SK140893A3 - Sheet produced by a wet process and application thereof - Google Patents

Abstract

Separator for recombination batteries contains a sheet produced by a wet process to create a continuous sheet structure, which contains a blend of glass fibres and fibres based on at least two synthetic substances, whilst the fibres are joined together on the surface. Synthetic fibres are made in the form of substance combination, constituting a three-dimensional network by creating a sheet and weldability of the sheet, whilst the synthetic fibres are either in the form of the blend of at least two kinds of fibres with different melting temperatures so that the first kind of fibres is created by the first synthetic substance, which softens during the production of the sheet, and the second kind of fibres created by second synthetic substance, which is melted during the welding of the sheet, or in the form of composite fibres, made of the first synthetic substance, which softens during the production of the sheet, and of the second synthetic substance, which is melted during the welding of the sheet.

Description

A NEW PLATFORM OBTAINED BY A WET PROCESS AND ITS USE

Technical field

The present invention relates to a novel sheet-like sheet formed by a wet process and to its use in particular as a separator for recombinant batteries.

BACKGROUND OF THE INVENTION

Compact portable electrolytic cells or batteries are well known comprising metal plates spaced apart and connected in series. An important factor in the development of such batteries is the use of thin porous separators placed between alternating positive and negative plates. The first function of these separators is to prevent metal lines between the plates to avoid short connections. At the same time, the separators must allow the electrolyte solution to pass freely to allow ion exchange between the plates.

for commercially available rubber batteries, sheet formations of molten polyolefin foils. are mainly described in patent applications

Wood based microporous cellulose fiber separators or such battery separators have been produced in U.S. Pat. 2,793,398, 3,890,184, 4,024,323,

113,927, 3,753,784, 3,694,265, 3,773,590,

340,100, 3,055,966, 3,205,098 and 2,978,529.

055 711, 3 351 495

Recently, maintenance-free batteries have been developed which pose particular problems in the production of separators. Maintenance-free batteries are sealed batteries that do not require water to be added during battery life. For many years cellulose fiber impregnated or aldehyde-treated separators have been produced. Such separators are described in U.S. Pat. However, these separators have the disadvantage of allowing gas losses and have therefore been abandoned for sealed batteries.

U.S. Pat. TEXON 4,359,511, 4,363,856, 4,529,677, and 4,618,401 disclose separators for maintenance-free batteries, which are formed by impermeable sealed shells on at least three sides to prevent the formation of metal salt bridges between the electrodes. These battery separators must have sufficient porosity to cause ion exchange, although the pores of the separators must at the same time be sufficiently small to prevent the migration of metal ions and thus the formation of a battery-shorting bridge. These lead and acid battery separators must also be resistant to the chemical effects of acids due to the strongly acidic environment present inside the batteries.

TEXON patents disclose such separators that can be bent and heat sealed along their edges. These separators consist of 5 to 20 masses. % of a polyolefin fiber slurry, from 2 to 15% by weight. polyester fibers, from 0 to 20 wt. % of glass fibers, from 40 to 75% by weight. fillers and 7 to 20 wt. % of crosslinkable binders. The polyester fibers have a length of 0.7 to 2.1 cm. These separators contain a number of components and are heat sealable.

U.S. Pat. No. 4,216,281 discloses battery separators that can be sealed by either heat or ultrasound. These separators consist of 30 to 70 masses. 15 to 65 wt. % of silica fillers and 1 to 35% of long fibers, which may be polyester. These polyester fibers have a length of 0.7 to 2.6 cm. Ion reagents are added to prepare the sheets on the paper machine.

The main disadvantage of separators for maintenance-free batteries made up of most polyolefin fibers is that they do not allow recombination of oxygen and hydrogen. It is therefore necessary to add water.

Recombinant batteries described in U.S. Pat. No. 3,362,861 and 3,159,508. These batteries are such that they allow recombination of oxygen and hydrogen formed during the electrolyte reaction.

Separators for recombinant batteries are also known which consist of glass fibers and polypropylene fibers.

U.S. Pat. No. 4,465,748 discloses recombination battery separators containing 5 to 35 masses. % of fibers having a diameter of less than 1 micrometer. The document also describes a glass fiber sheet having a length not exceeding 5 mm.

U.S. Pat. No. 4,216,280, recombinant battery separators are disclosed which consist of a glass fiber sheet containing 50 to 95% by weight. % of glass fibers having a diameter of less than 1 micrometer and 50 to 5% of glass fibers having a diameter of greater than 5 micrometers and preferably more than 10 micrometers. Such separators resist the electrolyte formed by the sulfuric acid solution, holding the sulfuric acid solution therein adapted as a sponge, allowing the battery to slide in all directions. Furthermore, they allow the recombination of hydrogen and oxygen, eliminating the need for water replenishment. These battery separators have the disadvantage of being expensive and used only for batteries for the telecommunications or IT industry. However, there is a need to provide battery separators that are less expensive and thus useful in the automotive industry.

U.S. Pat. No. 4,373,015 discloses a recombinant battery comprising a separator formed by a mat of short polyester fibers having a diameter of 1 to 6 microns. Such a fiber mat has a thickness of 0.3 mm weight per square meter of 50 g / m ² , a porosity of 90%, an electrolyte absorption of 100 to 200%. However, this fiber mat must be subjected to the following treatment. In particular, it must undergo a consolidation treatment to avoid pilling. This treatment consists in heating one area of the mat to partially melt the fibers while not destroying the porosity of the surface but only reducing it. Obviously, such processing increases the cost of manufacturing the battery separator. Moreover, its implementation is delicate. To reduce the pilling of the separator, especially in the vicinity of the positive battery plates, calendering is performed. The fiber mat must be treated with wetting agents to reduce the electrical resistance of the separator. The fiber mat is treated with, for example, alkylarylsulfonates or quaternary chlorine ammonium compounds.

PCT Patent Application WO 88/03710 discloses a recombinant battery separator consisting of a sheet comprising first fibers which are insensitive to an aqueous electrolyte and which imparts an electrolyte absorption of more than 90% to the sheet and second fibers conferring an electrolyte absorption of less than 80% to the sheet. The first fibers are glass fibers and the second fibers are hydrophobic to the electrolyte, for example, polyolefin fibers, i. polyethylene or polypropylene fibers.

Such a separator provides good results. However, it does not allow high frequency welding.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the aforementioned drawbacks.

One object of the invention is to provide a sheet-like structure for a battery separator that can be welded by high-frequency or ultrasonic welding. High-frequency or ultrasonic welding is desirable because it makes it possible to obtain solid and durable welds, while hot-arc welding with a disc electrode is much more brittle. In order to increase the life of the batteries, their plates are required to be placed in pockets created by stable welding and withstandable mechanical stresses to which they may be subjected in the manufacture of the battery or in its use.

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It is a further object of the invention to provide a sheet formation for a battery separator that does not need further processing to improve its physical properties and especially its internal cohesion. Yet another object of the invention is to provide a panel for a battery separator that does not need, for improving its electrical resistance, the introduction of chemical products in the manufacture of the panel. It is a further object of the present invention to provide a sheet which is compressible. Finally, it is an object of the invention to provide a separator sheet having a very high absorption of sulfuric acid.

For this purpose, the invention provides a wet-formed sheet formed by a mixture of glass fibers and at least one kind of synthetic fibers, the synthetic fibers providing both a three-dimensional mesh for forming the sheet and a weldability of the sheet.

For example, the synthetic fibers may consist of a mixture of at least two types of fibers having different melting points such that the first type of fibers is a first synthetic mass that softens when making a sheet and the second type of fibers is a second synthetic mass that melts when welding a sheet. department.

Preferably, the synthetic fibers are composite fibers formed from a first synthetic mass that softens in the manufacture of a sheet and a second synthetic mass that melts when welding the sheet.

More specifically, it is preferred that the first synthetic material has a softening point of from 100 to 140 ° C and the second synthetic material has a softening point of greater than 150 ° C.

According to a preferred embodiment of the invention, the first synthetic mass is a regular polyester, in particular polyethylene terephthalate and the second synthetic mass is a copolyester with a non-crystalline structure.

Preferably, the synthetic fibers comprise a sheath of the first synthetic material and a core of the second synthetic material.

The synthetic fibers may be microfibers having a diameter of less than 16 microns.

The sheet according to the invention is preferably comprised of 10 to 90% glass fibers and 90 to 10% synthetic fibers.

According to an embodiment of the invention, the glass fibers are composed of a mixture of fibers with a diameter of less than 3.5 micrometers and chopped yarns of 6 to 8 mm in length.

DETAILED DESCRIPTION OF THE INVENTION

The invention is explained in more detail in the following description by means of non-limiting examples.

Example 1

The following fiber mixture is suspended in water containing sulfuric acid to achieve a pH of about 3:

% of synthetic fibers containing a copolyester core and polyester sheath manufactured by the Japanese company KURARAY and sold under the designation SOFIT N 720,% of glass fibers consisting of 20 parts of fibers 206 and 80 parts of fibers 210X, and% of glass fibers with a length of 6 to 8 mm.

The fibers 206 and 210X are trademarks of MANVILLE. They consist of acid-resistant borosilicate glass.

The aqueous suspension thus obtained is diluted and introduced into the headbox of a paper machine to obtain a sheet-like sheet.

The sheet-like sheet obtained is three-dimensional, i. j. the polyester fibers in their coating, which melted by the effect of heat when passing through the sheet sheet upon drying, formed interfiber bonds. The surface formation is deflected, i. j. has a considerable thickness and is not easy to squeeze. The sheet has good dimensional stability and good mechanical stability. Moreover, its internal cohesion is increased due to the surface melting of the synthetic fibers.

The properties of the sheet have the following nominal values:

- weight per square meter 167

- thickness in millimeters (under a pressure of 10,3 kPa) 1,0

- density: 0,167

- tensile strength (according to NFQ03-004) * in machine direction in daN / 24.5 mm 3.33 * in transverse direction in daN / 24.5 mm 2.20

- tensile strength (according to NFQ03-004) * in machine direction in% 3,22 * in transverse direction in% 4,51

- capillary elevation (according to NFQ03-001) in sulfuric acid d = 1,27 at 20 ° C in machine direction, in 2 minutes, in mm 68

- adsorption of sulfuric acid (d = 1,27) at 20 ºC, in% 1000

porometric volume in

- pore diameters in% (according to ASTM F 316-86) in microns * Mini * Maxi * MFP

- electrical resistance (sulfuric acid, d = 1,280 at 26,7 ° C) n in ohms.cm

93.37

4.04 22.95

7.12

0,038

The absorption of sulfuric acid is measured as follows: Two circular test pieces with a diameter of 8 cm are taken and weighed. The test piece is immersed vertically in a beaker containing one liter of sulfuric acid at a density of 1,27 at 20 ° C. After a few seconds, the test piece is removed vertically to allow the bubbles to be released. Then immerse the test specimen vertically in the beaker for one minute. The test specimen is removed, taking care to allow it to drip above the bath. Dripping takes 45 seconds. Collect the droplet formed at the bottom of the specimen using a glass rod and reweigh.

The absorbency is expressed in% and is calculated according to the formula:

(post-impregnation mass: pre-impregnation mass) x 100.

The electrical resistance is measured as follows:

The material used is as follows:

- Altuglas beaker containing 4 lead cadmium lead electrodes for separator sliding (current passage area about 2,56 cm ² , ie 10 inch ² )

- DC generator 10 amps

- temperature control material

- sulfuric acid, density 1,28 at 26,7 ° C

The test specimen shall be cut out with a width of 140 mm and a height of 160 mm. The amperage is set to 10 amps between the two lead electrodes. The voltage in vacuum U _Q between the cadmium electrodes shall be recorded. Three separators are measured and the diameter is determined.

Results are given in ohms.cm ² [(U ^ -U °): 10 A] x 63.6 = resistance in ohms, cm ²

A rectangular sheet is cut, folded in half and welded by high frequency or ultrasonic welding on two lateral sides to form a pocket, inserting the front plate before or after welding. The weld is stable.

Example 2

A sheet according to Example 1 is produced, but 40 parts of glass fibers 206 and 60 parts of glass fibers 210X are used.

A sheet-like sheet is obtained whose physical properties and nominal values are as follows:

- weight per square meter 167

- thickness in millimeters (pressure 10,3 kPa) 1,0 density:

0,167

- tensile strength (according to NFQ03-004) * in machine direction in daN / 24,5 mm 3,8 * in transverse direction in daN / 24,5 mm 3,0

- tensile strength (according to NFQ03-004) * in machine direction in% 3,5 * in transverse direction in% 5,0

- capillary elevation (according to NFQ03-001) in sulfuric acid d = 1.27 at 20 ° C in machine direction, in 2 minutes, in mm 66

- adsorption of sulfuric acid (d = 1,27) at 20 ° C, in% 1200

- Porometric volume in% 93.37

- pore diameters in%

(according to standard ASTM F 316-86) in microns * Mini 4.00 4.00 * Maxi 15.50 15.50 * MFP 6.00 6.00 - electric resistance

(sulfuric acid, d = 1,280 at 26.7 ° C) in ohms cm ² 0.038

The rectangle is cut in the same way, the sides are bent and the high-frequency weld is welded. The weld is stable.

lateral? 4I / 0Y- 9i

Spare side

Claims (10)

A wet-formed sheet usable as a battery separator, characterized in that it consists of a mixture of glass fibers and at least one type of synthetic fibers, said synthetic fibers providing both a three-dimensional mesh for forming the sheet and a weldability of the sheet. The sheet according to claim 1, characterized in that the synthetic fibers consist of a mixture of at least two types of fibers having different melting points such that the first type of fibers is a first synthetic mass which softens in the manufacture of the sheet and the second type of fibers is formed by a second synthetic mass which melts when welding the sheet. The sheet according to claim 1, characterized in that the synthetic fibers are composite fibers formed from a first synthetic material which softens in the manufacture of the sheet and from a second synthetic material which melts when welding the sheet. 4. The sheet according to claim 3, characterized in that the synthetic fibers comprise a first synthetic material shell and a second synthetic material core. A sheet according to any one of claims 2 to 4, characterized in that the first synthetic mass has a softening point of 100 to 140 ° C and the second synthetic mass has a softening point higher than 150 ° C. A sheet according to any one of claims 2 to 5, wherein the first synthetic mass is a regular polyester and the second synthetic mass is a copolyester with a non-crystalline structure. Spare side The sheet according to claim 6, characterized in that the regular polyester is polyethylene terephthalate. A sheet according to any one of claims 1 to 7, characterized in that the synthetic fibers are microfibers having a diameter of less than 16 microns. A sheet according to any one of claims 1 to 8, characterized in that it is comprised of 10 to 90% glass fibers and 90 to 10% synthetic fibers. A sheet according to any one of claims 1 to 9, characterized in that the glass fibers are formed from a mixture of fibers having a diameter of less than 3.5 microns and cut threads with a length of from 6 to 8 mm.