Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer – spacer or materials for use therewith
Reexamination Certificate
1999-12-21
2002-06-11
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer, spacer or materials for use therewith
C429S252000
Reexamination Certificate
active
06403264
ABSTRACT:
BACKGROUND OF THE INVENTION
Lead/sulphuric acid-accumulators (for the sake of brevity referred to below as lead accumulators) contain to an over increasing extent separators made from filled poly-olefins. These separators are microporous separators, the composition and manufacture of which is known from the prior art (see, for example, DE-PS 1267 423, DE-PS 1298 712, DE-AS 1496 123, 35 40 718, DE-PS 36 17 318, DE-OS 30 04 659, GB-A 2, 027, 637, U.S. Pat. No. 3,351,495, U.S. Pat. No. 4, 024, 323 and U.S. Pat. No. 4, 237, 083). In contrast to separators based on impregnated cellulose paper, PVC or phenol-formaldehyde-resins, separators made from filled poly-olefins offer various advantages. On the one hand as a result of their favorable range of properties, the life duration and performance of lead accumulators can be improved, and on the other hand there are also advantages in the manufacture of the accumulator. The high flexibility of the separators made from filled poly-olefins allows fully automatic enveloping of lead plates and final sealing of the side edges, with result that the lead plates are protected in a separator pocket, closed on three sides.
However, in the use of separators made from filled poly-olefins in lead accumulators undesired processes are also observed. Through the interaction of the applied current, the constituents of the lead plates, the constituents of the battery acid and the constituents of the filled poly-olefin. separators, substances or substance mixtures form in the lead accumulator, which as a result of their low specific weight rise to the surface of the battery acid and there form mostly coloured and often also adhesive agglomerates, which tend to be deposited on the contact surfaces between the accumulator acid and the accumulator constituents, for example on the housing. Gases released in the charging process rise as bubbles in the acid, bursting on the surface of the acid thereby throwing acid and deposits upwards, which results in the cover, the cover opening, the cover-fastening possibly placed on it and the outside of the accumulator housing being covered with such deposits.
Housings for lead accumulators consist, for example, of polypropylene, methacrylate or polystyrene and are therefore transparent or totally clear. Coloured deposits forming when the lead Accumulator is in use deposit themselves on the inside of the containers and are therefore visible from the outside. As the deposits themselves are not transparent, an exact assessment of the acid level in the lead accumulator is prevented, thereby making the regular inspection and adjustment of the acid level in the accumulator more difficult. If insufficient water is added, the concentration of acid increases. At the same time the level of electrolyte can possibly sink so far that the lead plates partly protrude out of the acid and dry out.
Lead accumulators which, for example, are used for driving vehicles, are often fitted with a valve system for automatic water-addition. These lead accumulators are regularly connected to water reserve tank via valve system. When in proper working order the valve system ensures that a certain level of liquid is maintained in the lead accumulator. However, if this type of lead accumulator contains separators made of filled poly-olefins, then as described above, deposits form which can cause the water-addition system to be incapable of functioning. Consequently no water is added, and the acid level in the accumulator falls.
Many lead accumulators are fitted with gassing openings made from porous materials, which facilitate an unhindered escape of the gases formed in the accumulator and which prevent oxyhydrogen explosions by keeping sparks away from the gases. If this type of lead accumulator contains the filled poly-olefin separators described above, deposits can form when the lead accumulator is in use, as described, which can obstruct the de-gassing openings and thus make them impermeable to gases.
SUMMARY OF THE INVENTION
In view of the problems described above, the basis of the objective of the invention is to reduce the quantity of coloured, mostly dark and frequently adhesive deposits formed in lead accumulators with separators made from filled poly-olefins the use of a plasticizer with a low aromatic carbon content, low sulphur content and low polar constituent.
DETAILED DESCRIPTION OF THE INVENTION
To achieve this objective a lead/sulphuric acid accumulator with at least one separator made from filled poly-olefins is proposed which is characterized in that the separator contains as the plasticizer such as a process oil, having an aromatic carbon content, C
A
value, of ≦6%, a sulphur content ≦2000 ppm and a polar part of ≦1.0%.
In addition, the subject of the invention is a separator made from filled poly-olefin for lead/sulphuric acid accumulators, which is characterized in that it contains as the plasticizer preferably a process oil, with a C
A
value of ≦6%, a sulphur content ≦2000 ppm and a polar fraction of ≦1.0%.
Finally, the subject of the invention is a process for reducing the formation of coloured, mostly dark and frequently adhesive deposits in a lead/sulphuric acid accumulator with at least one separator made from filled poly-olefin, characterized in that separators are used in the accumulator which contain as the plasticizer a process oil with a C
A
value of ≦6%, a sulphur content ≦2000 ppm and a polar port of ≦1.0%.
It was surprisingly found that a decisive reduction in the aforementioned deposits can be achieved by the use of process oils as plasticizers for separators made from filled poly-olefin, if the oils have a C
A
value according to DIN 51378 (without sulphur correction) of ≦6%, a total sulphur content measurable according to DIN 51400 of ≦2000 ppm and a polar part according to ASTM D 20007-75 (polar compounds in % by weight) of ≦1.0%.
The mineral oils effective according to the invention are distinguised by the fact that they simultaneously meet the conditions C
A
≦6%, total sulphur content ≦2000 ppm and polar part ≦1.0%. By their nature these oils can be not only relatively naphthenic, or naphthenic but also paraffinic, with the viscosity/density constant serving for classification (Ullmans Encyclopaedie der technischen Chemie, Verlag Chemis 1981, 4the edition, Volume 20, page 616). Relatively naphthenic oils with a visosity/density constant of 0.820-0.849 are most preferred, while paraffinic oils are least preferred. In the latter the C
A
value should be greater than 1% but ≦6% and the sulphur content should be greater than 100 ppm and ≦2000 ppm. Aromatic oils basically do not fulfil the condition of C
A
≦6% and sulfur content ≦2000 ppm and are therefore not considered for use according to the invention.
The process oils effective according to the invention preferably have a C
A
value of ≦5%, and more preferred ≦3% and particularly ≦2%. The sulphur content of the process oils effective according to the invention is preferably ≦1000 ppm, more preferred ≦500 ppm and particularly ≦100 ppm. The polar part in the process oils effective according to the invention is preferably ≦0.7%, more preferred ≦0.5% and particularly ≦0.3%.
The plasticizer content of the separator according to the invention is within the normal boundaries. The plasticizer quantity based upon the finished separator weight is usually 1 to 40% by weight. Preferred plasticizer contents are 5 to 25% by weight and particularly 10 to 15% by weight. In addition to the highly refined process oils used according to the invention other usual plasticizers can also be used (see below).
Except for the process oils contained as plasticizers in the separators, the accumulator according the invention is a usual lead/sulphuric acid accumulator with conventional electrodes ie negative plates and positive plates and sulphuric acid as the electrolyte.
As already described in the prior art mentioned above, filled poly-olefin separators mainly contain polyethylene, where within the
Bünsch Hellmut
Ihmels Klaus Heinrich
Theubert Frank Otto
Chaney Carol
Daramic, Inc.
Nields & Lemack
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