Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
GLASS FIBER SEPARATORS FOR BATTERIES
EACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates generally to the field of batteries and, more
specifically, to separators containing glass fibers which are positioned
between the positive
and negative plates of batteries and to a method for producing such
separators. As is
subsequently discussed in more detail, separators containing glass fibers are
well known.
Long before glass fiber separators, however, cedar veneers were used as a
separator
material, and were replaced by microporous, hard rubbery separators and
cellulose
separators impregnated with resins.
DESCRIPTION OF THE PRIOR ART
Valve regulated ("sealed" - "recombinant") lead acid (VRLA) batteries are
known;
they usually comprise a plurality of positive and negative plates, as in a
prismatic cell, or
layers of separator and positive and negative electrodes wound together, as in
a "jelly roll"
cell. The plates are arranged so that they alternate, negative - positive -
negative, etc.,
with separator material and paste separating each plate from adjacent plates.
The
separator, which, typically, is a mat of glass fibers, is an inert material;
it stores battery
acid, applies a force to paste-grid interfaces, and provides low electric
resistance. In
addition, in VRLA batteries, there arc innumerable gas channels in the
separator material
through which oxygen can migrate from the positive electrode, when generated
there, to
the negative electrode where it can be recombined with hydrogen, according to
the oxygen
cycle. One of the most important functions of a separator in a VRLA battery is
to force
the paste into contact with the plates, and cause a pressure between the
plates.
Glass fiber separator material, typically, is produced commercially on paper
making equipment including fourdrinier machines and rotoformers, inclined
fourdrinier
machines and extended wire rotoformers. In the production of separator made of
glass
fibers for VRLA batteries, it is preferred that no organic material be added
to a furnish
from which separator sheets are made; the entanglement of individual fibers
serves to
maintain the sheet in a cohesive structure, and water glass, which sometimes
forms on the
fiber surfaces, serves as a binder. Organic binders, however, tend to decrease
the ability
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of a separator to wick acid, and to decrease the amount of acid a separator
can hold. A
great deal of work has been directed to modifying the glass fiber furnish from
which
separators are produced to improve battery performance and/or lower the cost
of the
separator. Some of the work has entailed the addition of synthetic fibers for
various
S_ reasons, such as the use of thermoformable plastic fibers so that the
separator can be heat
sealed on its edges to envelop a plate. Other work, which pertains to the
field of this
invention, has been directed to the use of filler, e.g., silica, to provide
separators which
are comparable to all glass fiber separators, at a lower cost. Separators made
from glass
fibers to which cellulose has been added and polyolefin fibers to which
cellulose has been
added have also been suggested. Prior art patents are discussed below.
US Patent No. 4,465,748 (Harris) discloses glass fiber sheet material for use
as a
separator in an electrochemical cell, and made from 5 to 35 percent w/w of
glass fibers
less than 1 pm in diameter; the patent also discloses a glass fiber sheet for
such use
wherein there are fibers of a continuous range of fiber diameters and lengths,
and most
of the fibers are not over 5 mm in length.
US patent No. 4,216,280, (Kono et a1.), discloses glass fiber sheet material
for use
as a plate separator in a battery, and made from 50 to 95 percent w/w of glass
fibers less
than 1 p.m in diameter and 50 to 5 percent w/w of coarser glass fibers. The
coarser glass
fibers, the reference says, have a fiber diameter larger than 5 pm, preferably
larger than
10 Vim, and it is advantageous for some of the coarser fibers to have
diameters of 10- pm
to 30 wm.
US Patent No. 4,205,122 (Minra et al) discloses a battery separator of reduced
electric resistance comprising a self supporting, non woven mat consisting
essentially of
a mixture of olefinic resin fibers having a coarseness of from 4 to 13
decigrex and
olefinic resin fibers having a coarseness of less than 4 decigrex, the latter
fibers being
present in an amount of not less than 3 parts by weight per 100 parts by
weight of fibers;
up to about 600 parts by weight of inert filler materials per 100 parts by of
fibers can also
be used. The battery separator is produced by subjecting a suitable aqueous
dispersion to
a sheet-forming operation, drying the resulting wet, non-woven mat, and heat
treating the
dried mat at a temperature ranging from a point- 'Z0° lower than the
melting point of the
aforementioned fibers to a point about 50° higher than the melting
point.
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US Patent No. 4,216,281 (O'Rell et al.) discloses a separator material
produced
from a furnish containing 30 to 70 percent w/w of polyolefin synthetic pulp,
15 to 65
percent w/w of a siliceous filler and 1 to 35 percent w/w of "long" fibers
which can be
polyester fibers, glass fibers, or a mixture of the two. Cellulose in an
amount up to about
percent w/w is disclosed as an optional ingredient of the furnish.
US Patent No. 4,363,856 (Waterhouse) discloses a separator material made from
a furnish composed of polyolefin pulp fibers and glass fibers, and names
polyester staple
fibers, polyolefin staple fibers and cellulose pulp fibers as alternative
constituents of the
furnish.
10 US Patent No. 4,387,144 (McCallum) discloses a battery separator having a
low
electrical resistance after extended use which is made by thermal
consolidation and
thermal embossing of a paper web formed from a furnish containing a synthetic
pulp the
fibrils of which are filled with an inorganic filler, the web incorporating a
wetting agent
which is preferably an organic sulphonate, and organic succinate, or phenol
ethoxylate.
US patent No. 4,373,015 (Peters et al.), discloses sheet material for use as a
separator in a battery, and "comprising organic polymeric fibers"; both of the
examples
of the reference describe the sheet material as "short staple fiber polyester
matting about
0.3 mm thick", and indicate that the polyester fibers range from about 1 p.m
to about 6
p,m in diameter.
~0_ Sheet separators for use in conventional (not valve regulated) batteries
and
comprising both glass fibers and organic fibers are disclosed in all of the
following US
patents: No. 4,529,677 (Bodendorf); No. 4,363,856 (Waterhousc); and No.
4,359,511
(Strzempko).
US patent No. 4,367,271, Hasegawa, discloses storage battery separators
composed
of acrylic fibrils in an amount of up to about 10 percent w/w, balance glass
fibers.
Japanese patent document 55/146,872 discloses a separator material comprising
glass fibers (50-85 percent w/w) and organic fibers (50-15 percent w/w).
US patent No. :1,245,013, Clegg et al., discloses a separator made by
overlaying
a first sheet of fibrous material including polyethylene fibers with a second
sheet of
30 fibrous material including polyethylene and having a synthetic pulp content
higher than
the first sheet.
US Patent No. 4,908,282, Badger, discloses a separator comprising a sheet made
from first fibers which impart to the sheet an absorbency greater than
90°~o and second
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fibers which impart to the sheet an absorbency less than 8(1% wherein the
first and second
fibers are present in such proportions that the sheet has an absorbency of
from 75 to 95%.
This patent discloses that fine glass fibers have a high absorbency. that
coarse glass fibers
have a low atuorbency, and that hydrophobic organic fibers have an cxtrcmet)~
low
absvrbeney, and that, when this separator is saturated with clcxtrolyte,
unfilled voids
remain so that gas can transfer from plate to plate for recombination.
US Patent No. 5,091.275 (F3rccht ct at.) discloses a glass fiber separator
which
expands when exposed to electrolyte. Tile separator comprises eiass fibers
which arc
LQ impregnated with an aqueous solution of colloidal silica particles and a
sulfate sail. The
separator is produced by forming a paper making web of glass filxrs,
impregnating the
web with the aqueous mixture of silica and the salt, lightly comprcwing the
impregnated
web to remove some of the aqueous solution, partially drying tttc web,
compressing the
web to a final thickness and completing the drying of the web. Tltc web is
preferably
compressed to a thickness which is less than the distance het~~ecn plates in a
given cell,
so that insertion of an assembled cell stack into a case is facilitated. When
electcol~~te is
added to the case. the salt dissolves in the electrolyte and the sepuator
expands to provide
good contact between the plates and the aepantors. According to the patent,
the silica
contributes to the recombination performance of cells incorporating the pre-
compressed
,~,~ separator. The silica also contributes a great deal of stiffness to Ihc
separator, so much so
that the separator may be characterized as rigid.
It has been determined that the production of battery separator by paper-
making
techniques fmm a furnish of glass fibers and silica powder leads to problems
wttich arc
caused by variations in the concentration of the silica powder in the furnish.
Typical glass
fiber furnishes have a liquid content exceeding 9R percent wIN~. In the course
of making
separator sheets, most of the w:ttcr is removed from the furnish in the first
few feet of a
screen on which the furnish is cast. The water, known as white water, is
recycled and
winds up back in the hcadhox of the machine. If the furnish is composed
exclusively of
glass fibers, virtuall~~ none of the fibers pass through the wire and wind up
in the white
~Q water. However, furnishes comprising glass fibers and silica powder do not
fare so well.
In the absence of a retention aid, significant amounts of silica powder from
such furnishes
do pass through the paper making wire :uuf wind up in the white mater. Left
unchecked,
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this phenomenon causes the concentration of silica powder in the furnish to
increase,
undesirably changing the properties of the furnish. Heretofore, the problem of
silica
powder and the like passing through a paper making wire has hecn avoided
through the
use of binders as retention aids.
US patent No. ?,477,0(H) discloses a syntltctic fiber papa prcxluccd from
fibrillae
and fibers made by methods wherein a solution of the fiber is extruded through
very
small orifices (spinnerets) and then the extruded solution is altowcd to
congeal either in
a precipitating bath or by evaporation of the soUcnt or by temperature changes
(see
column 2, lines 25 and foitowing). The patent says that fibers of cellulose
acetate,
LQ cellulose nitrate, regenerated cellulose from viscose, *Vinylitc (a
synthetic resin made by
polymerization of vim~l compounds).~'Aralac (a fibrous product made from skim
milk
casein), and spun glass" which range in length from '/~ inch to I inch and in
diameter
from 1?.-80 microns and fibriilac prcfcrahly derived from flat, Manila hemp,
caroa or
hemp can be used to make the paper. At Icwt ~)t) pcrccn t of the fibrillac
should he from
O.U015 to O.t~25 inch in length and from tf.tHHHH)37 to O.iHI()pU4d inch in
width.
BRIEF DESCRIPTION Q~'LEf>t1_N_SMAN.~IN~NT10N
The instant invention is based upcm the discovery that comparatively small
additions of wood pulp, if beaten or refined to a sufficient degree to product
a highly
fibrillated cellulose fiber, to a glass fitxr furnish witable for use in
making battery
,?~Q separator material,
(l) cause surprisingly high incrca~es in some of the strength pmpctties of
separator made from the furnish.
(3) impmvc the cut through resistance of , separator made from the
furnish.
(3) and have a unique characteristic in that they hold a greater proportion
of acid introduced thereunto when the separator is subsequently
compressed.
In addition, the separator is repulpahle, in the sense that it can he used as
a constituent
of a glass fiber which is used to prc~ducc ~new" separator; furthermore,
batteries made
from glass fiber separator material which contaitte comparatively small
amounts of wood
pulp which has been beaten or refined so a sufficient degree, have remarkably
long service
lives, as indicated by their performance in cycling tests. In general, the
pulp slurry should
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be beaten or rE:fined to a Canadian freeness not greater than
about 650 cc, or to an equivalent freeness by other
measurement te<:hniques, :~.nd a remarkablEv increase in tensile
strength is achieved wren the pulp is beaten or refined to a
Canadian freenE:ss not c~rf;~:~ter than about 120 cc, or to an
equivalent freE:ness by otaer measurement techniques.
Thus, in one aspect the invention provides a glass
fiber separator material. comprising a mass of. intermeshed
glass fibers substantia~lvy all of which have a fiber
diameter not greater than ak~>out 20 um, and at least 5
percent w/w of which havre a fiber diameter less than 1 um,
and, distributed through the glass fibers, from 0.2 percent
w/w to 20 percent w/w ct~~_:Lulose pulp beaten to a Canadian
standard freeness not g=r_eater than 120 <~c~..
In a second aspect, there is provided a sealed
lead/sulfuric acid recombinant storage battery comprising a
plurality of lead plates in a closed care, a glass fiber
separator material as df-.:~cribed i:n the first aspect between
adjacent ones cf said p:Lates, and a bady of a sulfuric acid
electrolyte absorbed by said glass fiber separator material
and maintained in contacts: with each of tre adjacent ones of
said plates.
' I' . ,
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BRIEF Dl~ CRI ON OF THE DRAWINGS
Fig. 1 is a plot of the percent w/w of added cellulose in glass fiber
separator
material according to the invention vs. the liters per second of air flowing
through the
separator material under test conditions that arc subsequently described
herein.
Fig. ? is a plot of tensile strength, lx~th machine direction ("Tensile, MD")
and
cross direction ("Tensile, CD"), vs. percent w/w of added cellulose in glass
fiber battery
separator according to the invention.
Fig. 3 is a plot of percent of initial capacity vs. number of test cycles for
a battery
according to the invention and for a control battery.
Figs. ~ through 9 arc plots of thickness (the values plotted are 1000 times
the
thickness of the separator in mm) vs. load and rebound thickness vs. load for
fide glass
fiber separator materials according to the in4~entinn and a control, where
rebound thickness
is 1000 times the thickness of a separator material in mm after that separator
has been
subjected to a load and the load has been reduced to 0.55 pounds per square
inch (3.79
ICPa); the data in Figs. 4 through 9 are for dry separator material.
2S2 Figs. 10 through 15 are plots similar to those of Figs. 4 through 9,
showing
thickness vs. load and rebound thickness ~s. load for the five glass fiber
separator
materials according to the invention and for the control, but arc based cm
data where,
before testing. each of the separator materials had been wet with seven times
its weight
of sulfuric acid hating a specific gravity of 1?86.
Figs. 1G and 17 are plots similar to Figs. ~1 and S, differing in that
interpolated
points are plotted in the former, so that successive points along the X axis
represent equal ;
increments of cellulose content; while experimental values arc plotted in the
latter and,
as a consequence, as is subsequently explained herein, successive points along
the X axis
do not always represent equal increments of cellulose content.
~f DEFINITIONS
. Subsequently herein, the.term "percent v/v" means percent by volume; the
term
"percent w/w" and the symbol 'fin mean percent by weight: the term "wire", as
applied to,
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a paper making machine, means the surface of the machine cm which a furnish is
cast in
producing paper, amd can be, for example, the screen of a Fourdrinier machine
or the
vacuum drum of a rotoformcr machine; p()rC S1ZCS rCp(1('ICd llCTe111, unless
otherwise
indicated, arc in microns, and arc determined by the first bubble method or by
liquid
porosimetry, Coultcr: alt temperatures arc in °C.; and the followinb
ahbrcviations have the
meanings indicated: Erm = micron or microns; mg=milligram or milligrams:
g=gram or
grams; kg=kilogram or kilograms; 1=liter or liters; mi=milliiitcr or
milliliters; cc=cubic
centimeter or cubic centimeters; pef=pound per cubic foot or pounds per cubic
foot;
m=meter or meters; cm=centimeter or centimeter; mm=millimeter or millimeters;
LQ m=meter or meters; mil=inch x t()'' or inches x 10'' (multiply times
'_'S.:1 to convert to
mm); KPa=pressure in thousands of Ncwtons per square meter: psi=pounds per
square
inch (multiply time. C~.R~> to convert to KPa); and KN=force in thousands of
'Jcwtons.
EXAMPLE 1
Glass fiber separator hand sheets were produced in a lalxlrator~~ apparatus by
y~ depositing a furnish on a wire or screen, and draining the furnish. The
apparatus
comprised a tank with a screen in the bouom, a drain below the screen, a ualvc
which
opened and closed tilt drain, and a hand paddle which was moved back and forth
to
simulate the movement of a furnish in commercial papcrmaking apparatus and
establish
a "machine direGion" parallel to the direction of paddle mcncment. The furnish
was
2~ produced by charging to the tank acidified water, pH 2.7, and solids
composed of 74.5
percent w/w $chuflcr 206 glass fihcrs, average filxr diameter (1.76 llm. 1'.R
percent w/w
'~ Evanite 6 i0 glass fibers, nominal fiber diameter 2.6 t,lm, and I?.$
percent w/w A2()-BC
'h inch glass fibers, nominal fiber diarnetcr 13 t.tm, stirring for about a
minute, charging
to the tank a kraft pulp slurry which had a Canadian frecness of 57cc and a
consistency
"~ of 1.235 percent, and stirring for an additional ? minutes. The composition
in the mixer,
after the pulp addition, contained 73 percent wlw Schullcr 206 glass fibers,
12.5 percent
w/w Evanite 610 glass fibers, 12.~ percent w/w A20-BC-'h inch glees fibers and
3
percent w/w pulp fibrils. The furnish and the pulp were stirred for about two
minutes,
after which the valve was opened so that the water drained through the screen
while the
separator was retained on the screen. The furnish contained enough glass
fibers to
produce a separator having a gramnlage of 30 glm~ at a thickness of 0.1~ mm.
The
separator hand sheet was heated in a drying oven to about 1 SO° for 30
minutes. Two
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s
separator sheets produced as described above were tested and various data,
summarized
below, were collected (the data arc avcragGS of the determinations on the two
sheets).
Frazicr permeability, in the following data and elsewhere herein, is in
Uscc/m' C~ ''t) mm
HZO. The tests, instruments and apparatus used to determine v arious
properties in F.xampie
1 and elsewhere herein arc described in a publication entitled BCllItl3SM
Standard Test
Methcxls, Battery Council Intcrnational~
Grammagc (g/m~) 3~,,7
Thickness, mm (undo a
IQ load of 1t).3d KPa): ().IS
Tensile, MD
(Ncwtons/m): 3f,z
Tensile, CD
(Ncwtons/m): ?75
Elongation. MD
(percent of total): 1.3
Elongation. CD
(percent c~f total):
Port Sizc-first
Z~Q bu(~(~Ic mctluxl, E~m 3()
Frazicr Permeability 9R
Port size-liquid porosimctrv,
Coultcr. ~xm
minimum 5.1
maximum IR.S
mean S 5
"Frazier Permeability" values reported herein were determined using Frazicr
Permeability tester 91A (TnPP! T'rSlOM-RS).
"Wicking", as reported almcc and subscyucntly herein, was determined by the
~Q procedure described in U.S. patent No. 5,'"S,~9R, column 7, lines '?t) and
following, using
water instead of sulfuric acid as there described; the test is known as t)tc
Japanese
Industrial Standard rncthod.
The composition of the Schullcr 2t)6 glass fibers used in Example 1 and in
subsequent Examples var~~ slightly from time to time. Mean values, in percent
w/w,
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calculated from data furnished by Schuller for the period when the examples
were carried
out are given below:
SiO, 65.40 Na,O 16.11
A1.,0~ 2.99 K~O 0.69
Ca0 5.88 B,03 5.31
Mg0 2.79 F~ 1.02
Schuller also indicates that the glass contains Fe~O,, TiO~, ZrO~, Cr,Oz, SrO,
BaO, MnO,
ZnO, Li~O, SO, and Pb in amounts less than 0.1%.
The nominal composition of the Evanite 610 glass fibers used in Example 1 and
in subsequent Examples varies, in percent w/w, within the following ranges:
SiO, 60.0 - 69.0
AI,Oz 3.0 - 6.0
Ca0 5.0 - 7.0
Mg0 2.5 - 4.5
Na,O 8.0
- 12.0
K,O 0.5
- 3.0
B~O~ < 0.02
F, 0.0 - 1.0
Zn0 <0.04
Fe~O~ <0.02
The A20-BC-'/a inch glass fibers used in the procedure described above and in
other
procedures described herein are commercially available from Schuller under the
indicated
designation.
Glass fiber separator sheets according to the invention were produced on a
pilot
plant paper making machine by depositing a furnish on an advancing wire,
through which
water from the furnish drained. The furnish was produced in a mixer from
acidified water,
pH 2.7, and solids composed of Schulier 206 glass fibers, Schuller 210X glass
fibers,
nominal fiber diameter 3.0 um and the same composition as the 206 fibers, and
A20-BC-
1/z inch glass fibers. The furnish was stirred in the mixer for about one
minute, after which
time a kraft pulp slurry which had a Canadian freeness of 57cc and a
consistency of 1.235
percent was added to the furnish in the mixer. The composition in the mixer,
after the
pulp addition, contained about 7 parts by weight of Schuller 206 glass fibers,
about 1 part
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by weight of each of Schuller 210 glass fibers, A20-BC-'h inch glass fibers,
and about
0.6 part by weight of pulp fibrils. The furnish and the pulp were stirred for
about two
minutes, after which time the pulp-containing furnish was charged to the
headbox of the
pilot plant machine. An addition of 0.6 part by weight of pulp fibrils from
red wood pulp
5 that had been beaten to a Canadian_ freeness less than 100 cc was then made
to the
material in the headbox, and the furnish which resulted was flowed onto the
advancing
wire to produce a separator having a grammage of 30 g/m' at a thickness of
0.15 mm.
The separator was ultimately heated in a drying oven to about 150° for
30 minutes. The
separator had a loss on ignition a little over 12 percent w/w, indicating a
total pulp
10 content of about 12 percent w/w. The procedure described in this paragraph
constitutes
the best mode presently contemplated by the inventors with respect to the
production of
battery separator material according to the invention.
Cells according to the invention were made using the separator material
produced
in the pilot plant paper machine as described above, and were subjected to
life testing in
comparison with batteries made using conventional, all glass separators, but
otherwise
identical. Batter's capacity after each cycle, as a percentage of initial
capacity, is set forth
in Table I, below (the control battery test was terminated after 7 cycles):
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Table I
Number of cycles Capacity, percent of initial
According to invention Control
1 113.5 103.6
2 115.6 93.6
3 111.9 76.0
4 109.3 53.4
5 107.4 34.0
G 105.3 25.1
7 103.6 20.9
8 101.7
9 100.0 * *
10 98.6
11 97.2
~5 12 95.5
13 93.7
14 90.1
87.6
1G 86.1
~0 17 80.0
18 74.9
19 74.0
67.3
The data in Table I are presented graphically in Fig. 3, which was computer
generated by
entering the foregoing data for the battery of the invention and for the
control after cycles
1 through 7, but entering zero for the percent of initial capacity after
cycles 8 through 20.
EXAMPLES 2-6
Glass fiber separator hand sheets were also produced from other furnishes
which
contained varying amounts of kraft pulp that had been beaten to a consistency
of 0.9906
percent and a Canadian freeness of 57cc. The furnishes also contained the
previously
identified Schuller 206, 210X and A20-BC-'/z inch glass fibers. The hand
sheets were
produced in a laboratory apparatus by depositing a furnish on a wire or
screen, and
draining the furnish. The apparatus comprised a tank with a screen in the
bottom, a drain
below the screen, a valve which opened and closed the drain, and paddles which
were
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moved back and forth to simulate the movement of a furnish in commercial
papermaking
apparatus and establish a "machine direction" parallel to the direction of
paddle
movement. The furnish and the pulp were stirred for about two minutes, after
which the
valve was opened so that the water drained through the screen while the
separator was
retained on the screen. The furnish that was charged contained enough glass
fibers to
produce a separator having a grammage of 30 g/m'- at a thickness of 0.15 mm.
The
separator hand sheet was heated in a drying oven to about 150° for 30
minutes. The final
compositions, in percent w/w, of representative ones of the furnishes and the
properties
of the hand sheets that were produced are set forth in Table II, below, where,
as in other
tables herein, unless otherwise indicated, tensile strength is in pounds per
inch of width
of the separator (multiply times 0.175 to convert to kilonewtons pcr meter),
elongation is
in percent, stiffness is "Gurley Stiffness" in mg, pore sizes arc in um,
electrical resistance
is in ohms per square inch of the separator, and LOSS 011 lgllltl011 1S 117
percent w/w. The
compositions of the furnishes are given in the following table:
Composition Example Example Example Example Example
of 2 3 ~ 5 6
furnish
210 X 79 77 73 7U 65
A20-BC 'h 10 10 10 10 10
inch fibers
2-00206 10 10 10 10 10
Cellulose 1 3 7 10 15
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Table II
Property Example Example Example Example Example
2 3 :1
grammage, 119.9 121.7 119.3 119.9 119.4
5_ g/m2
Thickness,
mm
(10.34 KPA) 0.765 0.850 0.653 0.620 0.591
(20 KPa) 0.726 0.753 0.644 0.590 0.570
Tensile,
1-00Newtons/m
MD 71.7 135.0 135.7 139.2 149.5
CD 84.7 117.8 108.9 125.4 130.2
Elongation
Percent MD 1.37 2.00 1.96 2.08 2.13
1-55CD 1.83 1.67 1.61 1.70 1.92
Frazier
Permeability65.7 50.2 13.:1 5.9 n.d.
Wicking
seconds/10 83 89 104 153 247
mm
~0 Stiffness,
mg
MD 3800 3900 5200 4300 3200
CD 3100 3500 3900 3500 3000
Pore Size-
first Bubble
25 Method, ,um 16.5 16.0 20.1 21.6 24.0
Electrical 0.002 0.003 0.009 0.011 0.014
Resistance
LOI,% 3.3 52 9.0 12.5 18.1
Pore size-
30 liquid
Porosimetry
Coulter,
,um
Min 5.570 5.386 3.734 2.628 1.697
Max 42.24 42.24 26.07 17.80 12.43
35 Mean 8.875 8.507 5.753 4.425 3.497
In the foregoing table and in subsequent tables the entry "n.d." means not
determined, in
the cases of Examples 6 and 11, because the porosity was too low for a
determination of
Frazier Permeability.
40 Control glass fiber separator hand sheets were produced by the same method
from
a furnish which was composed of 80 percent w/w of Schuller 210X glass fibers,
10
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WO 98/00875 PCT/US97/11579
14
percent w/w of A20-BC-lh inch glass fibers and 10 percent w/w Schuller 206
glass
fibers. The average test results for two control sheets are set forth in Table
III, below:
Table III
Grammage, g/m' 117.1
Thickness, mm
(10.34 KPA) 0.857 g/m'
(?0 KPa) 0.717 g/m'
Tensile, Newtons
per M
MD 10.8
CD 11.0
Elongation, %
MD 0.70
CD 1.21
Frazier Permeability178.4
Wicking 62
seconds/10 mm
Stiffness, mg
MD 980
~0 CD 655
Pore Size-first
bubble Method, ~m 11.0
Pore size-liquid
porosimetry,
~5 Coulter, q.m
Min 6.86
Max 65.97
Mean 12.98
Electrical n.d.
30 Resistance
LOI, % 0.31
Thickness in mm x 1000 of samples of the hand sheets produced as described in
Examples 2 through 6 and of the control sheets was also determined under
various loads,
35 both in an as produced condition and after having been wet with 7 times its
dry weight
of sulfuric acid, specific gravit}~ 1.286. All thicknesses reported herein
were determined
by the method described in U.S. patent No.5,336,27>. The example numbers are
column
headings in Table IV, below, and thicknesses (the values reported are measured
thicknesses in mm x 1000) when the samples were in the as produced condition,
at
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WO 98/00875 PCT/US97/11579
applied loads in KPa indicated in the left column, are set forth under the
identifying
headings:
Table IV
Applied Load,ControlEx. 2 Ex. Ex. 4 Ex. Ex. 6
KPa 3 5
3.79 38 36.5 31 28.5 26
6.06 35 30.5 26 25.5 23
9.51 29.5 27.5 23 23.5 ? 1 19.5
13.71 25.5 25.5 21 22.5 20 18.5
~_0 17.57 22 23.5 20 21.5 19 17.5
23.98 20 22.5 18.5 20 19 17
28.87 19 21.5 17.5 19.5 18 16.5
42.65 16.5 19 16.5 18.5 17 15.5
15 "Rebound" thicknesses in mm x 1000 (after the excess of the load above 3.79-
KPa
was removed from each "as produced" sample) are given in Table V, under
headings
which give the load that was applied, and from which each sample "rebounded";
the
values reported are 1000 x thicknesses in mm at the loads indicated in the
left column of
the table:
Table V
Applied Control Ex.2 Ex.3 Ex.4 Ex.S Ex.6
Load, KPa
6.06 36 33.5 28.5 27.5 24.5 26.5
9.51 33.5 30.5 29 26.5 23.5 25.5
13.71 31.5 29.5 27 25.5 22.5 26
17.57 29.5 28.5 25.5 25.5 22.5 26
23.98 29 27.5 25 25.5 22.5 25
28.87 28 27.5 25 24.5 22 23.5
42.65 27 27 24 24.5 22 23
_30
The
data
in
Tables
1V
and
V
are
presented
graphically
in
computer
generated
Figs.
4
through
9
of
the
drawings,
where
the
loads
are
shown
in
psi,
and
successive
points
along
the
X
axis,
which
are
equally
spaced
from
one
another,
represent
0.55
psi
(3.79KPa},
0.88
psi
(6.06
KPa),
1.38
psi
(9.51
KPa),
1.99
psi
(I3.71
KPa),
2.55
psi
(17.57
KPa),
3.48
psi
(23.98
KPa),
4.19
psi
(28.87
KPa),
and
6.19
psi
(42.65
KPa}.
Accordingly,
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16
Figs. 4 through 9 are skewed in the sense that, for example, a given distance
between the
first and second points represents a change from 0.55 psi (3.79 KPa) to 0.88
psi (G.OG
KPa), while the same distance between the last two points represents a change
from 4.19
psi (28.87 KPa) to 6.19 psi (42.65 KPa). In order to represent the data from
the control
5_ sheets and from Example 2 in a more nearly conventional plot, thickness and
rebound
thickness (in mm x 1000) were calculated by interpolation from the
experimental data for
loads of O.G9 psi (4.75 KPa), 1.19 psi (8.20 KPa), 1.G9 psi (11.64 KPa), 2.19
psi (15.09
KPa), 2.69 psi (18.53 KPa), 3.19 (21.98 KPa), 3.G9 psi (25.4? KPa). 4.G9 psi
(32.31 KPa),
5.19 psi (35.76 KPa), and 5.69 psi (39.20 KPa). These and the experimental
values (in
mm x 1000) at 4.19 psi (28.86 KPa) and at G.19 psi (42.65 KPa) are set forth
in Tables
VI and VII, respectively:
Table VI
Applied Load,Control,Example Control,Example
KPa thickness2, Rebound 2,
thickness Rebound
4.75 3 G.7 34
8.20 31.G 28.G 34.8 32
11.64 28.0 2G.7 32.3 30
15.09 24.3 24.8 30.5 29.G
18.53 22.8 23.8 29.5 28.4
?0 21.98 20.G ~~.8 29.2 X8.4
25.42 20.3 22.7 28.7 X7.5
28.86 30 22.5 28 27.5
32.31 19.2 21.7 27.8 27.4
35.76 18.3 20.8 27.5 27.3
39.20 17.4 20.2 27.3 27.2
42.65 1G.5 19 27 27
The data from Table VI are presented graphically in Figs. 1(i and 17, which
are
computer generated plots using loads in KPa. It will be noted that the curves
of Figs.
16 and 17 are similar in shape to those of the corresponding curves of Figs. 4
and 5,
which is deemed to indicate that valid conclusions can be reached from the
skewed
curves.
Thickness and rebound thickness measurements were also made on the separator
materials of Examples 2 through G and the controls after the materials had
been wet
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17
with sulfuric acid having a specific gravity of 1.286. The applied loads in
KPa are given
in the left hand column of Table VII, below, and thicknesses are set forth
under the
headings which identify the samples; the reported thicknesses are 1000 times
the
measured thicknesses of the separator in mm:
5_ Table VII
Applied ControlEx.2 Ex.3 Ex.4 Ex.S Ex.6
load, KPa
3.79 36 20.5 28 29 27.5 27.5
6.06 31.5 27 26 26 25 24,5
9.51 28.5 24 23 24 22 22.5
13.91 26.5 22.5 21 22.5 20.5 20,5
17.57 24 21.5 20 21.7 19.5 19
23.98 20.5 20.5 19 20 19 17.5
28.87 19 19.5 18 19 18 16.5
42.65 17.5 17.5 16.5 17.5 16.5 15.5
"Rebound" thicknesses (after the excess of the load above 3.79 KPa was
removed from each sample that had been wet with sulfuric acid) are given in
Table
VIII, below, adjacent entries in the left hand column which give the load that
was
applied, and from which each sample "rebounded"; the values reported are 1000
x
measured thicknesses in mm):
Table VIII
Applied ControlEx. Ex. Ex. Ex. Ex.
Ioad,KPa 2 3 ~ 5 6
6.06 32.5 27.5 26.5 27.5 27 25.5
9.51 31 25.5 25.5 26.5 25 24.5
13.91 29 25.5 25 25 25 23.5
17.57 27.5 25.5 25 25 25 23.5
23.98 24.5 24.5 24 25 24.5 23.5
28.87 24 24.5 24 25 24 22.5
42.65 23.5 24.5 24 24.5 24.5 ~~.5
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18
The data from Tables VII and VIII are plotted in Figs. 10 through 15, where
loads are in KPa. The data of Tables IV, V, VII and VIII and Figs. 4-15
indicate that
the separator materials of Examples 2 through 6, above, all have sufficient
resiliency
that they can be compressed between the plates of a lead acid battery, and
that their
major surfaces will be urged against the adjacent plates with sufficient force
for the
battery to perform satisfactorily.
EXAMPLES 7-11
Glass fiber separator hand sheets were also produced by the method described
in Example 1 from other furnishes which contained varying amounts of kraft
pulp that
had been beaten to a consistency of U.990G percent and a Canadian freeness of
57cc,
and were then dipped in a latex, 3 percent w/w solids. The final compositions,
in
percent w/w, of representative ones of the furnishes are set forth in Table
IX, below,
and the properties of separators produced from the furnishes are set forth in
Table X,
below, where thickness of the separator material is in mm:
Table IX
Composition Example Example Example Example Example
of Furnish 7 8 9 10 11
210 X 79 77 73 70 GS
A20-BC 10 10 10 10 1U
''0 1/z inch
fibers
20G 10 10 10 10 10
Cellulose 1 3 7 10 1 S
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19
Table X
Property Example Example Example Example Example
7 8 9 10 11
grammage 121.6 121.9 127.5 123.1 122.7
S g/mz
Thickness,
mm
(10.34 KPa) 0.792 0.778 0.750 0.742 0.603
(20 KPa) 0.760 0.745 0.720 0.698 0.585
Tensile
~_0 Newtons/m
MD 93.0 120.6 139.2 152.3 168.8
CD 80.6 102.0 122.0 139.2 158.5
Elongation,
Percent MD 1.8 2.3 1.9 ?.3 1.9
15 CD 1.5 2.1 2.0 2.1 .0
?
Frazier 8.97 5.08 1.39 0.918 n.d.
Permeabilit~~
Wicking
seconds/10 225 184 253 261 391
mm
0 Stiffness,
mg
MD 2500 3400 4300 4700 4600
CD 2200 2800 3900 3900 3700
Pore Size- 16.8 16.1 19.4 20.5 25,4
First Bubble
?5 Method, ~.m
Pore size- '
liquid
Porosimetrv
Coulter, p,m
30 Min 5.283 4.726 3.427 2.285 1.09?
Max 46.54 40.89 27.52 21.73 11.88
Mean 9.550 7.881 5.839 4.902 2.920
LOI, % 6.7 8.4 12.7 17.1 21.3
35 EXAMPLES 12-16
Still other glass fiber separator hand sheets were produced by the method
described in Example 1 from substantially the furnish of Examples 7-lI which
contained various small amounts of kraft pulp that had been beaten to a
consistency of
1.235 percent and a Canadian freeness of 57cc. The final compositions, in
percent w/w,
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of representative ones of the furnishes are set forth in Table XI, below, and
their
properties are set forth in Table XII, below, where thickness is in mm:
Table XI
CompositionExample Example Example Example Example
5 of Furnish 12 13 14 15 6
1
210 X 77 79 79'/a 79'/z 793/a
A20-BC 10 10 10 1.0 10
1/z inch
fibers
206 10 10 10 10 10
10 Cellulose 3 1 /q 1/2 1/4
3
Table XII
Property Example Example Example Example Example
12 13 14 15 1G
15 grammage 118.4 115.6 117.2 116.4 116.3
g/mz
Thickness,
mm
(10.34 KPa) 0.757 0.751 0.778 0.774 0.797
(20 KPa) 0.662 0.694 0.716 0.703 0.722
20 Tensile
Newtons/m
MD 49.5 25.3 23.8 20.0 18.5
CD 43.8 20.2 20.7 20.0 2.54
Percent
Elongation 8.41 5.75 6.58 6.68 7.82
MD
CD 8.23 6.48 6.06 6.13 8.89
Frazier 129.6 175.2 175.2 186.4 200.8
Permeability
Wicking
seconds/IO 74 76 72 G7 62
mm
Surface area 0.6874 0.6114 0.6603 0.6513 0.7030
Corr. 9.9970 9.9962 9.9991 9.996? 9.9970
Pore size-
liquid
Porosimetry,
Coulter, pm
Min 6.050 5.941 7.050 6.496 7.589
Max 44.71 50.49 62.08 70.13 78.26
Mean 10.65 12.04 12.32 12.59 12.17
LOI 0.46 1.56 1.28 0.89 0.75
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21
Control glass fiber separator hand sheets were produced by the same method
from a furnish which was composed of 80 percent w/w of Schuller 21UX glass
fibers,
percent w/w of A-2,0-BC 1/z inch glass fibers and 10 percent w/w Schuller 206
glass
fibers. The test results, average of two, are set forth in Table XIII, below,
where
5 thickness is in mm:
Table XIII
grammage, g/m' 113.7
Thickness, mm
10 (10.34 KPa) 0.742
(2.0 KPa) 0.600
Tensile
Newtons/m
MD 10.1
CD 11.0
Elongation,
MD 0.96
CD 1.27
Frazier 22.4
~0_ Permeability
Wicking
seconds/10 mm 62
The data concerning Frazier permeability from Table X (Examples 12 through
16) and from Table XI (for the corresponding controls) are presented
graphically in Fig.
l, which is a computer generated plot of Frazier permeability (called CFM on
the
drawing) vs. cellulose content. It will be noted that Fig. 1 has points on the
X axis for
1.25, 1.5, 1.75. ?.0, 2.25, ?.5 and 2.75 percent pulp. To cause the plot to
show these
points, for which there was no experimental data, Frazier permeability was
calculated
for each, of these pulp contents by interpolation between the experimental
values at 1.0
percent and at 3.0 percent. The experimental and calculated data input to
generate Fig.
2 are set forth below:
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22
Percent w/w cellulose ; Frazier Permeability
0.0 ;
o.~s ; ~s.os
0.5
?3.2,5
5_ 0.75
; 21.9
1.0 ; ?1.85
1.25 (Calc) ; ?1.14
1.5 (Caic) ; ?0.44
1.75 (Calc) ; 19.73
2.0 (Calc)
19.03
2.25 (Calc) ; 18.32
?.5 (Calc) ; 17.61
2.75 (Calc) ; 16.91
3.0
; 16.2
The data concerning tensile strength from Table XII and from Table XIII are
presented
graphically in Fig. ?, which is composed of two computer generated plots of
tensile
strength in pounds per inch (machine direction, in one case, and cross
direction in the
other) vs. cellulose content. It will be noted that Fig. 2 has points on the X
axis for
20 1.25, 1.5, 1.75. 2Ø ?.25, 2.5 and 2.75 percent pulp. To cause the plot to
show these
ordinate points, for which there was no experimental data, tensile strength in
both
directions was calculated for each of these pulp contents by interpolation
between the
experimental values at 1.0 percent and at 3.0 percent. The experimental and
calculated
data input to generate Fig. 2 are set forth below:
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23
Percent w/w cellulose ; Tensile, MD (Pounds per inch)
0.0 ; 1.46
0.25 ; 2.685
0.5 ; 2.90
5_ 0.75 ; 2.45 5
1.0 ; 3.63
1.25 (Calc) ; 4.07
1.5 (Calc) ; 4.52
1.75 (Calc) ; 4.96
~0 2.0 (Calc) ; 5.41
?.25 (Calc) ; 5.85
''.5 (Calc) ; 6.29
2.75 (Calc) ; 6.74
3.0 ; 7.18
Percent w/w cellulose ; Tensile, CD (Pounds per inch)
0.0
1.55
0.25 ; 2.54
0.5 ; 2.72
0.75
3.005
1.0 ; 2.93
1.25 (Calc) ; 3.36
1.5 (Calc) ; 3.79
1.75 (Calc) ; 4.22
~5 ?.0 (Calc) '
4.65
2.25 (Calc) ; 5.07
2.5 (Calc) ; 5.50
?.75 (Calc) ; 5.93
3.0 ; 6.36
30 If the calculated data were not plotted, the computer generated plot would
move the
point representing 3.0 percent w/w pulp to the left to the point which
represents 1.25
percent w/w pulp in Fig. 2, so that the curves would rise sharply from tensile
strengths
of 1.93 and 3.63 at 1.0 percent w/w pulp to tensile strengths of 6.36 and 7.10
at 3.0
percent w/w pulp, but the distance along the X axis from 1.0 to 3.0 would be
the same
35 as the distance from 0.75 to 1Ø
EXAMPLES 17-24
Still other glass fiber separator hand sheets were produced by the method
described in Example 1 from furnishes containing 35 parts by weight of 206
glass
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24
fibers, 65 parts by weight of 210 glass fibers and about 1-2 parts by weight
of kraft
pulp that had been beaten to various Canadian freenesses. The Canadian
freeness of
representative ones of the furnishes and various properties of the separators
produced
therefrom are set forth in Table XIV, below, where thickness is in mm. Because
of the
_5 small size of the samples and lack of uniformity of the furnishes, the loss
on ignition
("LOI") of the hand sheets is the best indication of the cellulose content of
the furnish
from which it was produced. A hand sheet containing no cellulose can be
expected to
have a loss on ignition of about '/2%.
Table XIV
Property Example Example Example Example
17 18 19 20
Canadian Freeness 660 548 4?0 225
Grammage 147 143 141 143
g/m'
Thickness, mm
10 KPa 0.96 0.9? 0.88 0.g9
KPa 0.84 0.81 0.82 0.88
50 KPa 0.79 0.70 0.70 0.68
Average total 1.8 2.3 ~.3 1.9
tensile, pounds per
inch
20 Average 2.2 2.4 2.8 2.1
elongation, %
Loss on ignition, 1.6 1.3 ?.0 1.7
~l0
Average Tensile 0.01?? 0.0161 0.()163 0.0133
g/m'
'
'S
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Table XIV (continued)
Property Example Example Example Example
21 ~~ 23 ~4
Canadian Freeness 120 40 30 20
Grammage 143 142 137 146
5_ g/m2
Thickness, mm
10 KPa 0.97 0.91 0.94 0.92
20 KPa 0.84 0.80 0.82 0.82
50 KPa 0.73 0.70 0.70 0.72
10 Average total 2.4 2.5 3.0 4,5
tensile, pounds
per inch
Average 2.2 2.3 2.3 ?.>
elongation, %
Loss on ignition, 1.8 1.5 1.8 ~,6
%n
15 Average Tensile 0.0133 0.0176 0.0219 0.0308
g/m'
EXAMPLES 25-32
Still other glass fiber separator hand sheets were produced by the method
described in Example 1 from furnishes containing 35 parts by weight of 206
glass
fibers, G5 parts by weight of 210 glass fibers and 3-5 parts by weight of
kraft pulp that
had been beaten to various Canadian freenesses. The Canac~;a" fr~PnPCe of
representative ones of the furnishes and various properties of the separators
produced
therefrom are set forth in Table XV, below, where thickness is in mm:
25 Table XV
Property Example Example Example Example
25 ~6 27 28
Canadian Freeness 660 548 420 ~~5
~Grammage 148 144 138 141
g/m'
Av erage total 2.6 3.0 2.7 .8
?
tensile, pounds
per inch
Average 1.9 2.5 3.1 2,2
elongation, ~o
Loss on ignition, 3.5 3.7 3.8 4.0
~n
Average Tensile 0.0176 0.0208 0.0196 0.0199
g/m'
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WO 98/00875 PCT/US97/11579
26
Table XV (continued)
Property Example Example Example Example
29 30 31 32
Canadian Freeness 120 40 30
Grammage 141 140 141 141
m
1
Average total 3.5 3.5 5.1 7,0
tensile, pounds
per inch
Average 1.9 2.0 2.1 2,0
elongation, %
Loss on ignition, 4.5 3.6 3.6 4.1
%
Average Tensile 0.0248 0.0260 0.036'_' 0.0496
g/m'
~5_ EXAMPLES 33-4U
Still other glass fiber separator hand sheets were produced by the method
described in Example 1 from furnishes containing 35 parts by weight of 206
glass
fibers, 65 parts by weight of 210 glass fibers and 9 to 11 parts by weight of
kraft pulp
that had been beaten to various Canadian freeness. The Canadian freeness of
representative ones of the furnishes and various properties of the separators
produced
therefrom are set forth in Table XIV, below, where thickness is in mm:
Table XVI
Property Example Example Example Example
33 34 35 36
Canadian Freeness 660 548 420 225
Grammage 148 146 140 145
g/m~
Average total 2.5 3.8 4.5 5.1
tensile, pounds per
inch
Average 2.1 2.1 2.1 2,0
~0_ elongation,
Loss on ignition, 11.3 11.5 8.7 10.0
%
Average Tensile 0.0169 0.0261 0.0319 0.0364
g/m'
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27
Table XVI (continued)
Property Example Example Example Example
37 38 39 40
Canadian Freeness 120 40 3p
Grammage 138 144 140 150
5_ g/m'
Average total 6.9 7.8 9.0 13.3
tensile, pounds
per inch
Average 2.0 2.3 1.8 ?.?
elongation, %
Loss on ignition, 12.0 10.~ 11.5 11.0
%
Average Tensile 0.0500 0.0542 0.0643 0.0887
g/m'
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28
As has been indicated above, a remarkable increase in tensile strength is
achieved when separator material according to the invention is produced using
pulp that
has been beaten or refined to a Canadian freeness not greater than about 120
cc. This
increase is illustrated by the data of Examples 17 through 40 concerning
tensile strength
5_ of separator materials according to the instant invention produced from
furnishes
containing varying amounts of wood pulp which had been refined to several
different
Canadian freenesses. The data concerning average tensile strength in g/m' vs.
Canadian
freeness are presented graphically in charts A, B and C, below. Chart A is a
plot of the
indicated data from Examples 17 through 24; Chart B is a plot of the indicated
data
from Examples 25 through 32; and Chart C is a plot of the indicated data from
Examples 33 through 40.
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WO 98/00875 PCT/US97/11579
29
Chart A
Chart B
Chart C
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It has been found that the separator material produced as described in each of
the foregoing Examples can be charged to conventional papermaking apparatus,
and
"repulped", either as the sole source for glass fibers and cellulose fibrils
or
supplemented with additional glass fibers and cellulose fibrils to produce a
furnish
5 which can be deposited on the moving wire of paper making apparatus as
described
above to produce separator material. As a consequence, there is no need for
any of the
separator material according to the instant invention to be scrapped; instead,
it can be
recycled. Further, separator material according to the instant invention has
improved
puncture strength than otherwise identical separator material which does not
contain
10 cellulose fibrils; as a consequence, increased yields of acceptable lead
acid batteries
having expanded metal or continuous cast grids can be achieved.
As has been explained above, separator material made from first fibers which
impart to the sheet an absorbency greater than 90~~n and second fibers which
impart to
the sheet an absorbency less than 80% wherein the first and second fibers are
present
15 in such proportions that the sheet has an absorbency of from 75 to 95%,
when saturated
with electrolyte, still has unfilled voids so that gas can transfer from plate
to plate for
recombination. Such separator material can be produced according to the
instant
invention by adding to a slurry COlltallllllg, in suitable proportions, first
fibers which
impart to the sheet an absorbency greater than 90% and second fibers which
impart to
20 the sheet an absorbency less than 80%, from 0.2 percent w/w to 20 percent
w/w of a
slurry of cellulose fibrils having a Canadian frccness sufficiently low that a
separator
material produced from the resulting slurry has a tensile strength greater
than an
otherwise identical separator where glass fibers having an average diameter
greater than
1 ~.m replace the cellulose fibrils. Preferably, the fibers which impart to
the sheet an
25 absorbency less than 80% include both relatively coarse glass fibers and
hydrophobic
organic fibers. Polyethylene, polypropylene, acrylic and polyester fibers are
examples
of preferred hydrophobic organic fibers.
A preferred separator according to the invention having an absorbency (as
defined in the above identified Badger patent, of from 75 to 95% which, when
saturated
with electrolyte, still has unfilled voids so that gas can transfer from plate
to plate for
recombination contains 33.6 parts by weight Schuller 206 glass fibers or an
equivalent,
50.4 parts by weight Schuller 210X fibers or an equivalent, 11 parts by weight
Schuller
A20-BC'/a inch glass fibers or equivalent, and 5 parts by weight of
polyethylene fibers,
and, in addition, from 0.~ percent w/w to ?0 percent w/w of cellulose fibrils
from a
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31
slurry having a Canadian freeness sufficiently low that the separator material
has a
tensile strength greater than an otherwise identical separator where glass
fibers having
an average diameter greater than 1 p.m replace the cellulose fibrils.
it will be appreciated that various changes and modifications can be made from
the specific details of the invention as described above without departing
from the spirit
and scope thereof as defined in the attached claims.
