Note: Descriptions are shown in the official language in which they were submitted.
--1--
escriytion
_attery Separator for Lead-Acid Ty_e Bat-teries
Technical Field
.
~he present invention relates to battery separators and is
more particularly concerned with a new and improved battery
separator material especially designed for use in maintenance-
free automotive batteries of the lead-acid type.
Heretofore, battery separators for use in lead-acid storage
batteries have consisted of thin fibrous sheets, such as papers, of
electrically insulating porous material adapted for prolonged immer-
sion in the acidic electrolyte between adjacent plates of the
battery. ~bre recently maintenance-free batteries have employed
noncellulosic, nonwoven fibrous webs as the electrolyte absorbing
and retaining structure.
m e nonwoven materials used in maintenan oe-free batteries have
been comprised predominately of glass and~or synthetic FibersO The
electrolyte absorbing and retaining separators of such batteries
typically absorb the liquid acid electrolyte and distribute it
throughout the separator to such an extent that substantially all
of the electrolyte is absorbed within the pores of the separator and
only a thin film of electrolyte is present on the plates of the
battery. The highly retentive and porous flexible separators are
typically placed between the plates of opposite polarity which
are capable of being stacked and confined within a container
exhibiting a variety of configurations and shapes. Such separators
~`
. .
.
:
-2--
retain the electrolyte in intimate proximity to the plates regard~
less of the position of the cells.
In the maintenanoe-free battery it is important to control
the amDunt of electrolyte placed in the cell~ There must be
enou~h so that the hydrogen and sulphate ions together with water
are sufficient to support the electrochemical reaction, but there
should be little or no exoess or free electrolyte. Substantially
all of the electrolyte should be retained within the interstices
of the sep æator structure. Thus, the electrolyte content of the
battery is in a more or less starved condition. It is important
to maintain a starved electrolyte condition in order to max~mize
or enhance the reccmbination at the negative plate of oxygen formr
ed at the positive plate. In this way gas evolution is reduced
and improved electrical performance is obtained over a prolonged
period.
A glass sep æ ator material made from microfiber diameter,
short staple, glass fibers for use in a st æved electrolyte system
is described in GB Patent 1,364,283, In that patent the sheets of
glass fibre material have a high surfaoe area with correspondingly
small fibre diam~ter and are capable of retaining the electrolyt~
within the separator itself. In order to obtain maximum electro-
lyte retention, the separator uses microfine fiber filaments wi-th
high surfaoe area per unit of weight. The diameter of the fibers
used in these highly flexible materials is in the range of 0.2 to
10 microns and they have a surface area of approximately 0.1 - 20
square meters per gram of silica. m is very high surfaoe area,
together with the action by the sulfuric acid of the electrolyte
- ' . ' .' : :
. .
--3--
on the glass, is said to result in a separator having a very high
volume retentivity of electrolyte per ~it volume of separator.
Examples of synthetic fiber battery separators may be found
in GB Patent Applications 2,017,184A and 2,020,086A. In the
forNer application, the separators consisted of 70 percent synthet-
ic fiber and 30 percent wood fiber, while in ~he latter application
a mixture of polyolefin fibers of different coarseness are used,
either alone or together with an inert filler.
In accordance with the present invention it has been found
that superior acid retention can be achieved together with compar-
able electrical properties in a more economical manner. This is
accomplished by forming a battery separator from a non oellulosic
nonwoven fibrous web material having an acicular mineral material
as a significant ccmponent of the fibrous web~ m e separator
materi~l also contains microfine glass fibers, perferably in
amounts almost equal to the amounts of the acicular mineral mater-
ial and utilizes substantially less than 25 percent by weight of a
synthetic binder fiber. Advantageously this material exhibits
equivalent or superior performan oe characteristics relative to
p Aor separators used in maintenan oe-free batteries yet is of
significantly lower cost.
Other advantages and feàtures will be in part obvious and in
part pointed out more in detail hereinafter~
These and related advantages are obtained by providing an
electrolyte absorbing and retaining battery separat~r for lead-
acid ~atteries of the starved electrolyte type wherein the separat-
or is a noncellulosic nonw~ven fibrous web material comprised of
~ .~
--4--
(1) 10-90 percent by weight of an acicular mineral material ex-
hibiting a specific gravity substantially greater than 2.46 g/cc,
(2) electrolyte resistant microfine fibers, such as glass fibers,
having an average fiker diame-ter of less than 10 microns, and
(3) less than 25 percent by weight of a synthetic binder fiber.
The nonwoven web material exhibits a void volume greater than about
85 percent, an electrolyte absorption of at least about 0.06 g/sq. cm.
and an acid retention of at least about 35 percent of said absorption.
A better understanding of the invention will be obtained from
the follcwing detailed description wherein the article of manufac-
ture possesses the features/ properties and relation of elements
described and exemplified herein.
Description of a Preferred Emb diment
As mentioned, battery separators utilized heretofore in mam-
tenance-free lead-acid batteries have been made almost entirely
from microglass or synthetic fibers. In accordance with the
present invention from 10 to 90 percent by weight of the fiber
content of the battery separator is comprised of a nonmetallic
acicular mineral material that is substantially less expensive
than the microglass fibers yet provides comparable, and even
superior, results with respect to the electrolyte absorption and
retention characteristics of the battery separator material. The
microglass fibers used heretofore also are used in the battery
separator of the present invention to~èther with a minor amount of
synthetic binder fiber
In view of the acidic environment of the battery separator
during use, it is preferred that the sheet material be non oellul-
--5--losic and not subject to attack by that environment~ Consequently,
one of the preferred major fiber components of the sheet material
is the inorganic fiber used heretofore. Although glass fibers æe
preferred, other fibers that are resistant to attack by the acid
used as the electrolyt , e.g., sulfuric acid, also may be employed.
For example, typical inorganic fibrous materials such as quartz,
acid resistant ceramic fibers, and the like may be used, with the
preferred fibers being borosilicate glass fibers.
Generally, the inorganic fibers utilized æe of extremely
fine diameter, that is, they exhibit a diameter of less than 15
microns and preferably have a diameter on the order of 0~1-10
microns with best results obtained in the range of 0~5-6.0 microns.
Further, since the fibrous web material is produced by a wet papermaking
process, it is preferable that the fikers be of a paper-
making length and capable of being readily dispersable in water to
form a dilute fiber slurry or furnish usable in a papermaking
operation. As will be appreciated fibers of different diameter
and length may be combined within a single web material and com-
binations of different fibers also may be used with good results.
As mentioned it is a feature of the present invention that up
to about 90 percent by weight of the total fiber content of the
sheet material is an acicular mineral material exhibiting a specif-
ic gravity substantially greater than that of the bnrosilicate
glass normally used in the manufacture of battery separators
Such glass typically has a specific gravity of 2,46g/cc. Ihe
preferred mineral is the naturally occurring material known as
wollastonite. This material is a nonmetallic calcium metasilicate
that typically ~xhibits a very fine diameter size and a length to
¢3~
--6--
diameter ratio in the range of from 3:1 to 20:1~ It has an
acicular crystalline appearanoe , that is, it is of needle shape,
long, slender, and usually pointed at its ends. It ~as a
specific gravity of about 2.9 g/cc, well above the 2.46 value for glass.
It exhibits a fiber diameter range of 0.1 to 5.5 microns and an
average fiber length in the range of 0.3 to 45 microns with a
surface area of approximately 6.3 m2/g.
The preferred acicular material has a length to diameter
ratio at the upper end of t~e aforementioned range, i.e., in the
range of a~out 10:1 to 20:1 and may be used as mined and separated
or may be treated with surface modifyina material to enhan oe its
water dispersibility. One of the benefits of this material is
that it can be obtained in a relatively pure form as a white,
nonmetallic, highly uniform crystalline material. It exhibits
exoe llent dielectric properties and exoeptional resistance to
moisture absorption as well as resistance to attack by acids such
as those used as the electrolyte in lead-acid batteries. A
oommercially available wollastonite found to give good results is
the material sold under the trademark "Nyad" by Interpace Corp.
The attrition-milled grade of this material having a typical aspect
ratio of 15:1 to 20:1 is preferred.
As mentioned, the acicular calcium metasilicate is used in
amounts of from about 10 to 90 percent by weight of the total fiber
content and preferably is employed within the range of 40 to 60
percent by ~7eight with the preferred composition heing approximately
50 percent. As can be appreciated many facto~s-must be considered
-7-
in determining the appropriate amount of the acicular mineral
material From a commercial standpoint is has been determined
that the more economically desirable calcium metasilicate can be
used without sacrifice in ~he necessary physical properties of
the battery separator at levels of at least 40 to 60 percent by
weight. When levels greater than 60 percent are used, satisfact-
ory results are obtained but the performan oe level of the battery
separator drops as the amount of glass fiber is reduoed and re-
placed with the crystalline calcium metasilicate. Below 40
percent, the economic advantage of the metasilicate over the micro-
glass fibers is lessened without a corresponding improvement in the
absorption characteristics of the separator material.
In a similar manner, it is necessary to consider the propert-
ies of the separator material at various binder levels. Since the
binder fiber provides the web material with oertain strength
characteristics but at the same time tends to reduce the electro-
lyte absorption character of the battery separator material, it is
necessary to determine the optimum amount of binder fiber and
thereby balance the degree of absorption loss against the amount
of strength necessary for the sheet material. Additionally, as
will be appreciated, the hydrophobic nature of the binder fiber
tends to reduce the wett~bility of the fibrous sheet material and
correspondingly decrease the absorption characteristics of that
material. Therefore, it is preferred that the lowest possible
amount of synthetic binder fib~r be used in order to achieve the
desired strength characteristics. In this connection, it has been
found that less than 25 percent binder should be used in the fiber
.
.. . .
furnish. Although the all-glass sheets used heretofore as battery
separators have incorporated binders that were applied as dilute
solutions after the web material was formed, it is perferred, in
accordance with the present invention, to provide the hinder in
the form of fibers which constitute significantly less than 25
percent of the total fiber content of the sheet material~ m e
binder fibers typically constitute up to about 15 peroent of the
total fiber content and as little as about 2 per oent by weight
with preferred amounts keing in the range of abou~ 5 to 10 percent
by weight.
As mPntioned, the binder used for the battery separator web
material of the present mvention is preferably in the form of
binder fibers that can be disbursed with the glass fibers prior to
deposition on a paper-forming wire. In this way it is possible to
achieve exoellent random distribution of the fibers throughout the
sheet material. m e binder fibers found particularly advantageous
in this connection are the ployolefin fibers of high molecular
weight and low melt index. These ibers are described in greater
detail in British patent specification No. 1,386,983. As mentioned
in that patent, the essential characteristics of the polyolefin
fibers which distinguishes them frcm conventional fibers is their
surface area of greater than one square meter per gram and their
gxoss morphology, that is, their microfibrillar structure similar
to wood pulp, comprising fibrils which in turn are made up of
microfibrils. In general, the fibrous polyolefin fibers are such
that the polymer cannot be processed into smooth rod-like fibers
by the conventional melt spinning technique. These high molecular
weight polymeric materials have a melt index of less than about
- 1~8t~99
g
0.5 and are not adaptable to conventio.nal processing equipment
due to their pcor flcwability charac-teristics under pressure~
These materials preferably have a melt index belcw 0.1 and an
average molecular ~eight greater than ~00,000. In general, the
polyolefin material should have a viscosity average molecular
weight of at least 40,000 and preferably greater than 500,000.
The binder fihers may be formed under conditions of sheer
stress in an apparatus such as a disc refiner. The resultant
fikers have a typical size and shape co~,parable to the size and
shape of wood fibers and are commonly referred to as "synthetic
wcod pulp~" mey have an average length of about 1 millimeter,
although variations in the manner of their manufacture can result
in lengths up to 4 millimeters and more. Of course, shorter fiber
lengths are also produced with the loh7er limit of the fiber length
being about 0.025 millimeters, ~7ith fibers of the 0.1 to 0.2
millimeters being more commonly observed as the shortest fibers.
Most of the fibers have a length of about 0.2 to 3 millimeters.
These materials have a structure which ccmprises mechanically
inter-entangled bundles of fibrils and macro-fibrils,
the macrofibrils generally having a width in the
range of 1 to 20 microns. In the case of polyethylene,
polypropylene and comb.inations thereof, the polym~ric material
exhibits an average molecular we.ight between 500,000 and
20,000,000 and a surface area in excess of 1 square meter per
gram up to 100 square meters per gram and generally greater
than 25 square meters per gram.
~: . ' , ' ' '
-9a-
Other synthetic thermDplastic :fibers that could be used for
the ~anufacture of the separator according to the present invention
include polyamides such as nylon 6.6 and nylon 6 and polyesterS
such as polyethylene terephthalate as well as the polyolefins
mentioned hereinbefore, including co-polymers and mixtures thereof.
Ihe preferred fibers have a diameter of S to 30 microns and a
length of 1 to 2 microns, although the in~lvidual fibrils are
. ~ ,
9~
-
~10-
present in various sizes and various specific surfaces, the shape
and size distribution not being unlike that of refined wood pulp.
The sheet material of the present invention generally is made
in accordanoe with ccnventional papermaking techniques and pre-
ferably takes the form of a nonwoven structure wherein the binderfibers inter-entangle with the nonbindRr fibers and provide suf-
ficient structural integrity through simple physical interaction
to permit handling of the web material despite a binder fiber
content as low as 2-5 percent. As is well known, all of the fibers
are mixed and thoroughly disbursed in an aqueous medium, frequently
at reduched pH levels by means of a paper mill beater or other
mixing devices. The resultant mixture of fiber furnish is then
oonveyed to the headbox of a papermaking machine where typically
it is further diluted and fed onto the continuous fiber accumwl-
ating paper-forming wire, such as a Fourdrinier wire. Where pH
oontrol is required for dispersion of the inorganic or glass
fibers, this can be achieved either during the mixing operation or
as the fiber furnish is fed to the headbox of the papermaking mach-
ine~ Generally, when handling inorganic fibers, the pH control is
significant and is adjusted to a neutral of acidic condition prior
to the slurry being fed to the headbox.
Although conventional Fourdrinier, cylinder type or other
oommercially available papermaking machines may ke employed, the
battery separator web material of the present invention is most
desirably formed in a papermaking machine utilizing an inclined
wire sin oe more dilute dispersions may be used and greater uni-
formity with sheet structure can be achieved. In such inclined
wire papermaking machines the inorganic fiber dispersion is
,
generally maintained at a con oentration of about 1 percent by
weight and preferably at about 0.1 to 0.3 percent by weight.
Higher concentrations or consistencies may, of course, be applied
on cylinder machines and conventional Fourdrinier machines so
long as the resultant no~woven web material will exhibit the
requisite physical characteristics adapting it for use as a battery
separator. A typical exa~ple of the inclined wire papermaking
machine can be found in U.S. patent No. 2,045,095 issued to F~ H.
Osborne on June 23, 1936. Nonwoven web materials *ormed on such
a machine generally exhibit a desirable three-dimensional network
or conf guration with only slight orientation in the machine
direction .
The fibrous web material formed in accordance with the present
invention is typically dried in a conventional manner and subsequent-
ly subjected to temperatures of about 265F and higher so that thebinder fibers approach and preferably exceed their fusion temper-
ature thereby imparting greater strength characteristics without
interfering with the porosity of the web material~ As will be
appreciated, the melting point of the binder fiber will pe~nit the
web material to be dried immediately after formation without
disadvantageously melting or causing binder buildup on the drier
cans of the papermaking machine. The fihrilliform structure of the
binder facilitates rapid melting or fusing and at the same time
promotes binder adherence to a greater numker of individual glass
and wollastonite fibers. m us, as the sheet material is subjected
to the elevated fusion temperature for a brief period of time, the
binder particles fuse and flow on~o the adjacent fibers in a
substantially complete fashion so as to eli~Lnate the fiber
-12-
structure of the binder. The binder material forms an extremely
thin coating, predominately at the cross-over points of the re-
maining fibers resulting in an effective fiker diameter of only
slightly greater than the diameter of the original fibers them-
selves. As will be appreciated, some small globs of binder willbe present at the cross-over or connecting points of the individual
inorganic fibers, but in most instances, even these melted and
resolidified portions are no larger than the diameter of the fibers
constituting the bulk of the sheet material. As will be appreciated,
this morphology change of the binder assists in retaining the poro-
sity of the fibrous web material while substantially enhancing its
tensile strength.
The resultant nonwoven separator web material of the present
invention provides improved electrolyte absorption and retentivity
which can be attributed at least in part to the high specific
gravity of the acicular mineral material relative to the specific
gravity of borosilicate glass normally used in the manufacture of
nonwoven battery separators. As mentioned, the specific gravity
of the acicular crystalline material is about 2.9 g/cc and the
average surface area of that material is about 6~3 m /g as
contrasted with the surface area of the borosilicate glass of about
3.1 m /g. mese characteristics result in a substantially smaller
average pore size in the web material and a substantially larger
number of pores thereby providing a greater surfaoe area within
the fibrous web material. m ese characteristics, in turn, contri-
hute to the Lmproved absorption characteristics of the web
material.
There is also a relationship between the void volume of the
-13-
material and the specific gravity of the fibers. This can be
found in the definition of void volume as set forth in the
follcwing equation:
V = 100 rl - W
L T(S)~
where V is void volume expressed as a percentage, W is the basis
weight of the sheet material, T is the thickness, and S is the
specific gravity of the fibers. In accordan oe with the present
invention, the utilization of a material which exhibits a sub-
stantially higher specific gravity results in a higher void volume
and therefore improved absorption characteristics. The void volume,
in reality, is a statement of the relationship between the apparent
density of the material and the actual density of the fibers used
to make the material expressed as a peroe ntage. In this connection,
the void volume of the web material is well above the 85 percent
level and is typically at or about 90 percent.
The absorption level of the nonw~ven web material prDduced
in accordance with the present invention on a weight basis is
approximately ten fold and more that of the material itself in a
dry condition. Absorption levels of about 0.06 g/sq. cm. are
typical with the level seldom dropping below 0.045 g/sq. cm. and
extending to and above 0.08 g/sq.cm.
In order to determine the absorption characteristics of the
nonwoven web materials the follcwing test procedure is utilized
as a screening test. In this prodedure, a small sample of the
battery separator material of known dimensional size is weighed in
its dry condition and then is allcwed to ahsorb a standardized
sulfuric acid solution for a period of 24 hours. me standard
~ ' ~
-14-
acid solution is a 43 percent by weight sulfuric acid solution
having a specific gîavity of 1.335. Although absorption is
essentially instantaneous, the 24 hour absorption period is used
to allow for any deterioration or breakdown of the material in the
acid and pro~ide a stabilizing effect. After the 24 hour acid
absorption period, the saturated sample of battery separator
material is weighed to determine the amDunt of acid absorbed by the
nonwoven web. As mentioned, the sheet material of the present
invention absorbs about ten times and more its own weight.
To deter~ine the degree of electrolyte retention, the
saturated sample ob~ained as mentioned a~ove is then lightly blot~
ted on one side with a single dry piece of a battery separator
made fro~ glass fibers only and the hlotted sample is reweighed.
The retention values may be reported as the amDunt of acid remaining
in the sheet material together with the amDunt originally absorbed,
or as a peroentage of the amount oA gi~ally absorbed. In accord-
ance with the present invention, it is preferred that the acid
retention level as detenmined by this test proce~ure be at least
35 to 40 percent and preferably 50 percent or more of the absorb-
tion level at saturation.
It is also desirable that the acid be absorbed within thesheet material as rapidly as possible and that the acid be capable
of saturating the entire separator. Ps will be appreciated, the
high surface area of the battery se~arator material of the present
invention permits extremely rapid saturation of the nonwoven mat-
erial by the acid electrolyte. Additionally~ the very small pore
size provides for improved retention of the absorbed liquid, there-
by providing low resist~n oe to the flow of the electrolyte while
.
-15~
at the same time providing improved or enhanced inhibition to the
passage or migration of fine active materials formed at one elec-
trode and flowing toward the opposite electrode
d~lring use. Further, the electrical resistivity of the
material is very low. A typical average vdlue is about 1.2 milli-
ohms/sq.cm. with the maximum value being 3.0 milli-ohms/sq.cm. and
many readings being less than the indicated typical average value.
me following specific examples are given in order that the
effectiveness of the present invention may be more fully under-
stood. mese examples are set forth for the purpose of illustration
only and are not intended in any way to limit the practi oe of the
invention. Unless otherwise specified, all parts are given by
weight.
EX~IE C~E
Using a commercial papermaking machine, a nonwoven battery
separator material was made in accordance with the present invent-
ion. About 141 p~unds of wet synthetic pulp polyolefin fibers
(56~ pounds on a dry weigh~ ba~is) ~sold under the trademark "PULPEX
E" were added to a beater containing 1800 gallons of water heated
to a temperature of 80F. me fiber dispersion was brushed for 20
minutes and 62 pounds of Code 106 glass fibers having a fiber dia-
meter of approximately 0.5 - 0.75 microns were added to the beater
together with 62 pound~s of ~ inch long, chopped 6 micron diameter
glass rovings (Grade DE) and 195 pounds of the acicular calcium
metasilicate known as wollastonite (Attrition-millèd grade, sold
under the trademark "Nyad-G"). The slurry was defibered for 8
minutes and an additional 600 gallons of water were added thereto~
The fiber furnish was mixed further and fed to the headbax of
an inclined wire paperm~king machine where it was deposited on the
:
-16-
the paper-forming wire at a sufficient concentration to provide
a fibrous web having a basis weight of about ao g/m2 The
machine was run at a speed of about 120 feet per m m ute and the
nonwoven material that was produoe d was dried on can driers heated
to a te~perature of akout 300 F. - 325 F.
The resultant web material exhibited a basis weight of 81.42
g/m2, a thickness of 11.0 mils, and a void volume of 90 percent.
A mercury intrusion analysis was conducted both on this material
and on a commercial all-glass fiber battery separator material
hereinafter referred to as the "control material". The analysis
showed that the material of the present invention exhibited a
larger total pore area and total pore volume and a smaller average
pore diameter than the control material. The total pore volume and
total pore area were 3.0728 cc/g and 1.5504 m2/g respectively,
for the web material of the presen~ inventiGn as compared with
values of 2.9468 cc/g ar.a 0.8354 m2/g for the control
material. me average pore diameters for the respective materials
were measured as 7.9278 microns and 14.1101 microns.
m e web material produced in accordance with this example was
~also tested or electrolyte absorption and retention using the
screening test descriked heretofore. Circular samples of the web
material were cut to a size having a diameter of 6.85 cm. Each
sample was weighed and plaoe d into a solution of 43 percent by
weight sulfuric acid having a specific gravity of 1.335 g/cc. It
was visually observed that the sa~ples exhibited verv rapid wett-
ability. me samples were covered and allowed to remain in the
acid for 24 hours. Each sample was removed from the acid, allcwed
to drain for 5 - 10 seconds and then weighed on a preweighed dish
to determine the amount of electrolyte absorbed. The a~erage
absorption value for four samples of the material of this example
; .
' ~. ' ' ' :
6~
-17-
was 0.0531 g/sq.cmu
The saturated samples were lightly blotted by placing one
side on an all-glass com~ercial grade separator material such as
the control material for 5 - 10 seconds. me blotted samples
were reweighed to detennine the percent of electrolyte retention~
The average retention value was found to be 61 percent. The
retention value for commercial separators using all-glass fibers is
between about 56 and 60 percent.
EXPMPLE TW~
Battery separator material was made in the form of continuous
webs using the procedure and apparatus of Exa~ple One. The fiber
composition ~as changed by reducing the snythetic binder fiber to
a 5 percent level and slightly adjusting the remaining co~ponents.
The properties of the resultant material from this exa~ple are
compared with those of the material from Example One and the control
material in Table I.
TABIE I
Example Exa~ple
Fiber Content (%) Control 1 2
. . ~ , , _
Calcium metasilicate - 52 50
Synthetic pulp (Pulpex E) - 15 5
Code 106 glass fi~er - 1~.5 22~5
DE glass rovings - 16.5 22.5
t~" length)
~ ~g/sq.m) 60 81 95
Thickness (mils) 11.8 11 12.7
Void Volume l%) 91 90 90
-
Avg. Tensile (g/25mm) 700 11~8 1070
.
c~
-18-
TABLE I
Exa~ple Example
Fiber Content (~
wi tro~
Absorption (g/sq. cm) .0728 0531 .0742
.
Retention (%) 60 61 70
EXAMPLE THRæE
Hand sheets were prepared from a fiber furnish identical to
that used in Example Two. The fiber slurry was prepared in sub-
stantially the same m~nner as in Example One. Aftèr mixing the
entire furnish, hand sheets were made and the properties thereof
measured. ~he average values for the physical praperties of the
hand sheets are 6et forth in Table II, which also includes, for
comparative purposes, the data associated with an all-glass
fiber control material~
EXAMPIE EOUR
The procedure of Example Three was repeated exoept that the
amount of synthetic pulp fiber was increased to 10 percent and the
amount of glass fiber was reduced so that the fiber furnish con-
tained 20 percent of each type of glass fiber. Hand sheets were
prepared as in Example Three and the physical data relative thereto
is set forth in Table II.
ExpMæLE FIVE
m e procedure of Example Three was repeated agam except that~
the amount of synthetic fiber was increased to 10 percent and the
amount of acicular calcium metasilicate was reduced to 45 percent.
Hand sheets ~7ere prepared and the physical data relating to this
material is set forth in Table II.
- -- - ~ , :
-- ' ' ' : '
. , : .
~i8~9
--19--
TABLE II
Fiber content (%? Control EX. 3 Ex o 4 Ex~ 5
Calcium metasilicate - 50 50 45
Synthetic pulp 5 10 lO
Code 106 glass - 22.5 20 22.5
DE glass rovings ~" - 22.5 20 22.5
Basis Weight (g/m2) 61 72 71 76
m ickness (mils) 12.05 10.2 9.5 9.9
Absor~tion (g/sq.cm.) 0.0610 0.0800 0.0612 0.0736
(corrected to lO mils)
Retention (%) 57 59 56 56
EXAMPLE SIX
In this example, the procedure of Exa~iple Three was follcwed
but the amount of acicular calcium metasilicate fiber was varied
15 from lO percent to 90 percent using lO percent synthetic pulp
fiber in all instances. Hand sheets were prepared from the
different fiker furnishes and the form~lations and physical
properties relative thereto are set forth in Table III.
TAEiLE III
Fiber Conte~t (%)
Calcium metasilicate lO.0 25.0 75.0 90.0
Synthetic fiber (Pulpex E) 10.0 10.0 10.0 10.0
Oode 106 glass 40.0 32.5 7.5 0
DE glass 40~0 32.5 7.5 0
Basis Weight (g/m ) 56 63 81 100
Thickness (nils) 9. 68 9.98 9.45 10.18
-20-
(g/sq.om.) 0.0650 0.0659 0.0506 0.0506
(corrected to 10 mils)
Retention (~) 48 52 49 60
.
As will be apparent to persons skilled in the artl various
modifications, adaptations, and variations of the foreg~ing
specific disclosure can be made without departing from the teachings
of the present invention.
