CA1258690A - Battery separator - Google Patents
Battery separatorInfo
- Publication number
- CA1258690A CA1258690A CA000494463A CA494463A CA1258690A CA 1258690 A CA1258690 A CA 1258690A CA 000494463 A CA000494463 A CA 000494463A CA 494463 A CA494463 A CA 494463A CA 1258690 A CA1258690 A CA 1258690A
- Authority
- CA
- Canada
- Prior art keywords
- siliceous
- filler
- hollow spherical
- siliceous filler
- polymeric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/429—Natural polymers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Silicon Compounds (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Microporous polymeric battery separator, e.g., rubber separa-tors, exhibit reduced electrical resistance when reinforced with a sili-ceous filler composed of agglomerates of essentially hollow spherical precipitated siliceous particles. The siliceous filler is characterized by a surface area of between about 50 and 250 square meters per gram, a predominant hollow spherical unit particle size of between about 0.005 and about 5.0 microns and an oil absorption of from about 150 to 300 grams per hundred grams of siliceous filler. The hollow spherical precip-itated siliceous filler can be prepared by precipitating siliceous pig-ment onto finely divided water insoluble inorganic salt, e.g., calcium carbonate, and subsequently removing the insoluble inorganic salt, e.g., by leaching with an acid such as hydrochloric acid.
Microporous polymeric battery separator, e.g., rubber separa-tors, exhibit reduced electrical resistance when reinforced with a sili-ceous filler composed of agglomerates of essentially hollow spherical precipitated siliceous particles. The siliceous filler is characterized by a surface area of between about 50 and 250 square meters per gram, a predominant hollow spherical unit particle size of between about 0.005 and about 5.0 microns and an oil absorption of from about 150 to 300 grams per hundred grams of siliceous filler. The hollow spherical precip-itated siliceous filler can be prepared by precipitating siliceous pig-ment onto finely divided water insoluble inorganic salt, e.g., calcium carbonate, and subsequently removing the insoluble inorganic salt, e.g., by leaching with an acid such as hydrochloric acid.
Description
6~C~
BATTERY SEPARATOR
Description of the Inventlon The present invention is dlrec~ed to a siliceous filler-contain-lng battery separator. In commonly used electrlc storage batteries, such as the well-known 12-volt battery employed in automobiles, separators are placed between bat~ery plates of opposite polarity to prevent the two plates from touching each other and causing an electrical short. The separator is typically a microporous article fabrlcated from a polymeric material, e.g., natural or synthetic rubber, or a polyolefin. The separa-tor may ha~e a backing material of, for example, a non-woven web. The pore size of the microporous separator should be as small as possible since this reduces the danger of active materials being forced through or growing through the separator, thereby causing an electrical short.
The separator should also have a low electrical resistance in order to maximize the power output from the battery. Lower electrical resistance can be obtained by reducing the overall thickness of the sepa rator, e.g., the thickness of the backing material; however~ thinner sepa-rators are more subject to corrosion and other physical factors affecting the service life of the separator.
Certain siliceous fillers have been used to prepare mlcroporous battery separators. See, for example, U.S. Patent 2,302,832, which describes the use of a silica hydrogel in a rubber binder, U.S. Patent 3,351,495, which describes synthetic and natural zeolites, precipltated metal silicates, such ~s calcium silicate, and silica gels as the inor-ganic filler and extender for separators of high molecular weight poly-olefins, and U.S. Patents 3,696,061, 4,226,926, and 49237,083, which describe the use of finely di~ided, precipitated amorphous s-llica, such as E1i-Sil~ 233 siliceous pigment, in microporous battery separators.
Typlcally, amorphous precipitated slllca plgment is used to introduce porosity into the polymerlc material utilized to form the bat-tery separator. This siliceous pigment is highly absorbant and can absorb a substantial quantity of an aqueous or organlc liquid-whlle remaining free flowing. In practice, the amorphous precipitated sillca is loaded with the liquid and then blended with the polymeric material.
The liquid absorbed by the silica filler is subsequently removed to impart porosity to the polymer.
It has now been discovered that certaln precipitated siliceous fillers permit the fabrication of battery separators having reduced elec- -trical resistance compared to separators prepared with conventional amor-phous precipltated silica pigments, such as the aforementioned Hi-Sil~
233 silica pigment. In accordance witb the present invention9 a sili-ceous pig~ent composed of agglomerates of essentially hollow spherical precipitated siliceous partlcles is used to prepare microporous polymeric battery separators. Thls siliceous pigment is generally characterized by a surface area of between about 50 and 250 square meters per gram, a pre-dominant hollow spherical unit particle size of between 0O005 and 5.0 microns and an oil absorption of from about 150 to 300 millillters (ml~
per hundred grams of siliceous filler. The siliceous filler differs from the conventional precipitated silica pigment described, for example, in U.S. Patent 4,226,926 by the essentially hollow and spherical character of the ultimate particles of the pigment. The aforesaid siliceous pig-~ent can be prepared in accordance with the process described in U.S.
Patent 3,129,134.
~;~5~i9V
Detailed Description of the Invention _ In accordance with the present invention, between about 10 and about 90 weight percent, basis the polymerlc material, of esse~tially hollow, spherical precipitated siliceous pigment is used to produce rein-forced microporous polymeric battery separators. More particularly, between about 20 and 75, e.g., between 30 and 60, weight percent of the siliceous pigment is so used.
This siliceous pigment i8 composed of agglomerates of essen- - -tially hollow spherical particles having a predominant hollow particle size (diameter) of between 0.005 and 5.0 microns, e.g., between 0.01 and 1.0, or 0.01 and 0.20 microns. The siliceous filler is further character-ized by a surface area of between about 50 and 250 square meters per gram, (m2/gram) more typically between 75 and 200 m2/gram, and an oil absorption of from about 150 to 300, e.g., from about 200 to 300, or from about 230 to 270, ml of oil per hundred grams of slliceous filler. The surfara area of the pigment can be det~rmined by the method of Brunauer, Emmett, and Teller, J.Am. Chem. Soc., 60, 309 (1938), This method, which is often referred to as the BET method, measures the absolute surface area of a material by measuring the amount of gas adsorbed under special conditions of low temperature and pressure. The BET surface areas reported in the Examples were obtained using nitrogen as the gas adsorbed and li~uid nitrogen temperatures (-196C.) and at a 0.2 relative pres-sure. Oil absorption values are the volume o~ dibutylphthalate oil neces-sary to wet 100 grams of the pigmentO These values can be obtained using the method described in AS~ D2414-65.
The aforesaid siliceous pigment can be prepared in accordance with the process described in U.S. Patent 3,129,134. In accordance with the process therein described, the pigment is produced by precipitating 6~0 water insoluble siliceous product from an aqueous siliceous solution in the presence of finely-divided particles of a water insoluble inorganic salt, e.g., calcium carbonate - especially inorganlc salts of acids, the anhydride of which is normally gaseous, for example, the inorganic salts of carbonic acid. The water insoluble inorganic salt is then substan-tially removed from the resulting insoluble siliceous precipitate by treating the precipitate with acid, e.g, hydrochloric acid. This treat-ment converts the cation of the insoluble inorganic salt into a water-soluble salt of the treatmsnt acid and liberates the anion of the salt as a gas. Thus, treatment of calcium carbonate solids in the silica product slurry with hydrochloric acid, produces calcium chloride as the soluble salt and carbon dioxide ~or carbonic acid).
More particularly, the aforesaid described siliceous pigments are prepared by precipitating siliceous product in a slurry of f~nely-divided water-insoluble carbonate salt, most notably calcium carbonate.
The particle size of the calcium carbonate or other similar water tnsolu-ble salt of carbonic acid in the slurry should preferably approximate the desired hollow spherical particle size of the precipitated siliceous pig-ment to be used to prepare the battery separator. The calcium carbonate can be preformed and slurried in the aqueous medium in which the precipi-tation is accomplished. Alternatively, the calcium carbonate can be pre-pared, in situ, by the reaction of calcium chloride with sodium carbonate in the aqueous medium in which the precipitation is accomplished. Prod-ucts produced utilizing insoluble carbonate salts formed in situ in the reaction vessel are generally smaller in hollow spherical particle size than those obtained using slurries of preformed water insoluble carbonate salts.
i90 From the physical appe~rance of the pigment, i.e., the substan-tial absence of water insoluble siliceous material in the core of the particles, the foregoing method apparen~ly precipitates ~ater insoluble siliceous material upon the surface of the finely-divlded water-insoluble carbonate salts, e.g., calcium carbonate particles. This carbonate parti-cle is subsequently converted e.g., by acid treatment to water-soluble components, thereby leaving an essentially hollow, spherical silica particle.
The method of precipitating the water insoluble siliceous mate-rial from solution described in U~S. 3,129,134 may include partially neu-tralizing with hydrochloric acid (or like neutrallzing agent) the aqueous solution of alkali metal, e.g., sodium, silicate. The extent of this partial neutrali~ation is such tha~ the resulting aqueous solution will, upon standing (sometimes for but a very brief duration), precipitate water i~soluble siliceous material from the solutlon. Prior to develop-ing such siliceous precipitate, ~recipitation of the pigmentary siliceous material may be induced by introducing into the solution a precipita~e inducing soluble inorganic metal salt, such as calcium chloride andjor sodium chloride.
The essentially hollow, spherical siliceous pigment ~after removal of th~ water insoluble inorganic salt) is a finely-divided floccu-lated amorphous precipitated siliceous pigment. The pigment is in the form of flocs or agglomerates of quite small particles of siliceous mate-rial. The number average spherical particle size is below about p.5 micron in diameter and usually less than 0.3 micron in diameter but rarely less than 0.01 micron in dlameter. A multiplicity of these small particles are agglomerated together without complete loss of their indi-vidual identities providing the pigment's flocculated state. Flocs can ~58~
range upwards of 40 microns in si~e, as measured at their longest dlmension.
The degree to which these flocs persist (are not degradated into smaller flocs) when the pigment is subjected to mechanical action, i.e., milling, can vary. However, even those pigments which have their average floc si~e altered by mechanical means still retain the flocculant characteristic. This flocculated state appears predominantly in the form of three~dimensional clusters, which may be likened to bunches of individ-ual hollow grapes in which the particles in the floc are denoted by the individual hollow grapes and the floc is represented by the cluster.
An important feature of these precipitated siliceous pigments is the character of the ultimate particles. Such particles are composed of an optically dense outer shell (shell-like structure~ of siliceous material. The interior volume enclosed or within the shell is of much lower optical density, e.g., below the optical denslty of water-insoluble precipitated siliceous material under the high magnification of an elec-tron microscope. The ultimate particles appear almost bubble-like and spheroidal with the dif f erence in optical density between the inner and outer volumes giving them the appearance of hollow particles.
Fluids, e.g., gases or liquids, may occupy the interior volumes of the spherical particles, the dimensions of which are defined by the inner surface of the particle's siliceous shell. When well dried, little of any liqu~d, such as water, normally occupies or fills the interior volume. Typically, the siliceous shell encloses or encases completely the less optically dense interior. However, the shell is sufficiently porous to allow remo~al of the water-insoluble carbonate salt. That is, the shell is predominantlv continuous (but porous) - at least to the extent that when the interior volume is a fluid, it is possible to remove 1~5~t;90 or replace the fluid. Larger particles may have a discontinuous shell due to the non-uniform coating of large particles of ehe carbonate salt or the coating of aggregates of carbonate salt particles, i.e., non-d s-persed individual carbonate salt particles~ It is believed that the shell's porosity is composed of indirect pathways from the outslde to the inside of the shell circumventing the ultimate particles of siliceous material that make up the shell.
Chemica~ly, the slliceous pigments have a substantial SiO2 content, usually at least 50 percent by weight SiO2 on an anhydrous basis. Also commonly present are one or more metals, usually as their metal oxides, including frequently an alkaline earth metal oxide such as calcium oxide. The hollow spherical precipitated particles desirably contain less than 2 weight percent of the alkaline earth metal (measured as the oxide) for use in battery separators. Preferably, the alkaline earth metal conten~ is less than 1 weight percent, more preferably less than 0.5 weight percent and most preferably less than 0.1 weight per-cent. The alkaline earth metal content of the sillceous pigment can be reduced by treating the precipitated pigment with sufficient acid to con-vert all of the alkali~e earth metal to soluble salt and by thoroughly washing of the pigment ~after acid treatment and before drying).
After drying, the siliceous pigment is white, fluffy, pulveru-lent and dry to the touch. Despite appearing dry, the pigment normally contains water, e.g., between about 2 and 8 percent "free water" by weight. Free water is that water which is removed from the pigment by heating at 105C. for 24 hours. The pigment also contains "bound water", which refers to that water removed by heating the pigment at ignltion temperature, i.e., 1000C. to 1200C. for an extended period, e.g., 24 hours. Bound water can constitute hetween about 2 and 6 percent of the pigment.
l;~SB~ 3~
The polymeric material into which the siliceous pigment is incorporated to prepare the microporous battery separator can be any of the conventional natural and synthetic polymeric materlals conventionally used to fabricate battery separators. Among such materlals, there can be mentioned natural rubber, styrene-butadiene rubber, nitrile-butadiene -rubber, polyisoprene, high molecular weight olefins such as polyethylene, polypropylene, polybutene, ethylene-propylene copolymers, ethylene-butene copolymers, propylene-butene copolymers, ethylene-propylene-butene copoly-mers, polyvinyl chloride and vinyl chloride-vinyl acetate copolymers.
Mixtures of such materials have also been used to prepare battery separators.
Other conventional materials added to the polymeric material, such as plasticizers, antioxidants, wettlng agents, carbon black and cur-ing agents, e.g., sulfur, for rubbery polymeric materials may also be added to the composition used to prepare the battery separator.
Battery separators incorporating the above-described hollow spherical siliceous filler can be prepared in accordance with known tech-niques for preparing such articles. A typical procedure for preparing a battery separator utilizing a curable rubber is described in U.S. Patent 4,226,926. In that patent, the siliceous filler is rehydrated to levels of between 65 and 75 percent by admixing the siliceous filler with water. The resulting free flowing rehydrated silica powder is admixed with the polymeric material, e.g., in a Banbury mixer. Thereafter, the mixture (including any additional additives required for curing the poly-meric particle) is milled on a 2-roll mill to produce a milled sheet.
The milled sheet is soaked in hot water and then calendered for con-tours. Optionally a backing such as paper or a heat-bonded mat is added to the milled sheet. The calendered slleet is then cut into appropriate sizes.
1~c7c~6 J~ tt r/4 . ~ 8 Another similar procedure is described in U.S. Patent 3,351,4~5. There, the polymeric material, e.g., a polyolefin having a molecular weight of at least 300,000, ls blended with the iner~ filler~
e.g., silica, and a plasticizer. The blend, which may also contain con-ventlonal stabilizers or antioxidants, is molded or shaped, e.g., by extrusion, calendaring, injection molding or compression, ir.to sheets.
Plasticizer and/or filler is removed from the sheet by soaking the sheet in a suitable solvent, e.g., chlorinated hydrocarbons for a petroleum oil plastici~er and water, ethanol, acetone, etc. for a polyethylene glycol plasticizer.
The present invention is more particularly described in the followin~ examples which are intended as illustrative only since numerous modifications and variations thereln will be apparent to those skilled in the art.
Example I
15 liters of an aqueous solution of sodium silicate [Na20(SiO2)3 18] containing 20 grams per liter Na20 was fed at the rate of 0.5 liters per minute to one arm of a tee tube. To the other arm of the tee tube, was fed 15 liters of an aqueous solution of hydro-chloric acid containing 11.8 grams per liter ~Cl at a rate of 0.5 liters per minute. The resulting partially acidified sodium silicate solution was charged to the upper portion of a suitable reaction vessel. Added simul~aneously to the upper portion of the reaction vessel throu~h an lnlet tube was 15 liters of a salt solution containing 0.48 moles per liter of calcium chloride and 0.37 moles per liter of sodium chloride at a rate of 0.5 liters per minute. Also added to the reaction vessel through an inlet tube adjacent to the salt solution inlet tube was 15 ~Z58~
liters of an aqueous solution containing 0.16 moles per liter of sodium carbonate at a rate of 0.5 liters per minute. The reactant streams had a temperature of about 23C. The reaction mixture collected for the first 4 minutes was discarded. The remaining reaction mixture slurry was trans-ferred to a polyethylene lined vessel. This slurry was neutralized to a pH of 2.0 with 1600 milliliters of 6 Normal hydrochloric acid. The acidi-fied slurry was agitated with an air stirrer for 15 minutes and the pH of the slurry readjusted to 7.5 over 15 minutes with 138n milliliters of 2.5 Normal sodium hydroxide. The slurry was heat aged at 105~C. in an oven overnight.
Thereafter, the slurry was removed from the oven and filtered.
The filter cake was washed with 72 liters of distilled water to wash the cake free of chloride ion. The filter cake was broken-up, placed in stainless steel trays and dried overnight in an oven at 105C. The drled pigment was removed from the oven, rehumidified and micropulverized through a 0.020 inch round screen.
Optical microscopic examination of the micropulveri~ed ~aterial revealed that relatively large calcium carbonate particles were still present in the product. The amount of calcium present in the product (measured as ca~cium oxide) was found by chemical analysis to be 4.49 percent.
The product was reslurried in 10-12 liters of distilled water and sufficient 6 Normal hydrochloric acid added to the slurry to lower the pH to 2Ø The slurry was s$irred for four hours while ~aintaining the pH at 2Ø A total of 475 milliliters of hydrochloric acid was added to the slurry. Thereafter, the slurry was neutralized with 630 milli-liters of 2.5 Normal sodium h~droxide to raise the pH of the slurry to 7.65. The slurry was filtered and the filter cake washed with 24 liters .~S8~;9~
of distilled water. The washed filter cake was dried overnight at 105C.
in an oven and thereafter micropulveriz.ed through a 0.020 lnch round screen. The micropulveri~ed product was rehumidified by exposure to ambient alr over a weekend.
The resulting product was submitted for surface area and oil absorption determinations, and elemental X-ray analysis. Results are tabulated in Table I.
Example II
18 liters of an aqueous solution of sodium silicate [~a2O(SiO2)3 18] containing 10.5 grams per liter Na20 was fed at the rate of 0.5 liters per minute to one arm of a tee tube. To the other arm of the tee tube was fed 18 liters of hydrochloric acid containing 0.187 grams per liter HCl at a rate of 0.5 liters per mlnu~e. Simultane-ously, 36 liters of a salt solution (calcium chloride plus sodium chlo-ride) containing 57 grams/liter o~ Camel-Wite Super~ ~round calcium car-bonate of approximately 3 micron particles were added to the reaction vessel. The salt solution contained 0.169 moles per liter of calcium chloride and 0.128 moles per liter of sodium chloride. The salt slurry was introduced into the reaction zone at a rate of 1.0 liters per minute. The temperature in the reaction vessel was about 18C. The first 4 1/2 minutes of slurry produced was discarded and thereafter the resulting slurry collected. The pH of the product slurry after addition of all of the reactants was 9Ø The pH of the slurry was adjusted to
BATTERY SEPARATOR
Description of the Inventlon The present invention is dlrec~ed to a siliceous filler-contain-lng battery separator. In commonly used electrlc storage batteries, such as the well-known 12-volt battery employed in automobiles, separators are placed between bat~ery plates of opposite polarity to prevent the two plates from touching each other and causing an electrical short. The separator is typically a microporous article fabrlcated from a polymeric material, e.g., natural or synthetic rubber, or a polyolefin. The separa-tor may ha~e a backing material of, for example, a non-woven web. The pore size of the microporous separator should be as small as possible since this reduces the danger of active materials being forced through or growing through the separator, thereby causing an electrical short.
The separator should also have a low electrical resistance in order to maximize the power output from the battery. Lower electrical resistance can be obtained by reducing the overall thickness of the sepa rator, e.g., the thickness of the backing material; however~ thinner sepa-rators are more subject to corrosion and other physical factors affecting the service life of the separator.
Certain siliceous fillers have been used to prepare mlcroporous battery separators. See, for example, U.S. Patent 2,302,832, which describes the use of a silica hydrogel in a rubber binder, U.S. Patent 3,351,495, which describes synthetic and natural zeolites, precipltated metal silicates, such ~s calcium silicate, and silica gels as the inor-ganic filler and extender for separators of high molecular weight poly-olefins, and U.S. Patents 3,696,061, 4,226,926, and 49237,083, which describe the use of finely di~ided, precipitated amorphous s-llica, such as E1i-Sil~ 233 siliceous pigment, in microporous battery separators.
Typlcally, amorphous precipitated slllca plgment is used to introduce porosity into the polymerlc material utilized to form the bat-tery separator. This siliceous pigment is highly absorbant and can absorb a substantial quantity of an aqueous or organlc liquid-whlle remaining free flowing. In practice, the amorphous precipitated sillca is loaded with the liquid and then blended with the polymeric material.
The liquid absorbed by the silica filler is subsequently removed to impart porosity to the polymer.
It has now been discovered that certaln precipitated siliceous fillers permit the fabrication of battery separators having reduced elec- -trical resistance compared to separators prepared with conventional amor-phous precipltated silica pigments, such as the aforementioned Hi-Sil~
233 silica pigment. In accordance witb the present invention9 a sili-ceous pig~ent composed of agglomerates of essentially hollow spherical precipitated siliceous partlcles is used to prepare microporous polymeric battery separators. Thls siliceous pigment is generally characterized by a surface area of between about 50 and 250 square meters per gram, a pre-dominant hollow spherical unit particle size of between 0O005 and 5.0 microns and an oil absorption of from about 150 to 300 millillters (ml~
per hundred grams of siliceous filler. The siliceous filler differs from the conventional precipitated silica pigment described, for example, in U.S. Patent 4,226,926 by the essentially hollow and spherical character of the ultimate particles of the pigment. The aforesaid siliceous pig-~ent can be prepared in accordance with the process described in U.S.
Patent 3,129,134.
~;~5~i9V
Detailed Description of the Invention _ In accordance with the present invention, between about 10 and about 90 weight percent, basis the polymerlc material, of esse~tially hollow, spherical precipitated siliceous pigment is used to produce rein-forced microporous polymeric battery separators. More particularly, between about 20 and 75, e.g., between 30 and 60, weight percent of the siliceous pigment is so used.
This siliceous pigment i8 composed of agglomerates of essen- - -tially hollow spherical particles having a predominant hollow particle size (diameter) of between 0.005 and 5.0 microns, e.g., between 0.01 and 1.0, or 0.01 and 0.20 microns. The siliceous filler is further character-ized by a surface area of between about 50 and 250 square meters per gram, (m2/gram) more typically between 75 and 200 m2/gram, and an oil absorption of from about 150 to 300, e.g., from about 200 to 300, or from about 230 to 270, ml of oil per hundred grams of slliceous filler. The surfara area of the pigment can be det~rmined by the method of Brunauer, Emmett, and Teller, J.Am. Chem. Soc., 60, 309 (1938), This method, which is often referred to as the BET method, measures the absolute surface area of a material by measuring the amount of gas adsorbed under special conditions of low temperature and pressure. The BET surface areas reported in the Examples were obtained using nitrogen as the gas adsorbed and li~uid nitrogen temperatures (-196C.) and at a 0.2 relative pres-sure. Oil absorption values are the volume o~ dibutylphthalate oil neces-sary to wet 100 grams of the pigmentO These values can be obtained using the method described in AS~ D2414-65.
The aforesaid siliceous pigment can be prepared in accordance with the process described in U.S. Patent 3,129,134. In accordance with the process therein described, the pigment is produced by precipitating 6~0 water insoluble siliceous product from an aqueous siliceous solution in the presence of finely-divided particles of a water insoluble inorganic salt, e.g., calcium carbonate - especially inorganlc salts of acids, the anhydride of which is normally gaseous, for example, the inorganic salts of carbonic acid. The water insoluble inorganic salt is then substan-tially removed from the resulting insoluble siliceous precipitate by treating the precipitate with acid, e.g, hydrochloric acid. This treat-ment converts the cation of the insoluble inorganic salt into a water-soluble salt of the treatmsnt acid and liberates the anion of the salt as a gas. Thus, treatment of calcium carbonate solids in the silica product slurry with hydrochloric acid, produces calcium chloride as the soluble salt and carbon dioxide ~or carbonic acid).
More particularly, the aforesaid described siliceous pigments are prepared by precipitating siliceous product in a slurry of f~nely-divided water-insoluble carbonate salt, most notably calcium carbonate.
The particle size of the calcium carbonate or other similar water tnsolu-ble salt of carbonic acid in the slurry should preferably approximate the desired hollow spherical particle size of the precipitated siliceous pig-ment to be used to prepare the battery separator. The calcium carbonate can be preformed and slurried in the aqueous medium in which the precipi-tation is accomplished. Alternatively, the calcium carbonate can be pre-pared, in situ, by the reaction of calcium chloride with sodium carbonate in the aqueous medium in which the precipitation is accomplished. Prod-ucts produced utilizing insoluble carbonate salts formed in situ in the reaction vessel are generally smaller in hollow spherical particle size than those obtained using slurries of preformed water insoluble carbonate salts.
i90 From the physical appe~rance of the pigment, i.e., the substan-tial absence of water insoluble siliceous material in the core of the particles, the foregoing method apparen~ly precipitates ~ater insoluble siliceous material upon the surface of the finely-divlded water-insoluble carbonate salts, e.g., calcium carbonate particles. This carbonate parti-cle is subsequently converted e.g., by acid treatment to water-soluble components, thereby leaving an essentially hollow, spherical silica particle.
The method of precipitating the water insoluble siliceous mate-rial from solution described in U~S. 3,129,134 may include partially neu-tralizing with hydrochloric acid (or like neutrallzing agent) the aqueous solution of alkali metal, e.g., sodium, silicate. The extent of this partial neutrali~ation is such tha~ the resulting aqueous solution will, upon standing (sometimes for but a very brief duration), precipitate water i~soluble siliceous material from the solutlon. Prior to develop-ing such siliceous precipitate, ~recipitation of the pigmentary siliceous material may be induced by introducing into the solution a precipita~e inducing soluble inorganic metal salt, such as calcium chloride andjor sodium chloride.
The essentially hollow, spherical siliceous pigment ~after removal of th~ water insoluble inorganic salt) is a finely-divided floccu-lated amorphous precipitated siliceous pigment. The pigment is in the form of flocs or agglomerates of quite small particles of siliceous mate-rial. The number average spherical particle size is below about p.5 micron in diameter and usually less than 0.3 micron in diameter but rarely less than 0.01 micron in dlameter. A multiplicity of these small particles are agglomerated together without complete loss of their indi-vidual identities providing the pigment's flocculated state. Flocs can ~58~
range upwards of 40 microns in si~e, as measured at their longest dlmension.
The degree to which these flocs persist (are not degradated into smaller flocs) when the pigment is subjected to mechanical action, i.e., milling, can vary. However, even those pigments which have their average floc si~e altered by mechanical means still retain the flocculant characteristic. This flocculated state appears predominantly in the form of three~dimensional clusters, which may be likened to bunches of individ-ual hollow grapes in which the particles in the floc are denoted by the individual hollow grapes and the floc is represented by the cluster.
An important feature of these precipitated siliceous pigments is the character of the ultimate particles. Such particles are composed of an optically dense outer shell (shell-like structure~ of siliceous material. The interior volume enclosed or within the shell is of much lower optical density, e.g., below the optical denslty of water-insoluble precipitated siliceous material under the high magnification of an elec-tron microscope. The ultimate particles appear almost bubble-like and spheroidal with the dif f erence in optical density between the inner and outer volumes giving them the appearance of hollow particles.
Fluids, e.g., gases or liquids, may occupy the interior volumes of the spherical particles, the dimensions of which are defined by the inner surface of the particle's siliceous shell. When well dried, little of any liqu~d, such as water, normally occupies or fills the interior volume. Typically, the siliceous shell encloses or encases completely the less optically dense interior. However, the shell is sufficiently porous to allow remo~al of the water-insoluble carbonate salt. That is, the shell is predominantlv continuous (but porous) - at least to the extent that when the interior volume is a fluid, it is possible to remove 1~5~t;90 or replace the fluid. Larger particles may have a discontinuous shell due to the non-uniform coating of large particles of ehe carbonate salt or the coating of aggregates of carbonate salt particles, i.e., non-d s-persed individual carbonate salt particles~ It is believed that the shell's porosity is composed of indirect pathways from the outslde to the inside of the shell circumventing the ultimate particles of siliceous material that make up the shell.
Chemica~ly, the slliceous pigments have a substantial SiO2 content, usually at least 50 percent by weight SiO2 on an anhydrous basis. Also commonly present are one or more metals, usually as their metal oxides, including frequently an alkaline earth metal oxide such as calcium oxide. The hollow spherical precipitated particles desirably contain less than 2 weight percent of the alkaline earth metal (measured as the oxide) for use in battery separators. Preferably, the alkaline earth metal conten~ is less than 1 weight percent, more preferably less than 0.5 weight percent and most preferably less than 0.1 weight per-cent. The alkaline earth metal content of the sillceous pigment can be reduced by treating the precipitated pigment with sufficient acid to con-vert all of the alkali~e earth metal to soluble salt and by thoroughly washing of the pigment ~after acid treatment and before drying).
After drying, the siliceous pigment is white, fluffy, pulveru-lent and dry to the touch. Despite appearing dry, the pigment normally contains water, e.g., between about 2 and 8 percent "free water" by weight. Free water is that water which is removed from the pigment by heating at 105C. for 24 hours. The pigment also contains "bound water", which refers to that water removed by heating the pigment at ignltion temperature, i.e., 1000C. to 1200C. for an extended period, e.g., 24 hours. Bound water can constitute hetween about 2 and 6 percent of the pigment.
l;~SB~ 3~
The polymeric material into which the siliceous pigment is incorporated to prepare the microporous battery separator can be any of the conventional natural and synthetic polymeric materlals conventionally used to fabricate battery separators. Among such materlals, there can be mentioned natural rubber, styrene-butadiene rubber, nitrile-butadiene -rubber, polyisoprene, high molecular weight olefins such as polyethylene, polypropylene, polybutene, ethylene-propylene copolymers, ethylene-butene copolymers, propylene-butene copolymers, ethylene-propylene-butene copoly-mers, polyvinyl chloride and vinyl chloride-vinyl acetate copolymers.
Mixtures of such materials have also been used to prepare battery separators.
Other conventional materials added to the polymeric material, such as plasticizers, antioxidants, wettlng agents, carbon black and cur-ing agents, e.g., sulfur, for rubbery polymeric materials may also be added to the composition used to prepare the battery separator.
Battery separators incorporating the above-described hollow spherical siliceous filler can be prepared in accordance with known tech-niques for preparing such articles. A typical procedure for preparing a battery separator utilizing a curable rubber is described in U.S. Patent 4,226,926. In that patent, the siliceous filler is rehydrated to levels of between 65 and 75 percent by admixing the siliceous filler with water. The resulting free flowing rehydrated silica powder is admixed with the polymeric material, e.g., in a Banbury mixer. Thereafter, the mixture (including any additional additives required for curing the poly-meric particle) is milled on a 2-roll mill to produce a milled sheet.
The milled sheet is soaked in hot water and then calendered for con-tours. Optionally a backing such as paper or a heat-bonded mat is added to the milled sheet. The calendered slleet is then cut into appropriate sizes.
1~c7c~6 J~ tt r/4 . ~ 8 Another similar procedure is described in U.S. Patent 3,351,4~5. There, the polymeric material, e.g., a polyolefin having a molecular weight of at least 300,000, ls blended with the iner~ filler~
e.g., silica, and a plasticizer. The blend, which may also contain con-ventlonal stabilizers or antioxidants, is molded or shaped, e.g., by extrusion, calendaring, injection molding or compression, ir.to sheets.
Plasticizer and/or filler is removed from the sheet by soaking the sheet in a suitable solvent, e.g., chlorinated hydrocarbons for a petroleum oil plastici~er and water, ethanol, acetone, etc. for a polyethylene glycol plasticizer.
The present invention is more particularly described in the followin~ examples which are intended as illustrative only since numerous modifications and variations thereln will be apparent to those skilled in the art.
Example I
15 liters of an aqueous solution of sodium silicate [Na20(SiO2)3 18] containing 20 grams per liter Na20 was fed at the rate of 0.5 liters per minute to one arm of a tee tube. To the other arm of the tee tube, was fed 15 liters of an aqueous solution of hydro-chloric acid containing 11.8 grams per liter ~Cl at a rate of 0.5 liters per minute. The resulting partially acidified sodium silicate solution was charged to the upper portion of a suitable reaction vessel. Added simul~aneously to the upper portion of the reaction vessel throu~h an lnlet tube was 15 liters of a salt solution containing 0.48 moles per liter of calcium chloride and 0.37 moles per liter of sodium chloride at a rate of 0.5 liters per minute. Also added to the reaction vessel through an inlet tube adjacent to the salt solution inlet tube was 15 ~Z58~
liters of an aqueous solution containing 0.16 moles per liter of sodium carbonate at a rate of 0.5 liters per minute. The reactant streams had a temperature of about 23C. The reaction mixture collected for the first 4 minutes was discarded. The remaining reaction mixture slurry was trans-ferred to a polyethylene lined vessel. This slurry was neutralized to a pH of 2.0 with 1600 milliliters of 6 Normal hydrochloric acid. The acidi-fied slurry was agitated with an air stirrer for 15 minutes and the pH of the slurry readjusted to 7.5 over 15 minutes with 138n milliliters of 2.5 Normal sodium hydroxide. The slurry was heat aged at 105~C. in an oven overnight.
Thereafter, the slurry was removed from the oven and filtered.
The filter cake was washed with 72 liters of distilled water to wash the cake free of chloride ion. The filter cake was broken-up, placed in stainless steel trays and dried overnight in an oven at 105C. The drled pigment was removed from the oven, rehumidified and micropulverized through a 0.020 inch round screen.
Optical microscopic examination of the micropulveri~ed ~aterial revealed that relatively large calcium carbonate particles were still present in the product. The amount of calcium present in the product (measured as ca~cium oxide) was found by chemical analysis to be 4.49 percent.
The product was reslurried in 10-12 liters of distilled water and sufficient 6 Normal hydrochloric acid added to the slurry to lower the pH to 2Ø The slurry was s$irred for four hours while ~aintaining the pH at 2Ø A total of 475 milliliters of hydrochloric acid was added to the slurry. Thereafter, the slurry was neutralized with 630 milli-liters of 2.5 Normal sodium h~droxide to raise the pH of the slurry to 7.65. The slurry was filtered and the filter cake washed with 24 liters .~S8~;9~
of distilled water. The washed filter cake was dried overnight at 105C.
in an oven and thereafter micropulveriz.ed through a 0.020 lnch round screen. The micropulveri~ed product was rehumidified by exposure to ambient alr over a weekend.
The resulting product was submitted for surface area and oil absorption determinations, and elemental X-ray analysis. Results are tabulated in Table I.
Example II
18 liters of an aqueous solution of sodium silicate [~a2O(SiO2)3 18] containing 10.5 grams per liter Na20 was fed at the rate of 0.5 liters per minute to one arm of a tee tube. To the other arm of the tee tube was fed 18 liters of hydrochloric acid containing 0.187 grams per liter HCl at a rate of 0.5 liters per mlnu~e. Simultane-ously, 36 liters of a salt solution (calcium chloride plus sodium chlo-ride) containing 57 grams/liter o~ Camel-Wite Super~ ~round calcium car-bonate of approximately 3 micron particles were added to the reaction vessel. The salt solution contained 0.169 moles per liter of calcium chloride and 0.128 moles per liter of sodium chloride. The salt slurry was introduced into the reaction zone at a rate of 1.0 liters per minute. The temperature in the reaction vessel was about 18C. The first 4 1/2 minutes of slurry produced was discarded and thereafter the resulting slurry collected. The pH of the product slurry after addition of all of the reactants was 9Ø The pH of the slurry was adjusted to
2.0 with 6.0 liters of 6 ~ormal hydrochloric acid. The acidified slurry was stirrPd for 20 minutes and thereafter the pH adjusted to 8.0 with 2520 milliliters of 2.5 Normal sodium hydroxide. The resulting slurry was heat aged ovPrnight at 105C.
~S~
The aged slurry was removed~ ~acuum filtered and the filter cake washed ~ith 112 liters of dlstilled water. The filter cake was broken-up and dried overnight in an oven at 105C. The dried product was rehumid~fied and then micropulverized through a 0.020 inch round screen.
Optical microscopic examination of the milled pigment showed large calcium carbonate particles still present in the sample. The amount of calcium present (measured as calcium oxide) was found to be 13.3~ weight percent CaO. Accordingly, the product was reslurried in 10 to 12 liters of distilled water and 960 milliliters of 6 Normal hydro-chloric acid added to the slurry to reduce the pH to 2Ø The acidified slurry was stirred for 4 hours and thereafter 310 milliliters of 2.5 Nor-mal sodium hydroxide added to raise the pll of the slurry to 7.70. The neutralized slurry was filtered and the filter cake washed with 32 liters of distilled water. The filter cake was broken-up and dried overnight in an oven at 105C. The dried pigment was micropulverized through a 0.020 inch round screen. The resulting product was submitted for surface area and oil absorption determinations, and elemental Y.-ray analysis. Results are tabulated in Table I.
Example III
In a manner similar to Example I, 36 liters of an aqueous solu-tion of sodium silicate [Na2O(SiO2)3 06] contailling 20 grams per liter NazO was charged at a rate of 0.5 liters per minute into one arm of a tee tube. Through the other arm of the tee tube was charged 36 liters of hydrochloric acid contalning 11.8 grams per liter at a rate of 0.5 liters per minute. The concentration of the calcium chloride/sodium chloride salt solution and sodium carbonate solution were the same as in ~s~
Example I e~cept that 36 liters of each solution were lneroduced in~o the reaction vessel at a rate of O.S l$ters per minute. The temperature within the reaction vessel was about 23-24C. The resulting product slurry had a pH oE 9.15. The pH of the slurry was adjusted to 2.0 with
~S~
The aged slurry was removed~ ~acuum filtered and the filter cake washed ~ith 112 liters of dlstilled water. The filter cake was broken-up and dried overnight in an oven at 105C. The dried product was rehumid~fied and then micropulverized through a 0.020 inch round screen.
Optical microscopic examination of the milled pigment showed large calcium carbonate particles still present in the sample. The amount of calcium present (measured as calcium oxide) was found to be 13.3~ weight percent CaO. Accordingly, the product was reslurried in 10 to 12 liters of distilled water and 960 milliliters of 6 Normal hydro-chloric acid added to the slurry to reduce the pH to 2Ø The acidified slurry was stirred for 4 hours and thereafter 310 milliliters of 2.5 Nor-mal sodium hydroxide added to raise the pll of the slurry to 7.70. The neutralized slurry was filtered and the filter cake washed with 32 liters of distilled water. The filter cake was broken-up and dried overnight in an oven at 105C. The dried pigment was micropulverized through a 0.020 inch round screen. The resulting product was submitted for surface area and oil absorption determinations, and elemental Y.-ray analysis. Results are tabulated in Table I.
Example III
In a manner similar to Example I, 36 liters of an aqueous solu-tion of sodium silicate [Na2O(SiO2)3 06] contailling 20 grams per liter NazO was charged at a rate of 0.5 liters per minute into one arm of a tee tube. Through the other arm of the tee tube was charged 36 liters of hydrochloric acid contalning 11.8 grams per liter at a rate of 0.5 liters per minute. The concentration of the calcium chloride/sodium chloride salt solution and sodium carbonate solution were the same as in ~s~
Example I e~cept that 36 liters of each solution were lneroduced in~o the reaction vessel at a rate of O.S l$ters per minute. The temperature within the reaction vessel was about 23-24C. The resulting product slurry had a pH oE 9.15. The pH of the slurry was adjusted to 2.0 with
3.9 liters of 6 Normal hydrochloric acid and stirred for 3 hours at that pH. Subsequently, the acidified slurry was neutralized to a pH of 7.8 with 2.4 liters oE 2.5 Normal sodium hydroxide. The neutralized slurry was aged overnight in an oven at 105C. and the aged slurry filtered and washed with 96 liters of dist~lled water. The washed filter cake was dried overnight in a 105C. ovan. The dried product was rehumidified at room temperature and micropulverized (hammer milled) through a 0.01 inch screen~
The resulting product was submitted for X-Ray elemental analy-sis and surface area and oil absorption determinations. Results are tabu-lated ln Table I.
Examp]e I~ -The procedure of Example II was followed utilizing 18 liters of the aqueous sodium silica~e solution described in Example III. The sodium silicate solution was partially neutralized with 1~ liters of hydrochloric acid containin~ 12.9 ~rams per liter of ~Cl charged at a rate of 0.5 llters per minute. 36 liters of a salt solution containing 0.65 moles per liter calcium chloride and 0.51 moles per liter sodium chloride was introduced into the reaction vessel at a rate of 1 Liter per mlnute. The salt solution contained 0.57 moles (57 grams) p~r liter of preformed calcium carbonate having an average particle size of 0.75 microns. The temperature in the reaction vessel was about 19C. The p~1 of the resulting slurry following addition of all of the reactants was 3! ;~5~ ;<3(~
8.6. The pH of the slurry was ad~usted to 2.0 wlth 4,82 liters of 6 Nor-mal hydrochloric acid and the acidified slurry stirred for 4 hours at a pH of 2. Subsequently, the aged acidified slurry was neutrali~ed wlth 1.34 liters of 2.5 Normal sodium hydroxide to a pH of 7.8. The neutral-ized slurry was aged overnight at 105C. and subse~uently filtered. The filter cake was washed with 128 liters of distilled water and the washed fllter cake dried overnight in a 105C. oven. The dried product was rehumidified at room temperature and micropulverized through a 0.01 inch screen. The milled product was submitted for physical and chemical analy-sis. Results are tabulated in Table I.
TABLE I
Example Particle Size* Surfa~e Oil Abs, ~ X-Ray Analysis, Wt. %
No. Range, um Area~ m ¦g ml/100 g H20 Ca Cl Fe Na Al M
I 0.009-0.07133 210 3.46 0.50 0.05 0.12 0.19 0.34 <0.0 II 0.1-5.0 80 189 4.58 1.4 0.41 0.40 0.13 0.43 0.2 III 0.02~0.08102 249 4.72 1.5 0.12 0.09 0.33 0.29 0.2 IV 0.2-1.0 57 263 5.65 1.6 0.55 0.15 0.54 0.28 0.6 * Predominan~ Ultimate Particles ~Jater content was determined by measuring weight loss of the sample after heating at 105C.
The product of ~xample III was substituted for a conventional precipitated silica pigment in a battery separator and the resulting sepa-rator was reported to exhibit a reduction in electrical resistance of ~rom 15 to 20 percent.
From the foregoing examples, it is clear that various proce-dures and reagents may be used in preparing the hollow silica plgments descrlbed herein. Any suitable water soluble alkali metal sillcate, for examples, serves as a source of the S10~ content of the ultimate pig-5~:;9~
ment product. Sodium silicate containing from ~ to 4 moles SlO2 permole of Na20 is the more widely available and used material. Others, including potassium silicate, lithium silicate and sodium potassium sili-cate containing from 1 to 5 moles of SiO2 per mole of alkali metal oxide, however, may also be used.
The salt which induces precipitntion of the water insoluble siliceous material also can be varied. It is usually preferably that the salt be a water soluble halide, notably a chloride, such as calcium chlo ride. Among the salts which may be so used include: sodium chloride, barium chloride, strontium chloride, zinc chloride, calcium bromide, sodium ioaide, water soluble metal salts of strong acids, e.g., acids having an ionizatlon constan~ of at least 1 X 10 2, such as metal nitrates exemplified by calcium nitrate and sodium nitrate, and metal sulfates such as sodium sulfate.
As with the other reagents, there is latitude in the acidic material used to partlally neutralize the aqueous solution of alkali metal silicate. Acids such as hydrochloric acid, sulfurlc acid, nitric acid, acetic acid, sulfurous acid, phosphorlc acid and carbonic acid (or thelr anhydrides) can be mentioned. In the main, preference is for acidic materlals, the anions of which do not form water insoluble mate-rials under the prevailing conditions with alkali metalsn Acids or acidic materials that may be used in treating the slurry of precipitated water insoluble siliceous material for the purpose of water solubilizing the water insoluble non-siliceous materia~, such as calcium carbonate may also vary. Most typically 9 such acids are those which, upon reaction with the aforesaid water insoluble material will provide a water soluble salt of the cation aDd result in generating 2n anhydride of the anion of the water insoluble material, such as carbon 5~6"3~
dio~ide t~hen the material is calcium carbonate. For this purpose, strong mineral acids such as hydrochloric~ and nitric acids are suggested.
While the invention has been described in deta$1 with respect to certain embodiments thereof, it is to be understood that the invention is not intended to be limited to such details except as and insofar as they appear in the appended claims.
The resulting product was submitted for X-Ray elemental analy-sis and surface area and oil absorption determinations. Results are tabu-lated ln Table I.
Examp]e I~ -The procedure of Example II was followed utilizing 18 liters of the aqueous sodium silica~e solution described in Example III. The sodium silicate solution was partially neutralized with 1~ liters of hydrochloric acid containin~ 12.9 ~rams per liter of ~Cl charged at a rate of 0.5 llters per minute. 36 liters of a salt solution containing 0.65 moles per liter calcium chloride and 0.51 moles per liter sodium chloride was introduced into the reaction vessel at a rate of 1 Liter per mlnute. The salt solution contained 0.57 moles (57 grams) p~r liter of preformed calcium carbonate having an average particle size of 0.75 microns. The temperature in the reaction vessel was about 19C. The p~1 of the resulting slurry following addition of all of the reactants was 3! ;~5~ ;<3(~
8.6. The pH of the slurry was ad~usted to 2.0 wlth 4,82 liters of 6 Nor-mal hydrochloric acid and the acidified slurry stirred for 4 hours at a pH of 2. Subsequently, the aged acidified slurry was neutrali~ed wlth 1.34 liters of 2.5 Normal sodium hydroxide to a pH of 7.8. The neutral-ized slurry was aged overnight at 105C. and subse~uently filtered. The filter cake was washed with 128 liters of distilled water and the washed fllter cake dried overnight in a 105C. oven. The dried product was rehumidified at room temperature and micropulverized through a 0.01 inch screen. The milled product was submitted for physical and chemical analy-sis. Results are tabulated in Table I.
TABLE I
Example Particle Size* Surfa~e Oil Abs, ~ X-Ray Analysis, Wt. %
No. Range, um Area~ m ¦g ml/100 g H20 Ca Cl Fe Na Al M
I 0.009-0.07133 210 3.46 0.50 0.05 0.12 0.19 0.34 <0.0 II 0.1-5.0 80 189 4.58 1.4 0.41 0.40 0.13 0.43 0.2 III 0.02~0.08102 249 4.72 1.5 0.12 0.09 0.33 0.29 0.2 IV 0.2-1.0 57 263 5.65 1.6 0.55 0.15 0.54 0.28 0.6 * Predominan~ Ultimate Particles ~Jater content was determined by measuring weight loss of the sample after heating at 105C.
The product of ~xample III was substituted for a conventional precipitated silica pigment in a battery separator and the resulting sepa-rator was reported to exhibit a reduction in electrical resistance of ~rom 15 to 20 percent.
From the foregoing examples, it is clear that various proce-dures and reagents may be used in preparing the hollow silica plgments descrlbed herein. Any suitable water soluble alkali metal sillcate, for examples, serves as a source of the S10~ content of the ultimate pig-5~:;9~
ment product. Sodium silicate containing from ~ to 4 moles SlO2 permole of Na20 is the more widely available and used material. Others, including potassium silicate, lithium silicate and sodium potassium sili-cate containing from 1 to 5 moles of SiO2 per mole of alkali metal oxide, however, may also be used.
The salt which induces precipitntion of the water insoluble siliceous material also can be varied. It is usually preferably that the salt be a water soluble halide, notably a chloride, such as calcium chlo ride. Among the salts which may be so used include: sodium chloride, barium chloride, strontium chloride, zinc chloride, calcium bromide, sodium ioaide, water soluble metal salts of strong acids, e.g., acids having an ionizatlon constan~ of at least 1 X 10 2, such as metal nitrates exemplified by calcium nitrate and sodium nitrate, and metal sulfates such as sodium sulfate.
As with the other reagents, there is latitude in the acidic material used to partlally neutralize the aqueous solution of alkali metal silicate. Acids such as hydrochloric acid, sulfurlc acid, nitric acid, acetic acid, sulfurous acid, phosphorlc acid and carbonic acid (or thelr anhydrides) can be mentioned. In the main, preference is for acidic materlals, the anions of which do not form water insoluble mate-rials under the prevailing conditions with alkali metalsn Acids or acidic materials that may be used in treating the slurry of precipitated water insoluble siliceous material for the purpose of water solubilizing the water insoluble non-siliceous materia~, such as calcium carbonate may also vary. Most typically 9 such acids are those which, upon reaction with the aforesaid water insoluble material will provide a water soluble salt of the cation aDd result in generating 2n anhydride of the anion of the water insoluble material, such as carbon 5~6"3~
dio~ide t~hen the material is calcium carbonate. For this purpose, strong mineral acids such as hydrochloric~ and nitric acids are suggested.
While the invention has been described in deta$1 with respect to certain embodiments thereof, it is to be understood that the invention is not intended to be limited to such details except as and insofar as they appear in the appended claims.
Claims (8)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a siliceous filler-reinforced microporous polymeric bat-tery separator, the improvement wherein the siliceous filler comprises agglomerates of essentially hollow spherical particles of-amorphous, pre-cipitated silica having a predominant hollow spherical particle size of between 0.005 and 5.0 microns, said siliceous filler having a surface area of between about 50 and 200 square meters per gram, and an oil absorption of from about 150 to 300 milliliters per 100 grams of filler.
2. The battery separator of claim 1 wherein between about 20 and about 75 weight percent of siliceous filler, basis the polymeric mate-rial, is used to prepare the separator.
3. The battery separator of claim 1 wherein the siliceous filler comprises agglomerates of essentially hollow spherical particles having a predominant hollow spherical particle size of between 0.01 and 1.0 microns, has a surface area of between 75 and 200 square meters per gram, and an oil absorption of from about 200 to 300 milliliters per 100 grams of filler.
4. The battery separator of claim 3 wherein the predominant hollow spherical particle size is between 0.01 and 0.20 microns and the oil absorption is from about 230 to 270 milliliters.
5. The battery separator of claim 1 wherein the polymeric mate-rial is selected from natural rubber, styrene-butadiene rubber, nitrile-butadiene rubber, polyisoprene, high molecular weight polyethylene, poly-propylene, polybutene, ethylene-propylene copolymers, polyvinyl chloride and vinyl chloride-vinyl acetate copolymers.
6. The battery separator of claim 5 wherein between about 20 and 75 weight percent of siliceous filler, basis the polymeric material, is used to prepare the separator.
7. A microporous, siliceous filler-reinforced polymeric sheet of a size and configuration adapted to fit between and separate the plates of a battery, the polymeric material of said sheet being selected from the materials consisting essentially of natural rubber, styrene-butadiene rubber, polyisoprene, high molecular weight polyethylene, poly-propylene, ethylene-propylene copolymers and polyvinyl chloride, said siliceous filler being composed of agglomerates of essentially hollow spherical particles of amorphous, precipitated silica having a predomi-nant hollow spherical particle size of between 0.01 and 1.0 microns, hav-ing a surface area of between 75 and 200 square meters per gram and an oil absorption of from about 200 to 300 milliliters per 100 grams of filler.
8. The polymeric sheet of claim 7 wherein between 20 and 75 weight percent of siliceous filler, basis the polymeric material, is used to prepare the polymeric sheet.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US67421884A | 1984-11-23 | 1984-11-23 | |
| US674,218 | 1984-11-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1258690A true CA1258690A (en) | 1989-08-22 |
Family
ID=24705784
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000494463A Expired CA1258690A (en) | 1984-11-23 | 1985-11-01 | Battery separator |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1258690A (en) |
| DE (1) | DE3540718A1 (en) |
| FR (1) | FR2573921B1 (en) |
| GB (1) | GB2167600B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3626096C2 (en) * | 1986-07-31 | 1994-09-01 | Vb Autobatterie Gmbh | Separator fleece for maintenance-free lead accumulators |
| US5009971A (en) * | 1987-03-13 | 1991-04-23 | Ppg Industries, Inc. | Gas recombinant separator |
| DE3922160A1 (en) * | 1989-07-06 | 1991-01-10 | Grace Gmbh | LEAD / SULFURIC ACID ACCUMULATOR, SEPARATOR FOR LEAD / SULFURIC ACID ACCUMULATOR AND METHOD FOR REDUCING THE FORMATION OF DARK DEPOSITS IN A LEAD / SULFURIC ACID ACCUMULATOR |
| US20030022068A1 (en) * | 2001-05-23 | 2003-01-30 | Pekala Richard W. | Lead acid battery separator with improved electrical and mechanical properties |
| US6998193B2 (en) * | 2001-12-28 | 2006-02-14 | Policell Technologies, Inc. | Microporous membrane and its uses thereof |
| DE10216418B4 (en) | 2002-04-12 | 2006-02-09 | Daramic, Inc. | Battery separator, use of a battery separator, method of making a battery separator and use of a connection |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1092407A (en) * | 1953-10-19 | 1955-04-21 | Du Pont | Surface esterified siliceous solids and their uses |
| US2912479A (en) * | 1957-04-11 | 1959-11-10 | Koehler Mfg Co | Separators for storage batteries and method of making them |
| NL275296A (en) * | 1961-03-21 | |||
| US3351495A (en) * | 1966-11-22 | 1967-11-07 | Grace W R & Co | Battery separator |
| US3696061A (en) * | 1970-04-13 | 1972-10-03 | Amerace Esna Corp | Method for forming flowable powder processable into microporous object |
| NL7014811A (en) * | 1970-10-09 | 1972-04-11 | ||
| JPS5819689B2 (en) * | 1975-06-18 | 1983-04-19 | 旭化成株式会社 | Takoumaku |
| US4173491A (en) * | 1978-03-03 | 1979-11-06 | E. I. Du Pont De Nemours And Company | Pigmented microporous silica microspheres by spray processes |
| US4226926A (en) * | 1978-06-16 | 1980-10-07 | Amerace Corporation | Flexible, microporous rubber base articles |
-
1985
- 1985-11-01 CA CA000494463A patent/CA1258690A/en not_active Expired
- 1985-11-16 DE DE19853540718 patent/DE3540718A1/en active Granted
- 1985-11-22 FR FR8517338A patent/FR2573921B1/en not_active Expired
- 1985-11-22 GB GB08528876A patent/GB2167600B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3540718C2 (en) | 1988-10-27 |
| GB2167600B (en) | 1987-12-23 |
| GB8528876D0 (en) | 1985-12-24 |
| FR2573921A1 (en) | 1986-05-30 |
| DE3540718A1 (en) | 1986-05-28 |
| FR2573921B1 (en) | 1988-02-26 |
| GB2167600A (en) | 1986-05-29 |
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