) of
fibril pulp in 250 milliliters of water in a Waring blender.
The fibril pulp derived from purely linear high molecular weight
polyethylene without any additives or modifiers (Example 1) is
almost completely unwet and the essentially dry fibril pulp floats
on the surface of the water in a Waring blender. The varying
degrees of improvement attained with the various modifiers or
additives of the invention were readily apparent when fibril pulp
samples of the same were dispersed as above in 250 milliliters of
water in a Waring blender.
In order to attain some numerical comparisons of the dispersibility
of the fibril pulp obtained from the various blends of high
molecular weight linear polyethylene and the various surfactant
additives, the water and pulp suspension obtained in the Waring
blender for each of the examples was transferred to a 250
milliliter graduated cylinder and the water level adjusted to 250
milliliters. If there was any of the substantially dry fibrils in
the pulp, the approximate fraction of the substantially dry fibril
material was noted and is recorded hereinbelow in Table II. As can
be noted from the table, substantially dry fibrils within the pulp
are greatest when the poorest of blends of the additive or
modifying surfactants are employed.
The next step in the dispersibility study was to vigorously shake
the suspension in the graduated cylinder and thereafter note and
record the volume occupied within the graduated cylinder by the wet
pulp after time intervals of 30 seconds, 60 seconds and 10 minutes.
The values observed and recorded are reported hereinbelow in Table
II.
Yet another measure of the fibril pulp's dispersibility undertaken
in these water-dispersibility studies was that of the rise time of
the fibril pulp. The rise time of the fibril pulp was observed and
recorded at two different levels within the 250 milliliter
graduated cylinder after the suspension therein had been vigorously
shaken. The two levels within the graduated cylinder at which the
times were observed and recorded were the 100 milliliter level and
the 80 milliliter level. The time required for the wet pulp volume
within the graduated cylinder to reach or decrease to 100
milliliters and also to 80 milliliters were recorded and are
reported hereinbelow in Table II.
EXAMPLE 2
In this example, fibrils and paper sheets fabricated therefrom were
prepared by the process set forth in Ser. No. 193,716 and as set
forth in Example 1 employing the improvement of the invention,
i.e., the addition of a modifying surfactant to the starting or
beginning polymer solution from which the improved fibrils are
formed.
The apparatus employed and the process used in this example were
identical to that used in Example 1 with the exception that an
additive, a nonionic surfactant, was used and added in a minor
amount to the starting hot polyethylene/hydrocarbon solvent
solution.
The vessel used in Example 1 was charged with 3.0 liters of
Speedsol solvent containing 0.018 gram of the anti-oxidant mixture
of Example 1 to which 1.5 grams of Igepal CO-210
(nonylphenoxypoly(ethyleneoxy)ethanol, a nonionic surfactant
obtained from GAF Corporation, having an HLB value of 7.0) was
added. This mixture was then heated to 150.degree. C. To the
resulting Speedsol solvent/additive surfactant solution was added
15.0 grams of a linear high molecular weight polyethylene having an
inherent viscosity of 13.33. This mixture was then held with
stirring at the 150.degree. C. temperature for a time sufficient to
completely dissolve the polyethylene, thereby resulting in a
solution suitable for the formation of fibrils by the method set
forth in Example 1, and containing about 10 weight percent of the
surfactant additive based on the weight of the linear polyethylene.
Water-dispersibility studies, as in Example 1, were carried out on
the fibrils produced by the method set forth in Example 1, and
these fibrils were used to make paper sheets on the Noble and Wood
sheet-forming machine as was done in Example 1. Some of the
physical properties of the resultant sheets fabricated in this
example were obtained and are recorded in Table I below, and the
data collected in the water-dispersibility studies are reported in
the following Table II.
EXAMPLE 3
In this example, fibrils were prepared and refined by the methods
and procedures carried out in Examples 1 and 2 and paper sheets
were prepared therefrom in the manner identical to that employed in
Examples 1 and 2 with a single exception. In this example, the
additive or modifying surfactant employed was a different
surfactant but was employed at the same level or concentration. The
nonionic surfactant used was Atlas G-1086 (polyoxyethylene sorbitol
hexaoleate, a nonionic surfactant obtained from Atlas Chemical
Industries, having an HLB value of 10.2) and was employed in an
amount of 1.5 grams in 3.0 liters of the Speedsol solvent of
Example 1. The resultant Speedsol solvent/surfactant
additive/linear high molecular weight polyethylene solution
contained approximately 10 weight percent of the surfactant
additive based on the weight of the linear polyethylene. Fibrils
were then produced by the method set forth in Examples 1 and 2,
water-dispersibility studies were carried out as in Example 1, and
paper sheets were prepared from the fibrils as was done in Examples
1 and 2. The physical properties of the resultant sheets fabricated
on the Noble and Wood sheet-forming machine was determined and are
recorded hereinbelow in Table I, and the data collected in the
water-dispersibility studies are reported in the following Table
II.
EXAMPLE 4
Fibrils were prepared and refined by the methods and procedures
carried out in Example 2 and paper sheets were prepared therefrom
in a manner identical to the employed in Example 2 with the
exception that the additive or modifying surfactant employed was a
different surfactant. The surfactant used was Aerosol AY (a diamyl
ester of sodium sulfosuccinic acid, and anionic surfactant obtained
from American Cyanamid Company, having an HLB value greater than
13.0), which was employed in an amount of 1.5 grams. The resultant
solvent/surfactant/linear high molecular weight polyethylene
solution contained about 10 weight percent of the surfactant
additive based on the weight of the linear polyethylene. Fibrils
were then produced from this solution by the processes set forth in
Examples 1 and 2, water-dispersibility studies were undertaken and
carried out on the fibrils as in Example 1, and paper sheets were
fabricated from the resultant fibrils as was done in Examples 1 and
2. The physical properties of the paper sheets fabricated on the
Noble and Wood sheet-forming machine were determined and are
reported in the following Table I, and data collected in the
water-dispersibility studies were recorded and are set forth
hereinbelow in Table II.
EXAMPLE 5
In this example, fibrils were parepared and refined in a fashion
similar to that employed in Example 2 and paper sheets were
prepared therefrom in a manner identical to that employed in
Example 2, with the exception that a different surfactant additive
was used and was employed at the same level or concentration. The
surfactant additive used was Conoco SA-697 (a straight-chain
tridecylbenzene sulfonic acid, an anionic surfactant obtained from
Continental Oil Company, having an HLB value greater than 13.0) and
was employed in the amount of 1.5 grams. The resulting
solvent/surfactant additive/linear high molecular weight
polyethylene solution contained approximately 10 weight percent of
the surfactant additive based on the weight of the linear
polyethylene. Fibrils were thereafter produced by the method set
forth in Examples 1 and 2, water-dispersibility studies of the
fibrils were undertaken as in Example 1, and paper sheets were
fabricated from the resultant fibrils as was done in Examples 1 and
2. The physical properties of the resultant sheets prepared on the
Noble and Wood sheet-forming machine were determined and are set
forth herienbelow in Table I and the results of the
water-dispersibility studies are recorded in the following Table
II.
Table I
__________________________________________________________________________
Example Example Example Example Example Property* 1 2 3 4 5
__________________________________________________________________________
Basis Weight 45.15 40.46 52.48 50.70 56.14 lbs./3000 ft..sup.2
Tensile Strength, 5.50 9.40 12.57 7.19 10.02 pli Tensile Factor
0.12 0.23 0.24 0.14 0.17 Stretch, % 4.78 21.70 20.00 9.57 12.30
Elmendorf Tear, 182.00 148.00 178.00 324.00 147.00 g./sheet
Elmendorf Tear 4.04 3.66 3.56 6.10 2.74 Factor
__________________________________________________________________________
*Tappi Procedure No. T220?
Table II ______________________________________ Time (sec.)
Required for Volume (ml) Volume of Wet % Dry of Wet Fibrils Fibrils
to Fibrils After Decrease to Exam- On Water 30 60 10 100 80 ple
Surface sec. sec. min. ml. ml.
______________________________________ 1 90 5 5 5 <1 <1 3
trace 95 90 75 15 360 5 60 60 50 1 2 4 30 20 20 20 <1 <1 5 5
60 55 55 3 4 ______________________________________
As can be readily observed from the above Tables I and II and a
study and comparison of the results recorded therein, the practice
of this invention and the improvement thereof, i.e., the
incorporation of a minor amount of an additive or modifying
surfactant into the beginning or starting solution from which the
fibrils are formed, results in improved hydrophilic properties in
and improved water-dispersibility of the fibrils produced and in
improved and increased physical properties in the resultant paper
sheets fabricated from saids fibrils. By a comparison of the
examples set forth in Tables I and II above, it is readily seen
that the fibrils produced possess improved hydrophilic properties
and that many of the physical properties of the resultant paper
sheets prepared from these fibrils are increased and improved by
modifying the high molecular weight linear polyethylene/hydrocarbon
solvent solution from which the fibrils are formed and sheets are
fabricated by the addition of a minor amount of a surfactant
additive. The improvement in quality and grade of the resultant
sheets is particularly evident in the increase in tensile strength,
as indicated by the tensile factor and the stretch.
Obviously, numerous modifications and variations of the present
invention are possible in light of the above teachings. It is,
therefore, to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described therein.
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