US2290496A - Method of making storage battery separators - Google Patents

Description

Patented July 2i, W42

METHOD OF MAKHNG STORAGE BATTERY SEPARATORS Bruno El. Schubert, Weehawken, N. .lL, assignor to National Lead Company, New York, N. Y., a corporation of New Jersey No Drawing. Application April 14, 1939,

- Serial No. 267,923

4 Claims.

The invention herein described and claimed relates to storage batteries of the lead-acid type, particularly having reference to the use in such types-of storage batteries of an improved separator manufactured according to the method herein described. The objects of the invention include, among others, the manufacture of an improved type of storage battery separator as well as the use of such improved separator in storage batteries of the lead-acid type, thereby to impart to the storage battery an improved discharge capacity and a longer life. The novel separators of the present invention are characterized in that they contain as an integral part thereof, an added active organic ligneous compound.

By the term organic ligneous compound as used in the description of the present invention, are meant all those organic materials of extremely complex chemical nature which are present in all forms of vegetable matter other than the cellulose, fats, waxes, resins, wood acids and salts of wood acids, and embraces the derivatives of such complex chemical materials, addition and decomposition products thereof. It is not possible to state what is the true chemical nature of lignin or of organic ligneous materials; chemical science has not yet determined the structure thereof. It is known, however, that when substances of vegetable origin are suitably treated with acidic materials such as calcium acid sulfite, alkalies or some organic solvents, such as dioxane there are obtained solutions containing among other things some of the ligneous materials originally present in the vegetable substances. Separated from the naturally occurring fats, waxes, resins, wood acids and salts of wood acids also present in the vegetable substance the organic ligneous materials, "I have found, possess properties which are conducive to better battery performance when added to separators, and I have designated such ligneous compounds in the description of the present invention and in the appended claims as active organic ligneous materials. Such a designation will serve to distinguish over those unextracted inactive ligneous compounds which are originally found and which remain, after treatment, in the structure of the wood. Inasmuch as these organic ligneous compounds are present in all forms of vegetable substances, the particular type of vegetable substance from which the active organic ligneous compound is derived is of no consequence in the practice of the present invention. Wood is a very convenient source for obtaining these active organic ligneous compounds, as is also straw, hemp, jute, corn-cobs, bagasse, humus, peat moss, etc. The so-called waste sulfite liquors obtained from the manufacture of paper or solutions resulting from caustic alkali or inorganic acid processes for treating wood or wood pulp, are a readily available source of organic ligneous compounds,

. useful in the practice of the invention. On the Whole, the sources from which active organic ligneous materials may be derived are well understood by those skilled in the art.

It has been known, prior to our invention, that if lignin and ligneous materials be incorporated into the negative plate of a lead-acid ty-pe storage battery, certain desirable eifects, in the nature of greater discharge capacity, were imparted to the storage battery. In the manufacture ofstorage battery separators the most commonly employed material used up to now has been wood. A separator fashioned from wood is treated, for example, with caustic alkali solutions, to remove from the wood the naturally present fats, waxes, resins, wood acids, salts of wood acids and some of the ligneous materials because the art had observed that such compounds as present in the wood in their original states are subject to hydrolysis in the storage battery to the detriment thereof. The so-treated separator, as employed by the prior art, was therefore, substantially free of any fats, waxes, resins, wood acids, salts of Wood acids, all of which are regarded as detrimental to storage batteries of the lead-acid type.

As noted above, in the treatment of wood separators with caustic soda solution, there is removed in addition to the fats, waxes, resins, wood acids, and thelike some of the ligneous material which is uncombined or loosely combined in the wood structure, possibly 23'% of the total ligneous substance content. A large proportion of this ligneous substance present in the wood is not affected by the caustic soda treatment, probably because it is firmly combined with the cellulose structure of the wood. At any rate, this so called hemicellulose ligneous organic combination apparently is ineffective in producing improved separators, and I have found it to be necessary to add the so called active ligneous material to the treated wood separators in order to impart to a storage battery improved life and low'temperature capacity.

Therefore, it should be understood that untreatedwood separators do not. exhibit the im proved properties of my treated separators, and

that the ligneous material originally available in the wood is not in the proper active form to produce the desired improvements. Furthermore, it has been found desirable, in thepractice of my invention, to efiect a uniform distribution of the active ligneous compounds over the surfaces of the separators with sufficient penetration to anchor the products when the organic is set .by the acid fixing treatment.

Thus I have now found thatif active organic ligneous compounds prepared according to the present invention are made a part of a battery compounds.

, is preferably separator, for instance, by impregnating a wooden separator of the prior art or by compounding these materials into a composition separator, the resulting separator has the unusual property of imparting greater discharge capacity and a longer life to the storage battery.

The manufacture of a wood separator for use in a storage battery according to the methods of the present \invention will now be further described for illustrative purposes, it being under stood that my invention is not limited to wooden separators but embraces all types of battery separators which contain as an integral part thereof added active organic ligneous compounds.

A preformed wood separator f the present commercial type, i. e., one which has been subjected to a treatment, e. g., caustic soda treatment, to remove organic fats, waxes, resins, wood acids, salts of wood acids and some or the readily soluble organic ligneous compounds, etc., is immersed in a solution of active organic ligneous The solution of activ organic ligneous compound may be obtained by any of the suitable means above described. For purpose of this illustration, the active organic ligneous solution may be derived from a waste sulfite liquor or a caustic alkali liquor obtained from papermaking processes, Preferably the solution containing the separator is heated to hasten absorption of the active organic ligneous compounds by the separator. Generally speaking, the higher th heat, the greater will be the rate of absorption, but the temperature should preferably be not higher than that of boiling water. Thus, temperatures between 70 and 212 F. are very suitable tothe practice of the invention. The processing may be carried out at atmospheric pressure, if desired, the impregnation may be carried out under pressure in an autoclave.

The concentration or the activ organic ligneous compound solution is not critical; for example, waste sulflte liquors or caustic alkali liquors treated in known manner to render them substantially non-frothing and non-sulfating obtained from paper making processe and containing the usual -12 percent of solids may be used. impregnation should be carried out until, as determined by test, the separator has absorbed a desired amount of active organic ligneous material. Only a small amount of absorbed active organic ligneous material gives the improved results of the invention. Amounts between 0.01 percent and 5 percent or the weight of the separator, preferably between 0.25 and.2.0 percent constitute a practical range within the scope of the invention, As will be appreciated the solution of organic ligneous compound should be as free as possible of objectionable organic or inorganic salts which might interfere .with the proper functioning of the ligneous compound or separator.

After the separator has been impregnated as described, the active organic ligneous compound fixed in the separator by treatment with a suitable "fixing agent. Among those best suited for this process are solutions sorbed by the separator. So also do solutions of salts, the electro-positive element of which precipitates ligneous compounds from their solutions. The fixing treatment may also be advantageously carried out at an elevated temperature, say, between 70 and 212 F. Furthermore, the fixing treatment may not necessarily follow the impregnation and the impregnated separators maybe dried and stored for some time before treatment with the fixing agent, depending upon the components of the separator. After washing and drying, the so-treated separator is ready for use in a storage battery. The fixing treatment is especially recommended when the separator after impregnation with the active organic ligneous compound is stored prior to use or is separately prepared by the separator manufacturer and shipped to the storag battery maker; However, when separators are prepared in the, storage battery plant and directly used in the battery the fixing treatment may be dispensed with, but should the active organic ligneous compound exhibit a tendency to bleed out of the separator into the weak acid electrolyte, which may be encountered when the plate-forming acid is absorbed by the unformed plates, a

fixing treatment should be employed. The separator thus manufactured will have the active organic ligneous compound evenly deposited on the surface and uniformly distributed throughout the pores thereof,

' In connection with the foregoing, it should be pointed out that the impregnating solution of active organic ligneous compound may be either an aqueous solution, acid, alkali or organic solvent solution.

In the manufacture of composition separators, for example, those made by pressure operations, the active organic ligneous material compounds in the form of dry powder may be mixed directly with the materials from which the separator is formed and the separator fabricated in the usual manner.

Bagasse, pressed fiber separators, spun glass,- or glass-fibre separators which are adaptable to be impregnated, or to which th organic solution may adhere, may be subjected to an impregnation treatment substantially the same as that described in connection with wood separators.

Now, in order that those skilled in the art may appreciate the advantages of this invention, the

following specific embodiments are given, but

only for illustrative purposes: Example 1 A batch of the regular wood separatorsof commerce, that is, those having been treated to remove fats, waxes, resins, wood acids, salts of of sulfuric acid of a strength which may vary litharge, also exert a fixing wood acids, and some of the ligneous materials, were digested at atmospheric pressure for one hour at a'temperature of about F. in an active organic ligneous compound in a 5 percent sulfuric acid solution, having aspeciflc gravity of about 1.063 and containing grams of active organic ligneous compounds in 800 cc. thereof. After this digestion treatment the separators were immersed in a sulfuric acid solution of about 25 percent strength at about 120 F. for 30 minutes in order to fix the active organic ligneous compounds into the pores of the separator. After the fixing treatment, the separators were washed.

Examplez A second batch or wood separators, the same to the identical treatment as described in Exampl 1 with the exception that the solution of active organic ligneous compounds was a caustic soda solution, containing 160 grams active organic ligneous compound and 2 percent caustic soda in 800 cc.

Example 3 A batch of composition rubber separators was subjected to the same treatment as described in Example 1 Example 4 A batch of composition rubber separators was subjected to the same treatment as described in Example 2.

The separators obtained from these four examples, were made up into standard type leadacid storage batteries. These batteries were then subjected to a standard discharge test in comparison with other batteries made up with untreated wood separators from the same stock as were used for Examples 1 and 2, as well as batteries made up with untreated composition rubber separators from the same stock which were used for Examples 3 and 4. The technique on the tests was as follows:

The batteries undergoing automatic life tests were subjected to a discharge of 300 amperes at F. and a cut-out of one volt per cell or 3 volts for the entire battery. When the battery was completely discharged, it was fully charged and again discharged under the same test conditions,

'the discharge and charge being considered as i Table 1 Duration of discharge portion of cycle- No. of seconds cycles Treated Untreated Wood separators 253 240 125 Composition separators 253 200 80 N. B. No appreciable difference was noted in the results obtained with separators prepared according to Examples 1 and 3 and those prepared according to Examples 2 and 4. Hence, the figures given above are the average obtained. It is further to be noted that the negative plates of all batteries employed in the tests contain organic expanders.

The improved result of my invention is most pronounced at the period when it is most needed,

namely, after numerous cycles of discharge and charge and particularly effective under the most severe operating conditions, viz., cold weather. Furthermore, the improved result is not dependent upon nor associated with the presence of an organic expander in the negative plate.

The improvement of the present invention is obtained regardless of whether the negative plate of the battery contains an organic expander or not. Where expanders are used in the negative plates in conjunction with the present invention, it appears that the effect of the improved separator makes itself felt most prominently about the time the effect of the organic expanders of the negative plate begin to be dissipated.

When the novel separators of the present invention are incorporated into storage batteries of the lead-acid type, batteries are obtained which possess greater discharge output capacity and longer life especially at low temperatures which, over 300-350 cycle life test period is seldom less than 40 percent greater than a similar battery containing the separators of the prior art and in many cases is as much as 100 or more percent greater.

What I claim is:

1. Method of manufacturing an improved, porous storage battery separator which comprises immersing a pre-fabricated storage battery separator in a solution of active organic ligneous compound until a small amount of active organic ligneous compound is absorbed by the separator.

2. Method of manufacturing an improved, porous storage battery separator which comprises immersing a pre-fabricated storage battery separator in a solution of active organic ligneous compound and maintaining the immersion at temperatures between about and about 212 F. until a small amount of active organic ligneous compound is absorbed by the separator.

3. Method of manufacturing an improved, porous storage battery separator which comprises immersing a pre-fabricated storage battery separator in a solution of active organic ligneous compound until a small amount of active organic ligneous compound is absorbed by the separator, withdrawing the separator and treating it with a non-oxidizing fixing agent.

4.' Method of manufacturing an improved, porous storage battery separator which com prises immersing a pre-fabricated storage battery separator in a solution of active organic ligneous compound until a small amount of active organic ligneous compound is absorbed by the separator, withdrawing the separator and treating it with a solution of a compound selected from the groupconsisting of non-oxidizing mineral acids, ionizable salts, and lead compounds.

BRUNO H. SCHUBERT.