GB2031300A - Method of producing battery separators - Google Patents

Abstract

Battery separators are provided with projections 33 on the main relatively flat surface 39 thereof formed from a web. The method of the invention overcomes or mitigates problems of damage to the web and use of organic solvents by a substantial departure from the conventional methods of forming projections as embossed ribs. In the invention, globules, e.g. of a plastics material, are fired at the web and made to stick to it, at least on cooling. Thus they are projected through a gas gap, normally an air gap, to provide substantially rounded projections. Any uneven-ness of the projections can be removed by passing the resultant web through thickness-sizing rollers. <IMAGE>

Description

SPECIFICATION Method of producing battery separators In the past it has been the practice to provide projections and ribs on battery separators by embossing the separator web or otherwise shaping the web by direct mechanical means.

Another method used in the past has been to extrude or otherwise apply projections or rib members directly to the surface of a battery separator web as for example is shown in U.S.

Patent 3,773,590. One patent illustrative of shaping a web of battery separator during manufacture to provide projections thereon is U.S.

Patent 3,798,294.

It is an object of the present invention to provide an inexpensive, expeditious method for providing spacing means on a battery separator web. Another object of the invention is to provide such spacing means with minimal damage to the battery separator web.

Another object of the present invention is to provide a method for providing spacing means on a battery separator web which does not require the use of solvents.

The invention provides a method for forming battery plate spacing means on battery separator web by forming globules remotely from the web and intermittently projecting the globules onto the web through a gas gap.

In preferred aspects the battery separator web is a porous polyethylene-containing sheet having two opposed faces. The web is continuously conveyed past a first station with one of its faces exposed. At this first station the web is isolated from engagement with the equipment. Shot globules of a polyethylene that melts between 200 and 4000F (93 and 2040C) and is free of tackifier are remotely formed and shot toward the exposed face of the web through an air gap and surface cooled in the air gap to improve integrity while retaining enough internal heat to fuse with the web and provide rounded configured projections extending from the web. The globules are impinged on the web and fused with the web forming substantially rounded configured projections. Thereafter the total thickness of the web with projections is tolerance sized.

In varient embodiments the composite web and projections are further processed to form the battery separator by cooling before tolerance sizing or a glass mat is engaged over the projections prior to cooling and then pressed into a secure engagement with the projections simultaneously with the tolerance control sizing. In this latter variation cooling follows tolerance control sizing.

A further aspect involves the product by process.

DRAWINGS Fig. 1 is a schematic perspective view of the apparatus employed in practising the method for providing a battery separator with remotely provided spacing means; Fig. 2 is a schematic vertical section view of the die of a solenoid gun, 11 A and 11 B; Fig. 3 is an enlarged view of the battery separator composite passing through the nip of rolls 35A and 35B; Fig. 4 is an enlarged view of another form of a composite battery separator; Fig. 5 is a view of a modification of the apparatus of Fig. 1 for production of the varient form of the battery separator shown in Fig. 4, only the downstream varient portion of the apparatus of Fig. 1 being illustrated; the upstream portion of the apparatus remaining identical.

The following is a more detailed description of preferred features of the invention and of apparatus for carrying out the invention. The apparatus includes standard equipment designed for application of adhesives to the flaps of corrugated paper board boxes when they are being set up. The shot-providing components of the equipment schematically represented in the drawing were obtained from The Aro Corporation; One Aro Center, Bryan, Ohio 43508, U.S.A.

Looking at Fig. 1a globule-forming, projecting and sizing system may be seen. Solenoid guns 11 A and 11 B are mounted stationarily above a moving back web 12 of battery separator material.

The web 12 is fed from a roll 13, and is taken up by powered roll 14. The solenoid guns 11 A and 11 B are fed molten polymer via feed hoses 1 5A and 15B. Manually operated valves 16A and 16B adjust the flow of the fluid polymer to each of the solenoid guns 1 1A and 1 1B respectively to provide an even output by each gun. Both hoses 15A and 15B connect to a hot melt console 17 which has a reservoir 1 8 (the door of which is shown) into which solid polymer is fed and melted. The console is available commercially, as are, in essential construction, the other individual parts of the apparatus.

An air driven pump 20 is provided to pump the polymer from the reservoir 1 8 and under air pressure, into the hoses 15A and 15B. A pressure regulating device 21, air filter 22 and air supply line 23 are shown.

The hoses 15A and 15B contain heating elements which maintain the polymer at the intended temperature during its transfer from the reservoir to the guns 11 A and 11 B which are also heated. The temperature of the hoses and guns is sensed and regulated to a substantially constant level as programmed by the hose controller console 24. The electrical and sensor control cables 25A and 25B connect the hose controller console to the respective hoses 1 5A and 15B.

Threaded pin-in socket junctions 26A and 26B permit easy disconnecting of the lines of the electrical and sensor cables 25A and 2sub.

The solenoid gun timing control console 27 is electrically connected to the solenoid guns 1 1A and 11 B via electric wires 28A, 28C and 28B, 28D respectively and complete the circuit via electric wires 29A and 29B respectively. Solenoid guns 11 A and 11 B have respective dies 30A and 30B each of which has four aligned orifices of veins 31 a, b, c, d, (Fig. 2) aligned to provide shots extending linearly in a plane perpendicular to and extending across the machine direction of the web 12. Positioning means 32A and 32B adjustably position the guns 11 A and 11 B.

As the solenoid guns are cycled by the solenoid gun control console 27 the respective solenoid guns 11 A and 11 B each ejects four small discontinuous streams of polymer dimensioned such that they individually impinge upon the web 12 providing generally circular projections 33.

Downstream of the solenoid guns 11 A and 11 B the web 12 is passed over a cooling roll 34 to assure a good setting of the melted polymer. Then the cooled web is passed between tolerance control rolls 35A and 35B which assure a final tolerance control sizing of the entire thickness of the battery separator from the back side 36 of the back web to the tip of the projections 33. The rolls 35A and 35B are powered and they set the speed of the web's movement. Take up roll 14 is a torque winder.

An alternative version of the apparatus adapted for application of a glass mat 40 directly adhered to the outer tips 37 of projections 33 on web 12 which has faces 36 and 39 as shown in Fig. 4 is also described. The apparatus would be the same as previously described except the downstream portion, which variation is shown in Fig. 5. The web 12 is fed directly from receipt of the projection members 33 to a set of rolls 41 and 42.

A glass mat 40 (a thin paste retaining fabric usually made of glass) is fed from roll 43 over the web 12 on tip of the projections 33 upstram of the nip of rolls 41 and 42. The rolls 41 and 42 therefore function to squeeze the glass mat 40 into the surface of the tips of the projections 33 while the projections are still molten enough to provide good interlock or adhesion with the glass mat. A cooling means 44, an air stream would be downstream of rolls 41 and 42 normally rather than being wound up, such battery separator assembly 45 would be cut to predetermined lengths and packaged for shipment in any conventional manner.

In a preferred method, the globule-forming material is a plastic. The globule-forming material is charged to the means 18 for rendering it molten. The preferred plastic is a polyethylene, most preferably a homopolymer of polyethylene having a Brookfield Viscosity of less than 10,000 more, preferably less than 5,000 cps at 1 400C.

This is in particular the preferred plastic for use with the preferred back webs which contain polyethylene, prnf,erably in amounts of at least 25% by weight of the webs total composition.

More generally preferred polymers are the olefin homopolymers of copolymers. Other polymers preferred in more limited applications as now foreseen are olefin copolymers containing carboxylic acid groups or polymers based on vinyl chloride. Other polymers are also suitable in given instances. The plastic is preferably one that is molten between 200 and 4000F (93 and 2040 C).

The plastic is preferably free of solvents because this eliminates the possibility of vapor being emitted that would pollute the environment.

By choosing a plastic from which to form the globules that is of the same chemical nature as the plastic in the back web it is possible to bring about a very good fusion of the globule and the back web without the necessity of the addition of tackifiers. In other words if some of the plastic in the back web is of the nature of the plastic in the globule the bonding will be by fusion rather than mere adhesion or mechanical intertwining, as presently understood. In any event this like material to like material bonding is defined for purposes of the present invention as fusion. By like materials it is meant the same polymer, though not usually of the same molecular weight.

For example a polyethylene in the back web would usually be of a higher molecular weight than the one in the globules. It is preferred that the temperature of the molten polymer be maintained below 4000F (2040 C) in the usual situation because this results in less damage of the typical back web materials. It is preferred that the melting points of the plastic to be used in the globule and the plastic in the back web be such that when the globule contacts the back web it will bring about the fusion of the two plastic members.

The battery separator sheet material or back web 12 is provided for receipt of the spacing members, projections 33. The preferred battery separator back web is fiberous synthetic pulp paper sheet containing polyethylene fibrils preferably in the preferred amount of at least 25%.

The most preferred battery separator back webs contain polyethylenes and preferably the polyethylenes have viscosity average molecular weights of 200,000 to 20,000,000 and becomes molten at a temperature between 1050C and 1400 C. The other preferred plastics to be used in the back webs are the same as those listed with respect to the globules. However the invention lends itself to preferred operation with other battery separator webs such as the microporous filled polyethylene sheets sold by W. R. Grace s Co. under the tradename DARAMIC. The invention however broadly lends itself to use with other battery separator back webs including even cellulosic back webs, including phenol formaldehyde impregnated cellulosic webs, as well as polyvinyl chloride and rubber battery separator back webs.

After the plastic has been melted it is ready to be supplied to the guns 11 A and 11 B by the pump 20 which is activated. Depending upon the width of the web and the number of projections to be supplied the appropriate die is chosen at initial setup and the cycle time both in total cycle time and in the length of the globule release time is chosen. In addition it is often necessary to adjust valve 16A and 16B at setup to keep the two guns uniform in the size globules shot out Such fine tuning is routine and need not necessarily be done with each run but is done as is necessary as is the usual practice with any process.

In the preferred procedure the back web is positioned as at 13 in Fig. 1 and passed under solenoid guns 1 A and 1 B as the means for applying globules of molten plastic. After the globule-forming equipment, including its supply elements that melt the polymer, has been appropriately placed in operation and sequenced, the back web conveyance is begun as shown by powering rolls 35A, 35B and 14 to withdraw the web from roll 13. The solenoid guns then begin cycling to intermittently release small pressurized amounts of molten plastic. The small amounts or globules of molten plastic are in short stream form. Thus the term "globule" as used here is not limited to masses of material that are rounded in shape. It is possible in this invention to fire several small squirts to form a single globule.

The globules are formed remote from the back web and as they are projected through the gas gap, preferably air gap, to the web they are surface-cooled to provide integrity while having the cooling controlled to retain enough internal heat to fuse with the web and thereby provide a fused, usually substantially rounded configuration on the surface of the web. If possible, the materials of the web and globule-forming plastic are chosen to provide a substantial degree of fusion upon impact. By "rounded configuration" it is not meant hemispherical but just that the projection is mounded up and reasonably even.

Thus the glob or projection rising from a flatappearing junction with the web as previously mentioned may be only adhesion-bonded if the globules and back web are of different materials.

In such instances it may even be necessary to add adhesion aids such as tackifiers. The globules aregenerally circular, but not usually perfectly circular, in outline sectional configuration where they engage the web. There is also normally some readily apparent variation in the size of the various globules, even to the naked eye, due to the impression of the equipment Their diameter may commonly vary by a factor of 2. However the general height distribution tends to be less than the diameter variation. The globules are preferably ejected in bursts of at least two globules, preferably by intermittent pressure-shouting as described, of at least two globules per burst. The drawing illustrates an operation in which there are four globules fired from each gun.

The length of the air gap between the die 30 and the back web 12 is adjusted at the time of initial set up commensurate with the spacing in the cross machine direction of the globules, and provides the desired cooling in the gap to provide integrity; the gap being small enough to control the retention of enough internal heat in the globule so that on impact the globule will fuse or otherwise bond with the web. The size of the globule is in part controlled by adjustment of the one part of the solenoid gun's cycle. By correctly controlling the cycling pressure and temperature, globules are provided that do not tend to present stringing from being too cool or tend to sink into the porous separator back web because they are too hot, providing an inferior product.

It should be observed that the equipment does not engage the web in the area where the globules are being projected onto the web. It has been found that when equipment does engage the web it tends to damage the web. Using direct application of extrudate onto the web also tends to bring about a distortion of the web, particularly in configuration, due to the almost inevitable differential shrinking or expansion of two joined elements as their temperatures change.

In the procedure shown in Fig. 1 the web 12 with the projections 33 thereon may be, it is estimated, engaged within several feet (about a metre) from the solenoid guns 11 A and 11 B by cooling roll 34 which may appropriately have a temperature of about 500F (180C). Of course cooling of the projections could be simply by an extended exposure to ambient conditions, blowing air on face 39 of the web or by other means.

Cooling by ambient conditions requires an elongated processing line with its obvious space disadvantage. The back of the web 36 is engaged by the roll 34 to avoid pushing the projections into the web before they are made more integrally sound. Such impingement into the web can increase distortion problems within the web.

While the overall thickness of the back web 12 and the projections 33 is usually relatively uniform, and therefore tolerance control sizing is not always essential it is a much preferred feature of the invention. It will be realized that the mechanical engagement of the projections and the web 12 between rolls 35A and 35B to provide a set tolerance thickness from the back 36 of the web to tips 37 of the projections has the disadvantage of mechanically damaging the battery separator and causing dimensional distortion. Thus the amount of engagement should be kept to the very minimum. In other words in the procedure there is a balance between damaging the composite of the projections and web and assuring a very specific thickness tolerance control in the composite battery separator.It will be understood that in use a number of separators are usually interleaved with a number of battery plates and the assembly is tightly fitted into a pre-sized battery cell compartment. Frequently up to 11 separators are present in a single cell and thus if the tolerance is not reasonably strict the possible randomly multiplying effect of thickness variations in given areas of a cell could result in significant mechanical pressure in one section of a cell while another section could be left too loose and damaged by vibration. Another advantage of aftersizing is that should the guns 11 A and 11 B get slightly out of adjustment causing slightly higher projections than intended the after-sizing can reduce the projections to the correct height. As already stated, this is a step of the process that must be carefully controlled in order to obtain a good balance between obtaining uniform thickness of the separator and limiting mechanical damage. Mechanical damage would even include the projections being pushed through the back web. This is a particular problem with weaker separator materials such as the preferred fibrous synthetic paper pulp webs which have lower structural integrity than many other kinds of web.

The sizing of the battery separator thickness between rolls 35A and 35B should be done before the projections are entirely hard, in other words while they are soft. They should not be molten, in order to prevent any adhesion or fouling of the rolls 35A and 35B by the material of the projections 33. The projections should be soft enough to conform without unnecessary damage to the back web.

The wind-up device 14 is of the torque type because as the roll gets larger it has a different wind-on surface speed. Thus the rolls 35A and 35B determine the speed at which the web passes through the process in the particular embodiment shown here. The rolls 35A and 35B are operated at ambient temperature. They could be operated at other, controlled, temperatures in appropriate circumstances.

In an alternative embodiment of the present invention it is possible to form an assembly of the back web and projections with a glass mat 40 (Fig. 4) by omitting the cooling roll 34 as shown in Fig. 5 and running a roll 43 of glass mat 40 onto the top of the projections over the web 12. The rolls 41 and 42 then squeeze the mat 40 into the upper surface of the projections as the composite passes through the set gap between rolls 41 and 42. Rolls 41 and 42 operate substantially the same as rolls 35A and 35B in Fig.

1. The glass mat prevents the adhesion of the upper tips 37 of the projections 33 to the roll 41 if the gap between the rolls 41 and 42 is properly adjusted so as to avoid gross passage of the material of projections 33 through the interstices of the glass mat. After passage through the gap between rolls 41 and 42 it is generally advisable to quickly harden the assembled composite battery separator 45 with a fluid means such as air as shown in 44 or alternatively water. Of course if water is used it must be dried off prior to finishing the separator. It can generally be anticipated that the battery separator 45 shown in Fig. 4 with the glass mat bonded therein would be chopped or cut to final separator size on the continuous line and then boxed for shipment. Of course the battery separator could be rolled up as described with relation to Fig. 1.Of course the battery separator of Fig. 1 could be chopped into sized separators rather than being rolled up.

The invention is further illustrated by the following Example.

EXAMPLE Turning now to the operation of the apparatus in forming a battery separator containing the spacing projections provided by the method of the present invention, a roll 5,000 feet long and 6.1 6 inches wide by 0.012 inch thick (1520 m. long and 15.6 cm. wide by 0.30 mm. thick) battery separator back web generally similar in character to the fibrous sheeting described in Auslegeschrift 2,509,823 that would have about 48% polyethylene synthetic woodpulp. The web was not of identical composition to those described in the Auslegeschrift but instead was made as follows.

A pulp was formed in a pulper by charging 1000 Ibs. (455 kg.) of water to the pulper followed by 37.6 Ibs. (17kg) of short fibred synthetic polyolefin pulp with average length of 1 mm. cross section area on the order of a few square microns and specific surface area on the order of 1 0m2/g. polyethylene fibres (PULPEX A product of Solvay s Cie). This was pulped for about 25 + 5 minutes. Then 36 Ibs. (16.4kg) of siliceous filler, amorphous silica (Hi Sil 233 product of PPG Industries) was added. The filler was wet down before addition to provide dust reduction.

After the silica was added the pulper was operated for an additional 5 or 10 minutes to mix well. Then 800 Ibs. (364 kg.) of additional water was added to aid in more complete mixing and to flush out the pulper.

The pulper contents were transferred to the chest of a laboratory rotoformer paper machine.

Then 6.4 Ibs. (2.9 kg.) of long fibres were added.

The long fibres were polyethylene terephthalate staple fibres 1.5 denier x 1/4" (0.63 cm.) supplied by Minifibers, Inc. Thereafter about 5500 Ibs.

(2500 kg.) of water was added. Next 1.6 Ibs. (0.73 kg.) of ground paper makers' alum (alum sulphate iron-free ground product of Du Pont) was added to adjust the pH to 4.5 to 5.5. After thorough mixing and dissolving of the alum the slurry was allowed to stand for about 1 hour. Then the aqueous slurry was transferred from the chest to a dilution box just upstream of the headbox. The rate of transfer by pumping was set to yield a web having a grammage (weight) of 120g/m2.

The mix was diluted with water in the dilution box to about 0.06 weight percent solids. A cationic copolymer containing acrylamide units (RETEN 21ova aproduct of Hercules Inc.) was metered in at the stuff gate, which is where the slurry from the chest flows into the mixing box, at a concentration of 0.04% in water at 800 ml/minute. An anionic copolymer containing acrylamide units (RETEN 421~ a product of Hercules, Inc.) was metered into the mix box about 3 feet (90 cm.) downstream of its 5 foot (1.5 m.) length at a concentration of 0.025% in water at 800 ml/minute. The ionic copolymers containing acrylamide functioned as retention aids causing the silica filler to become associated with the synthetic pulp present in the aqueous slurry.

This diluted mix was then transferred to the box where the web is formed on the rotoformer.

While on the rotoformer a lump breaker roll operated at 80 psi (5.6 kg./cm2) to smooth out the top surface of the web. The wire of the rotoformer travelled at a rate of 15 feet/minute (4.5 m./minute).

After leaving the rotoformer and while still resting on a moving belt the web was pressed by opposing hard rolls to reduce the caliper and pore size and increase the strength of the web. The caliper or thickness was reduced to 14 mils. (0.36 mm.).

The web was then transferred from the wire to an open mesh metal belt and passed through an oven where it was dried to a water content of about 10 Ibs. (4.5 kg.) of water for every 10 Ibs.

(4.5 kg.) of solid web. It was not necessary to heat the oven.

A polyethylene, AC homopolymer No. 9 manufactured by Allied Chemical Corporation was fed into the melt chamber reservoir 18 and melted at a temperature in the reservoir of approximately 2750F (1 350C). Small amounts of additional solid polyethylene were added to the reservoir as needed to keep the supply adequate for continuous operation. The hoses 15A and 15B and the guns 11 A and 11 B were maintained at about 3000F (1490C). The solenoid gun control 27 was regulated by timers to a total cycle time of approximately 0.2 seconds. The "on cycle" being determined by experimentation and the "off cycle" being of sufficient length to yield the desired projection spacing. Each die (Fig. 2) had four veins.

Each vein consists of a channel from the interior barrel of the die-head to a separate extrusion orifice. Each vein was positioned at an angle of 600 from the vein or veins adjacent to it The die was positioned 3/4 inch (19 mm.) above the back web. Each die was spaced 1 1/2 inch (38 mm.) in from its center to the edge of the back web and 3 inches apart center to center. The dies were 1/2 inch (12.5 mm.) in diameter. The air pressure on pump 20 was 3Q psi (2.1 kg./cm.2).

The web was withdrawn from roll 13 at a speed of travel of approximately 40 ft./min. (12 metres/min.) by driven rolls 35 A and 35 B and roll 14 downstream thereof. Roll 14 is à driven torque winder (wind-up roll). While in the contemplated preferred form the apparatus is as shown in Fig. 1, a slightly different apparatus was used for this Example. The equivalent of roll 34 was not watercooled but instead was spaced a greater distance away to allow additional air cooling. Roll 35 B was cooled to approximately 550F (130C) because it happened to have such a capability.The back 36 of the web 12 was draped across the very top of cooled roll 35 B and then extended out beyond this to allow additional air cooling and then passed over a roll equivalent in downstream position to roll 34 to bring about a directional change and then fed through the nip between rolls 35A and 35B in the reverse direction from that shown in Fig. 1. Roll 35A was also cooled to approximately 550F (1 30C). The web was then passed around roll 35A to reverse the direction back to wind-up roll 14.

The rolls 35A and 35B were set 0.041 inch (1.04 mm.) apart. The rows of projections 33 extended perpendicularly across the machine direction of the web and were 3/4 inch (19 mm.) apart on center. Each row contained 8 projections 3/4 inch (19 mm.) across on center. The projections in the row were spaced 3/1 6 inch (4.8 mm.) in from the edges of the web. The projections 33 appeared generally circular to the naked eye. A random measurement of the projections showed the thickness from the back face 36 of the web to the outer tip 37 of the projections 33 to vary between 0.041 inch (1.04 mm.) and 0.048 inch (1.22 mm.) and measured from about 0.01 inch (2.5 mm.) up to about 0.2 inch (5.1 mm.) in diameter.The projections appeared to the naked eye to be evenly rounded before engagement by sizing rolls 35A and 35B and slightly flattened after passage between rolls 35A and 35B provided a tolerance control step.

The measured thickness from the back face 36 to the tips 37 of the projections 33 after the tolerance control step was 0.042 inches + 0.002 inch (1.07 + 0.05 mm.).

There are many advantages to the present invention that have already been mentioned. Just a few of them should be emphasized. One is the fact that in the preferred operation of the invention strong, chemically and mechanically stable projections can be formed without the use of solvents or other possibly environmentally polluting materials. Another very important advantage of the present method is that it does not excessively abuse the back web when the projections are provided. Very surprisingly an acceptably uniform projection height can be provided on the back web under operable parameters. The start-up and shut-down capabilities of the manufacturing method are exceptionally short and favorable.

Claims (20)

1. A method for forming battery plate spacing means on battery separator web comprising forming globules remotely from the web and intermittently projecting said globules onto said web through a gas gap.

2. A method according-to Claim 1 wherein said globules are of solvent-free molten plastics material.

3. A method according to Claim 1 or 2 wherein said globules are of a molten plastics material having a melting point between 200 and 4000F (93 and 2040C) and said plastic is not heated above 4000F (2040 C).

4. A method according to Claim 1,2 or 3 wherein said globules are formed from molten plastic and are projected by intermittent releases of small pressurized amounts of said molten plastic, said molten plastic being surface-cooled in said gas gap to improve integrity while allowing it to retain enough internal heat to fuse with said web and thereby provide a fused projection on the surface of said web.

5. A method according to any preceding Claim, wherein said battery separator web is fibrous and contains at least some polyolefin and said globules comprise at least 25% of the same polyolefin.

6. A method according to any preceding Claim wherein said globules are free of tackifier and solvents.

7. A method according to any preceding Claim wherein the gas gap is an air gap.

8. A method according to any preceding Claim wherein said projecting is by pressure-shooting of globules in intermittent bursts of at least two globules.

9. A method according to Claim 7 wherein said globules are molten plastic, substantially completely free of materials that will be released to the atmosphere on hardening, said projection is by shooting said molten plastic globules through said air gap and impinging said globules on said web and said web is isolated from equipment engagement during said projection.

10. A method according to any preceding Claim, wherein said web is continuously conveyed from the location where said globules are projected onto it and passed between a pair of sizing rolls for adjusting the thickness of the projections.

11. A method according to Claim 8 wherein the projections are covered with a glass mat and the resulting assembly of glass mat and web is passed through the sizing rolls.

12. A method according to Claim 1 1 wherein, in the absence of the glass mat the material of the projections would adhere to the adjacent sizing roll and the interstitial structure of the glass mat and gap set between the rolls are adequate to prevent passage of the material of the projections through the mat to an extent which would cause said adhesion.

13. A method for forming battery plate spacing means on a porous battery separator web comprised of polyethylene and having two opposed faces comprising continuously conveying said web past a first station with a face of said web exposed; at said first station isolating said web from equipment engagement; remotely forming shot globules of polyethylene that melts between 200 and 4000F (93 and 2040 C) that is free of tackifier; shooting said globules toward said exposed face through an air gap and surfacecooling said globules in said air gap to provide integrity while retaining enough internal heat in said globules to on impact fuse said globules with said web and provide a substantially rounded configured projection from said web; impinging said globule on said web and fusing said globules with said web and forming substantially rounded configured projections on said web; and thereafter tolerance-sizing the total thickness of the web and projections.

14. A method according to Claim 12 wherein said web is continuously conveyed past a second station where its face opposite said projections is engaged by a cooling roll and said web is subsequently continuously conveying past a third station where said web and projections are provided with said tolerance-sizing by being engaged between a pair of sizing rolls.

15. A method according to Claim 13 wherein said web is continuously conveyed past a second station while said projections are still molten; at said second station the portions of said molten projections remote from said web are engaged with a glass mat, said web is continuously conveying with said glass mat engaged on said projections past a third station; and at said third station said glass mat, web and sandwiched projections are provided with said tolerance-sizing by being engaged between a pair of sizing rolls and simultaneously said glass mat is pressed into secure engagement with said projections; and said web is continuously conveyed past a fourth station where it is fluid-cooled.

16. A method for forming battery plate spacing means on a porous battery separator web having two opposed faces comprising continuously conveying said web past a first station with a face of said web exposed; remotely forming globules, shooting said globules toward said exposed face through an air gap and surface cooling said globules in said air gap to improve integrity while retaining enough internal heat in said globules to bond said globules with said web and provide a substantially rounded configured projection from said web; impinging said globule on said web and fusing said globules with said web and forming substantially rounded configured projections on said web; and thereafter tolerance-sizing the total thickness of the web and projections.

17. A method according to Claim 16 wherein said web is comprised of polyvinyl chloride and phenolformaldehyde resin impregnated cellulosic fibres.

18. A method according to Claim 1 substantially as hereinbefore described with reference to any one or more Figures of the accompanying drawings.

19. A method according to Claim 1 substantially as hereinbefore described with reference to the Example.

20. Battery separator web and battery separators having projections thereon formed by a method claimed in any preceding claim.