JPS6048862B2 - Battery separator made from non-woven mat - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nonwoven sheet battery separator comprising a plurality of laminated nonwoven mats of melt-bonded thermoplastic polymer fibers and a process for making the same.

The method of the present invention involves laminating one or more nonwoven mats made of thermoplastic polymer fibers and having high strip tensile strength to one or more nonwoven mats made of the same thermoplastic polymer fibers and having high tear resistance. including providing the nonwoven mat with high strip tensile strength and high tear resistance.

Lamination of nonwoven mats can be done by point welding or by the use of adhesives. A battery separator is disposed between the positive and negative plates of the battery. Referring to FIG. 1, a thermoplastic polymer is introduced into a pellet hopper 1 of an extruder 2.

The thermoplastic polymer is forced through the extruder towards the die head 3 by a drive device 4 . The die head 3 contains a heating plate in which the temperature can be controlled. The thermoplastic polymer is released into a gas stream from a row of die openings 6 in the die head 3 and is attenuated by the gas stream into fibers 7 which are collected on a moving collection device 8 such as a drum 9 and continuously A mat 10 is formed. The gas streams that subdivide the thermoplastic polymer are provided by gas jets 11 and 12 (shown clearly in Figure 2), respectively. Gas slots 11 and 12 are supplied with hot gas, preferably air, from gas lines 13 and 14, respectively. The method can be further understood by considering the die head 3, which is described in more detail in FIG.

The die head 3 has an upper die plate 15 and a lower tie plate 16.
Consists of. Thermoplastic poly. When the mer is pushed into the rear part of the die head 3 by the extruder 2, it is introduced into the rear part of the goo plates 15 and 16 through the inlet 17. The thermoplastic polymer then enters chamber 18 between upper and lower plates 15 and 16, respectively. There are 3 grooves 19 cut into the surface of the tie plate 16,
The groove 19 leads to the tie opening 6. Of course, the grooves may be cut in either the lower die plate 16 or the upper die plate 5, or in both plates 15 and 16. Furthermore, if a single plate is used instead of the upper and lower die plates, grooves are drilled to create the die openings 63. The upper gas cover plate 2U and the lower gas cover plate 21 are coupled to the upper die plate and the lower die plates 15 and 16, respectively, and have an upper air chamber 22 and a lower air chamber communicating with the gas slots 11 and 12, respectively. An air chamber 23 is provided. Heat 4 (gas is supplied to the inlet 24 of the upper gas cover plate 20 and the lower gas cover plate 2)
It is supplied from the inlet 25 of 1. Suitable baffling means (not shown) may be provided in both the upper air chamber 22 and the lower air chamber 23 in order to equalize the flow of air through the gas slots 11 and 12, respectively. The die head 3 includes heating means 5 for heating both the thermoplastic polymer and the air in the die head 3. The properties of nonwoven thermoplastic polymer mats produced by meltblowing methods vary considerably depending on the particular operating conditions used.

The properties of nonwoven thermoplastic polymer mats are largely influenced by the air flow rate used in the melt blowing process and the distance between the die opening of the die head and the winding device. These effects are significant when attempting to produce meltblown nonwoven mats with high strip tensile strength and high tear resistance. However, it has been found that both high strip tensile strength and high tear resistance cannot be obtained in a single meltblown, nonwoven thermoplastic polymer mat.
At the heart of the present invention is the recognition that in order to provide meltblown nonwoven thermoplastic polymer sheets with both high strip tensile strength and high tear resistance, they must be laminated together. In particular, the invention involves making a battery separator by laminating a meltblown nonwoven mat with high strip tensile strength to a meltblown nonwoven mat with high tear resistance. In the melt blowing method, when the flow rate of air is high and the amount of air relative to the thermoplastic polymer extruded from the die head is large (in the case of polypropylene, the weight ratio of air to the weight of the polymer is suitably about 140 or more, preferably 150, preferably 200 or more),
The thermoplastic polymer fibers in the nonwoven mat generally provide the mat with relatively high zero span tensile strength.

When the air flow rate is relatively high, the fibers are drawn and become very fine fibers as evidenced by their small diameter (1-10μ). One of the other operating variables in the meltblowing process that greatly influences the properties of the nonwoven thermoplastic polymer mat is the distance between the winding device and the die opening and die head. It is clear that when the collection device is between 2.5 and 15 α from the die opening, significant fiber self-bonding occurs as the fibers are deposited into the nonwoven mat. When the distance between the die opening and the collection device is greater than or equal to 15Crf1, some self-coupling still occurs, but the amount of '1 self-coupling decreases with distance. As used herein, the term "self-bonding" refers to the thermal bonding of one fiber to another fiber in a melt-blowing process in forming a nonwoven thermoplastic polymer mat. The strip tensile strength of thermoplastic polymer mats produced by melt blowing is highest when the degree of self-bonding is highest. This is because self-coupling decreases. This is because the mat will essentially contain tangled fibers and the strip tensile strength will be greatly reduced. Another factor in meltblown matt strip tensile strength is the tensile strength of the fiber itself. The tensile strength of the fibers in a meltblown nonwoven mat is determined by measuring the zero span tensile strength of the mat. The measurement utilizes the same general method used to obtain the strip tensile strength of the mat. The method for obtaining strip tensile strength and zero-span tensile strength is to use a drawing rate of 250%/min with the clamps separated at a distance of 5.08 cm when measuring strip tensile strength, and to use a drawing rate of 250%/min with the clamps separated at a distance of 5.08 cm when measuring strip tensile strength; Same as ASTM method D-828-60 except no separation. Both places. If the result is reported in meters, it is necessary to break the mat (g) divided by the width of the sample to obtain the value in g/? The operating variables used in the melt blowing process to obtain mats with high strip tensile strength will give these mats low tear resistance.

Correspondingly, if a nonwoven mat with high tear resistance is produced, the strip tensile strength of the mat will be low. A necessary condition for producing mats of high tear resistance is generally to position the winding device at a distance of 20 cm or more from the die opening so that substantial entanglement of the fibers occurs, much more than self-bonding. Furthermore, relatively large diameters, i.e. in the range 10-40μ, typically 15-2
Relatively low velocity airflow to obtain a 5μ fiber mat;
It is therefore desirable to operate at very low air flow rates relative to the polymer velocity (generally less than about 50 for polypropylene). Non-woven mats made of these relatively large diameter thermoplastic polymer fibers, collected as entangled fibers and containing some self-bonding, are
It has higher tear resistance than nonwoven mats made of relatively small diameter fibers intertwined with each other. Tear resistance of nonwoven mats is determined by a standard Elmendorf tear strength tester according to ASTM method D-689-62. When used in the laminate sheets of the present invention, the strip tensile strength of meltblown nonwoven mats is generally lower than desired, even if the zero span tensile strength of the mat is sufficiently high.

Accordingly, strip tensile strength is improved by treating the nonwoven mat with a fusing process. Fusing is accomplished by applying a spaced pattern of heat to the mat to melt various portions of the mat and fuse some of the fibers in the mat. Alternatively, fusing can be accomplished by generally fusing the fibers by applying a continuous heat pattern to the mat. The fusion method requires sufficient pressure to prevent shrinkage of the fibers in the nonwoven mat, as indicated by measuring the size of the mat before and after fusion, and recognized by no reduction in the zero-span tensile strength of the nonwoven mat. Can be applied. Referring to FIG. 3, a heated press 30 can be used in the fusing process to increase the strip tensile strength of the meltblown nonwoven mat.

The brace 30 includes a plate 31 and a plate 32. Plate 31 has a plurality of spaced protrusions 33 tipped with flat lands 34 spaced apart according to a pattern. The spacing of the protrusions 33, the entire surface of the flat lands 34, and the pattern of the protrusions 33 on the plate 31 partially point bond the fibers of the nonwoven mat. A suitable pattern is a rectangular linear or diagonal grid, but the spacing and pattern of the protrusions 33 can be very wide. A suitable spacing between the protrusions 33 is approximately 1.6 TWL to 6.4 TWL. Projection 3
The depth that 3 sinks into the nonwoven sheet can be controlled by placing spacers or shims between plates 31 and 32. The plate 32 is the protrusion 3 of the plate 31.
3, or a protrusion aligned with the protrusion of the plate 31 so as to contact the land 34 of the protrusion of the plate 31. To increase the strip tensile strength of non-woven mats, non-woven)
It is desirable that the protrusions 33 are deeply recessed into the woven mat. Plates 31 and 32 are each heated independently, and their temperatures need not be equal. In the non-woven mat fusing method, a spacer sheet is used between the plates 31 and 32 of the brace and the non-woven mat to prevent the non-woven mat from sticking to the plate during or after the fusing operation. is convenient.

Suitable spacer sheet materials are insulating materials such as tissue paper, regular paper, etc., thermally conductive materials such as aluminum foil, etc.

A thermally conductive spacer sheet is preferred because the additional heat enhances fiber fusing in the fusing process. For the continuous production of improved high strip tensile strength nonwoven mats,
Advantageously, the fusion process is carried out by calendering the non-woven mat under sufficient pressure to prevent shrinkage of the fibers of the non-woven mat, and under heating conditions for fiber-to-fiber fusion.

FIG. 3A shows Karen goo rolls 40 and 41 that can be used in place of brace 30. Calender roll 40 can also have protrusions with flat lands at the ends having a broadly shaped pattern, such as a diagonal grid (not shown). In calendering for fusing, a spacer sheet can also be used to prevent the nonwoven mat from sticking to the calender roll. According to the present invention, a nonwoven laminate battery separator is manufactured from at least one mat of thermoplastic polymer fibers having high strip tensile strength and at least one mat of first thermoplastic polymer fibers having high tear resistance; The cohesive laminated sheet has both high strip tensile strength and high tear resistance.

Lamination can be obtained by using adhesives or by spot welding methods. Lamination. Meltblown nonwoven mats with high strip tensile strength and meltblown nonwoven mats with high tear resistance each have properties in their nonwoven laminate sheets that are approximately proportional to the weight fraction of each mat. It is done to the extent that it contributes. It is preferred to use an adhesive to complete the lamination when a nonwoven laminate sheet with low delamination properties is desired. Suitable adhesives for laminating a meltblown nonwoven mat to another are contact cements such as nitrile, SBR or polyisobutylene rubber types. When using adhesives, the adhesive is usually applied to one side of one meltblown nonwoven mat, the other mat is placed in contact with the adhesive-coated side, and the mats are pressed together. do.

Of course, it is also possible to apply an adhesive to the surface of each meltblown nonwoven mat and bring the coated surfaces into contact with each other for lamination. After coating the nonwoven mats with an adhesive and bringing the mats into contact with each other, they can also be compressed by passing them through flat surface calender rolls to form the nonwoven laminate sheets of the present invention. Another method for laminating meltblown nonwoven mats to form the nonwoven laminate sheet of the present invention is to spot weld the mats.

In this respect, except that in the point welding method there are at least two mats: at least one meltblown nonwoven mat with high strip tensile strength and at least one other meltblown nonwoven mat with high tear resistance. The welding method is essentially the same as that for fusing a single mat. In FIG. 4, the nonwoven laminate sheet of the present invention is shown in two point welded mats: nonwoven mat A, which has high strip tensile strength, and another meltblown nonwoven mat, B, which has high tear resistance. . The spot welding method is accomplished by using a press or calender roll as shown in FIG. Lamination of the sheets is accomplished in point welding by fusing the fibers in each meltblown mat at the intermediate surfaces of the overlapping mats. Shims or spacers (not shown) may be used to allow the protrusions of the brace or calendar roll to recess to a depth that allows fusing of the fibers at the intermediate surface of the meltblown nonwoven mat. In the spot welding process, the meltblown nonwoven mat B with high tear resistance undergoes the most changes in its properties by heating to high temperatures.

Therefore, instead of being in contact with a flat press plate or calendar roll, the nonwoven mat B with high tear resistance is placed in contact with the projections of the press plate or calendar roll, and the nonwoven mat B with high tear resistance is placed in contact with the projections of the press plate or calendar roll with projections. Preferably, the operating temperature is lower than with flat press plates or calender rolls. A spacer sheet can also be used in the spot welding method. In this operation, the spacer sheet that prevents the nonwoven mat from sticking to the press plate or calender rolls may be of the same or different material. A thermally insulating material, such as paper or tissue paper, can therefore also be used in contact with the non-woven mat B, which has a high tear resistance, and a spacer between the non-woven mat A, which has a high strip tensile strength. The sheet can also be a thermally conductive material such as aluminum foil. These modifications are made simply in an effort to preserve the physical properties of the meltblown nonwoven mat at a high level in the lamination process. The invention is illustrated with a nonwoven mat formed from meltblown polypropylene fibers.

However, other thermoplastic polymer fibers can also be used in the present invention. Other polyolefins such as polyethylene, polyesters such as polymethyl methacrylate and polyethylene terephthalate, polyamides such as polyhexamethylene adipamide, polyomega-caproamide and polyhexamethylene sebaamide, polystyrene, etc. Other polymers such as polyvinyl, polytrifluorochloroethylene. The specific meltblown nonwoven mats used in the following examples illustrate the present invention and utilize meltblown polypropylene fiber nonwoven mats prepared according to the conditions set forth in Table I below. The melt blowing process used was that shown in Figures 1 and 2 with the specific operating conditions listed in Table I. The properties of certain nonwoven mats are listed in Table I in terms of basis weight, zero span tensile strength, and the uniformity of the mat with respect to zero span tensile strength expressed as the ratio of its normal to machine direction (CD/MD). Examples 1 to 15' (The laminated nonwoven sheet of the present invention will be explained with reference to the examples shown in Table 1 below.

The laminate sheet is prepared by laminating a meltblown nonwoven mat of polypropylene fibers with high strip tensile strength to a meltblown nonwoven mat of polypropylene fibers with high tear resistance. Lamination is carried out by point welding of mats (Examples 1 to 12) or by use of adhesives (Examples 13 to 15). Non-woven mats of polypropylene fibers with high strip tensile strength were spot welded (Examples 1 to 9) or calendered (Example 1) under the conditions described in Table 1.
0 to 15).

Spot welding or calendering is carried out on the nonwoven mats indicated in capital letters made under the conditions of Table I. The treated nonwoven mats for high strip tensile strength were laminated to meltblown nonwoven mats with high tear resistance (mats P and Q in Table I). The properties of the obtained laminated nonwoven sheet are also listed in Table 3. In Examples 1-9, the strip tensile strength of the melt-blown nonwoven mats (Mat A-D in Table I) was improved by fusing them using a press with separately controlled plate temperatures of the press.

The plate temperatures are listed in Table ■. The upper plate has a smooth surface and has projections spaced in a pattern. In the case of Examples 1 to 4, two spacer sheets of tissue paper were placed between the nonwoven mat and the plate with projections to improve the strip tensile strength of the nonwoven mat made according to the conditions of Table I. was fused by using a spacer sheet of aluminum foil between the nonwoven mat and the smooth surface plate of the brace. In case of example 5,
Spacer sheets of aluminum foil were placed on both sides of the nonwoven mat to be fused. For Examples 6 to 9, a single spacer sheet of aluminum foil was used between the non-woven mat and the smooth surface plate of the brace, and a single spacer sheet of aluminum foil was used between the non-woven mat and the plate with the protrusions. I used U-paper spacer sheets. Example 2 For each of 1 through 9, the spacing between the land of the protrusion and the smooth surface plate is 0.005 inch (0.127 inch).
The plates were moved close together until the surface was fused (m77z), and fusion was performed for 1 minute. A 0.005 inch (0.127-) shim is provided in the gap between the plates. The nonwoven mats of Examples 10 to 15 (mats E to **I in Table I) are calendered to improve their high strip tensile strength.

The nonwoven mat is passed through heated calender rolls at a speed of 20 feet per minute (6.1 m) with a roller pressure of 700 p11 and a render roll temperature as described in Table 1.
In Examples 1 to 12, the laminated nonwoven sheets were manufactured by point welding.

The spot welding method used the same brace that was used when single nonwoven mats were fused together to improve strip tensile strength. The temperature of the plate (of the breath) is listed in Table ■. For Examples 1-4, the high strip tensile strength mat was placed on the bottom plate and the high tear resistance mat was in contact with the top plate. In all cases, tissue paper was used as a spacer sheet. For Examples 5-12, a high tear resistance mat was placed on the bottom plate and a high strip tensile strength mat was in contact with the top plate. Teishu paper was used again as a spacer sheet. In each of Examples 1-12, spot welding was performed for w seconds. The spacing between the smooth surface plate and the land on the protrusion of the other plate is 0.005 inches (0.1
27Wg! L), and in the case of Examples 7 to 9, 0.0
06 inches (0.152-), 0 for Examples 10 to 12
．． It was 0.008 inch (0.203 wn). The spacing was obtained by using shims. Examples 13 to 15
In this case, an adhesive was used to form the laminated nonwoven sheet.

Polyisobutylene rubber contact cement No. BW23R4-7
No. 5680A (manufactured by Polymer Industries, Inc., Springdale, Conn.) was applied to opposing sides of the high strip tensile strength mat and/or the high tear resistance mat and the opposing surfaces were bonded together in contact. The results of Examples 1 to 15 are shown in Table 3.

Table n shows that laminated nonwoven sheets with high strip tensile strength and high tear resistance are made from high strip tensile strength meltblown nonwoven mats and high tear resistance meltblown nonwoven mats.

Nonwoven sheets can be manufactured to have strip tensile strengths of 40001 T1 or greater and tear resistances of 400 d1 or greater. The highest tear resistance and strip tensile strength in the laminated nonwoven sheets was obtained when calendering was used to impart high strip tensile strength to the meltblown nonwoven mats and adhesives were used to laminate the mats. This is a preferred method of forming laminated nonwoven sheets, especially when high peel strength or delamination resistance is desired. The point welded laminated nonwoven sheet had a very low peel strength of about 0.5 bonds/inch (89.3 g/Cm) and was embossed with a plate stamp. Adhesive laminates, on the other hand, have smooth surfaces, very high peel strengths, and high tear layer deflections before layer delamination occurs. Examples 16-20 Of these examples, Examples 16-20 demonstrate the inverse relationship between strip tensile strength and tear resistance obtained with meltblown nonwoven mats.

Strip tensile strength and tear resistance were obtained by meltblowing polypropylene under essentially equal conditions (see Table 1) except for varying the die-to-collecting surface distance (D-C-D). The results are shown in the table.Short die collecting surface distance (
The melt-blown nonwoven mat made using Example 16) provided improved strip tensile strength, but very low tear resistance.

Conversely, when tear resistance was improved (Example 20), the strip tensile strength became very low. Example 21 This example demonstrates the increase in strip tensile strength of a nonwoven mat due to mat fusion.

Samples of nonwoven mat I produced under melt-blown conditions producing fibers with diameters of about 1 to 10 p (see Table 1) were heated using the calender rolls of Examples 10 to 14 at 90 C.
Heated calender roll temperature of 1601c, 700p
It was calendered once at a roller pressure of 11 and a line speed of 20 ft/min (6.1 m/min).

The results are summarized in Table W. As shown in Table W, 250.

Calender roll temperatures above 122'F (122'C) were effective in increasing the strip tensile strength of Nonwoven Mat I. In fact, the decrease in zero span tensile strength at the highest calender roll temperature as well as at intermediate temperatures, and the lack of an increase, indicate that sufficient pressure was applied to prevent shrinkage of the mat fibers. Also of note is that as the strip tensile strength was improved, the tear resistance of the nonwoven mat was reduced. Examples 22-28 demonstrate the effectiveness of point bonding techniques in increasing the strip tensile strength of other nonwoven mats made such as Nonwoven Mat I of Example 21.

Examples 22-28 Various nonwoven mats produced under melt-blown conditions producing fibers having diameters of about 1 to 10 microns (see Table I) were point bonded at elevated temperatures to fuse the fibers of the mats.

Fusing was carried out with the braces and plates of Examples 1-15. The plates were heated to the temperatures listed in Table V. The fusion was performed for m seconds with a spacing of 0.005 inch (0.005 mm) between the lands of the protrusions on the smooth surface of the upper plate and the lower plate.
．． 127wrIn). ” Crimp the mat until
I went. Except for Example 26, two sheets of tissue paper were used between the nonwoven mat and the lower plate and one sheet of foil was used between the nonwoven mat and the upper plate. Example 26 used two foils between it and the lower plate and two foils between it and the upper plate. As shown in Table V, the point bonded nonwoven mats exhibited high strip tensile strength. The strip tensile strength increased significantly compared to the untreated one. Examples 21 to 28 are approximately 300
It shows the tensile strength of a strip that can be produced when the tear resistance is less than or equal to drI1. As evidenced by Mats M, P, and Q in Table I, meltblown nonwoven mats can be produced with high tear resistance and low strip tensile strength. Processing high tear resistance mats produced under melt-blown conditions to produce relatively large diameter fibers, such as Mats P and Q, to produce nonwoven mats with increased strip tensile strength while maintaining high tear resistance. You can do it. To do this, the mat is fused by calendering or point bonding, as in Example 2, 30, preferably at a temperature below 138° C. and under sufficient pressure to prevent shrinkage of the fibers. Examples 29-30 Samples of 5mats P and Q were calendered at the temperatures and pressures shown in Table 1.

The calender roll pressure was 700 p1i) and the calender roll linear speed was 20 ft/min (6.1 m/min). Tear resistance of non-woven mats M, P and Q and Example 29
The tear resistance of treated nonwoven mats P and Q of 30 and 30 is approximately 2
It exhibits a relatively high range of tear resistance that can be produced with tensile strengths below 000 rT1.

As is presently apparent, the laminated nonwoven sheet of the present invention can be used for high tensile strength and high It has structural properties that make it suitable for applications that require both tear resistance and tear resistance.

Another special use for laminated nonwoven sheets is in battery separators. The mat is placed between the battery's anode and cathode plates,
Separate them. Of course, the permeability of this sheet is important in the battery, so it is preferable to fix the membranes using a point adhesion method, or to apply an adhesive, for example in spots or to glue fibers, but to close the gaps. Use a thin coating method to avoid forming an impermeable diaphragm. Further embodiments of the present invention include the following.

(1) said mat A having a relatively high strip tensile strength comprises bonded fibers with a diameter of about 1 to 10 μ; and said mat B having a relatively high tear resistance
2. A method according to claim 1, wherein the fibers are essentially entangled.

(2) The method according to claim 1, wherein the mat A contains self-bonded fibers.

(3) The method according to claim 1, wherein the mat A contains fused fibers. (4) The method according to claim 1, wherein the fibers in the mats A and B are polypropylene fibers. (5
) The mats A and B are laminated by point welding at a welding temperature sufficient to fuse the fibers of the mat A to the fibers of the mat B. the method of.

(6) adhesive 7 on at least one surface of the mat;
2. The method of claim 1, wherein the mats are laminated by coating the adhesive and bringing the surface of the mat coated with the adhesive into contact with the surface of another mat. (7) said strip having a high tensile strength and a tear resistance of at least 1000C by heating the strip A under pressure to a temperature of about 137C (270°F) to about 160C (320°F); 2. The method of claim 1, wherein each matte B is obtained by heating the matte B under pressure to a temperature of about 93°C (200'F) to about 125°C (245°F). .

(8) Said mat A having high strip tensile strength
from about 138°C (280°F) to about 149°C (30°C)
8. Process according to claim 7, characterized in that it is obtained by pressing on a flat plate at a temperature of 0'F).

(9) The nonwoven sheet according to claim 2, wherein the mat is a polypropylene fiber mat.

(10 The strip tensile strength of the mat is 5000r
9. The nonwoven sheet according to item 9 above, which has a T1 or more.

(11) The nonwoven sheet according to item 9 above, wherein the other mat has a tear resistance of 1000 d or more.

(12) The nonwoven sheet according to item 9, wherein the mat A is self-bonded.

(13) The nonwoven sheet according to item 9, wherein the mat A has fused fibers. (14) The nonwoven sheet according to item 9, wherein the mat B has fibers with a diameter of 10 μm or more. (15) Said mat B
15. The nonwoven sheet according to item 14, wherein the nonwoven sheet has fibers having a diameter of 15 to 25μ.

(16) The nonwoven sheet according to item 9, wherein the mat is laminated by point welding.

(17) The nonwoven sheet as described in item 9 above, wherein the mat is laminated with an adhesive.

(18) Although the nonwoven mats A and B contain fibers of the same thermoplastic polymer, they have major differences in tear resistance and tensile strength properties, with mat A having a strip tensile strength of 500 Dm1 or more and a strip tensile strength of 300 Dm1 or less. The mat A is manufactured with an air/polymer ratio of 140 or more and has a relatively high degree of self-bonding, while the nonwoven mat B has a tear resistance of at least 1000 d and 2000 r]1 Mat B has a tensile strength of: A nonwoven sheet according to claim 3 characterized by:

(19) The nonwoven sheet according to claim 3, characterized in that the fibers of mat A are fused.

(20) The nonwoven sheet according to claim 3, wherein mat A is directly laminated on mat B by point welding.

[Brief explanation of the drawing]

Figure 1 is an overall schematic diagram of the melt blowing process, Figure 2 is a detailed view of a longitudinal section of a die that can be used in the melt blow process, and Figure 3 is a diagram showing the fusion of the nonwoven mat or two dots. FIG. 3A is a schematic diagram of a brace used for welding, FIG. 3A is a schematic diagram of a calender roll that can be used in place of the brace, and FIG. 4 is a schematic diagram of a laminated nonwoven sheet of the present invention.

Claims (1)

[Scope of Claims] 1. A non-woven sheet battery separator comprising a laminated non-woven mat having at least two types of non-woven mats A and B made by a melt-blowing process made of the same thermoplastic polymer fibers, the mats comprising: A is made of fibers with a diameter of 1 to 10μ, has a strip tensile strength of more than 4000 m and a tear resistance of less than 300 dm^2, and has a relatively high degree of self-bonding, while the mat B
has a tear resistance greater than 400 dm^2 and a tensile strength less than 2000 m^2, is composed of fibers with a diameter of about 10 to 40 microns, and has a relatively low degree of self-bonding but a high degree of entanglement, and the laminated nonwoven 4 mats
A nonwoven sheet battery separator having a strip tensile strength of greater than 000 m and a tear resistance of at least 400 dm^2. 2. A method for producing a non-woven sheet battery separator having a strip tensile strength of greater than 4000 m^2 and a tear resistance of at least 400 dm^2, comprising: (a) at least two types of non-woven sheet battery separators made by the melt-blowing process made of the same thermoplastic polymer fibers; forming non-woven mats A and B whose primary difference lies in tear resistance and tensile strength properties; (b) laminating at least one mat A to at least one mat B; , said mat A has a strip tensile strength of greater than 4000 m, and 3
00 dm^2, produced with an air/polymer ratio greater than 140, has a relatively high degree of self-bonding, and has fibers with a diameter of 1 to 10 microns, said mat B having at least It has a tear resistance of 400dm^2 and a tensile strength of less than 2000m,
Produced with a smaller air/polymer ratio, about 10 to 4
The mat A has fibers with a diameter of 0μ, has a relatively low degree of self-bonding and a high degree of entanglement, and has a high strip tensile strength.
Said mat B obtained by heating to 60°C (270-320°F), while having a tear resistance of at least 400 dm^2, is heated to about 93-118°C (20°C) under pressure.
0-245°F).