JPH07290627A - Nonwoven fabric laminate superior in liquid retention - Google Patents

Abstract

PURPOSE:To obtain a substrate having liquid retention characteristics so high that it can retain liquid, such as electrolyte, at a high rate and keep its high retentivity even if being pressurized after retaining liquid once by a method wherein a laminate is made of a three-layer nonwoven fabric in which an intermediate layer is made of a nonwoven fabric of a rough structure and each outer layer is made of a nonwoven fabric of a dense structure. CONSTITUTION:A nonwoven fabric laminate is made of a three-layer nonwoven fabric in which each outer layer is made of a dense nonwoven fabric and an intermediate layer is made of a rough nonwoven fabric. The dense nonwoven fabric forming each outer layer preferably has an average fiber diameter of 0.05-15mum and is desirably produced by spraying melt fiber in a melt blow method in consideration of liquid retention characteristics and the like required as a battery separator and the like. If the dense nonwoven fabric forming each outer layer has an average fiber diameter less than 0.05mum, electrolyte or other liquid is hard to infiltrate into the laminate, and the laminate is hard to produce. On the other hand, if more than 15mum, liquid retained once is released by being pressurized. Therefore, a dense nonwoven fabric out of this range is insufficient in liquid retention characteristics as the requirement of a battery separator and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonwoven fabric laminate having an excellent liquid retaining property, and more particularly, a three-layer structure polyolefin nonwoven fabric laminate having an excellent electrolyte retaining property and useful as a separator for alkaline batteries. Regarding

[0002]

2. Description of the Related Art Nylon, polypropylene non-woven fabric, etc. are mainly used as separators for alkaline batteries, but the latter has recently been used because of its degradability in alkaline electrolyte. Many. However, since polypropylene is hydrophobic, it is difficult for the electrolytic solution to soak into the base material, and even if the electrolytic solution is once held, the electrolytic solution escapes by applying pressure. Therefore, the liquid retention property required as a battery separator was insufficient. As a method for improving it, there is a method in which a polypropylene nonwoven fabric is impregnated with a surfactant or a hydrophilic monomer such as acrylic acid is grafted. Incidentally, the liquid retention characteristics here, after holding the electrolytic solution and the electrolytic solution sufficiently,
Furthermore, it is a general term for the electrolytic solution retention rate after the pressurization treatment.

However, a single-layer polypropylene nonwoven fabric cannot satisfy the liquid retention characteristics required for a battery separator. Further, when the acrylic acid monomer is subjected to electron beam graft polymerization to impart permanent hydrophilicity, it is necessary to increase the graft ratio in order to satisfy the liquid retention property, which lowers the production efficiency and deteriorates the substrate due to radiation. Connected to. That is, in order to obtain a high grafting rate, the electron beam irradiation conditions or the graft reaction conditions may be strict, but the deterioration of the substrate or the decrease in production efficiency (extension of reaction time, increase of reaction temperature) may occur. However, it is not preferable because it leads to an increase in the amount of the monomer).

[0004]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a substrate with good liquid retention properties, a high liquid retention rate of an electrolytic solution, and the like.
It is to obtain a base material having a high liquid retention rate even if pressure treatment is performed. Further, an object of the present invention is to obtain a sufficient liquid retention property with a lower grafting rate than in the past, thereby,
It is an object of the present invention to provide a technique capable of suppressing deterioration of a substrate due to electron beam irradiation to a minimum and improving production efficiency by shortening a grafting reaction time. The present invention, particularly when used as a battery separator,
It is to obtain a polyolefin base material having good liquid retention properties and a high electrolytic solution retention rate, and having a high electrolytic solution retention rate even after being once held and then subjected to pressure treatment.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a non-woven fabric having a three-layer structure in which an intermediate layer is a non-woven fabric having a coarse structure and both outer layers are a non-woven fabric having a dense structure. TECHNICAL FIELD The present invention relates to a laminate, and a nonwoven fabric laminate obtained by graft-polymerizing a radically polymerizable compound to the nonwoven fabric laminate having the three-layer structure by irradiation of radiation or plasma, particularly a nonwoven fabric laminate useful as a separator for alkaline batteries. In a preferred embodiment, each non-woven fabric having the three-layer structure is composed of polyolefin fibers, and the filling rate of each non-woven fabric in the non-woven fabric laminate having the three-layer structure is 1 to 60%. The average fiber diameter of the component is 0.05
〜15 μm, the basis weight is 5 to 270 g / m ² , the ratio in the three-layer structure based on the basis weight is 10 to 90%,
The average fiber diameter of the non-woven fabric having a coarse structure is 15 to 100.
μm, the basis weight is 5 to 270 g / m ² , and the ratio in the three-layer structure based on the basis weight is 90 to 10%, and the non-woven fabric laminate obtained by the graft polymerization (hereinafter,
(Although it may be referred to as a grafted non-woven fabric laminate), a non-woven fabric laminate having a three-layer structure is contacted with a solution containing a polar radically polymerizable compound having a polar alcohol of 15 vol% or more, and then irradiated with radiation. The present invention relates to a grafted nonwoven fabric laminate obtained by graft-polymerizing the radically polymerizable compound.

The nonwoven fabric laminate of the present invention is composed of a three-layer structure nonwoven fabric laminate. The non-woven fabric laminate is required to be composed of a non-woven fabric in which both outer layers are dense and a middle layer in which it is coarse. The non-woven fabric may be of a dry method or a wet method, and may be formed by a melt blow method, a spun bond method, a spun lace method, a card regardless of whether an adhesive is used or not. It is also possible to use a method such as a method, a papermaking method, or a dry thermal bond method. The dense non-woven fabric constituting both outer layers preferably has an average fiber diameter of 0.05 to 15 μm, and in view of the liquid retention characteristics required for a battery separator or the like, a melt blowing method by spraying molten fibers Those formed in are preferred. When the average fiber diameter of the dense nonwoven fabrics constituting both outer layers is less than 0.05 μm, the laminate is less likely to be impregnated with a liquid such as an electrolytic solution, and is also difficult to manufacture. On the other hand, when the thickness exceeds 15 μm, the liquid escapes by pressurizing even if the liquid is once held. Therefore, if it exceeds the range, the liquid retaining property required as a battery separator or the like becomes insufficient. The coarse non-woven fabric constituting the intermediate layer preferably has an average fiber diameter of 15 to 100 μm. In this case, non-woven fabrics formed by various methods can be used without particular preference to the production method. When the average fiber diameter of the coarse non-woven fabric constituting the intermediate layer is less than 15 μm, the laminate is less likely to be impregnated with a liquid such as an electrolytic solution. On the other hand, when it exceeds 100 μm, the liquid is retained by applying pressure even if the liquid is once retained. If it escapes, and if it deviates from the range, the liquid retaining property required for a battery separator or the like becomes insufficient. The basis weight of the dense non-woven fabric forming the outer layers and the coarse non-woven fabric forming the intermediate layer is
It is preferably 5 to 270 g / m ² , respectively. If the basis weight deviates from the range, it becomes difficult for a liquid such as an electrolytic solution to soak into the laminate, or even if the liquid is once held, the liquid escapes due to pressurization, which is required for a battery separator or the like. Insufficient liquid properties. The cross-sectional structure of the nonwoven fabric laminate of the present invention is a dense structure nonwoven fabric / a coarse structure nonwoven fabric / a dense structure nonwoven fabric in the thickness direction. The filling rate of each non-woven fabric in the non-woven fabric laminate having the three-layer structure is preferably 1 to 60%. Here, the filling rate is simply the degree of fluffiness of the non-woven fabric, which is derived from the following equation. Unit weight / (density of polymer forming fibers of non-woven fabric x thickness of non-woven fabric) is 100
It is the doubled value (%). If the filling rate of each nonwoven fabric is less than 1%, the porosity is too large to hold the liquid. On the other hand, even if it exceeds 60%, the degree of fluffiness is insufficient, and it becomes difficult for the liquid such as the electrolytic solution to soak into the laminate, and even if the liquid is once held, the liquid escapes due to pressurization. Considering the matter, the filling rate is 5 to 30%.
Is more preferable. In the nonwoven fabric laminate of the present invention, the proportion of the dense nonwoven fabric constituting both outer layers to the whole is too large or too small, and good liquid retention properties cannot be obtained. The same applies to the coarse nonwoven fabric that constitutes the intermediate layer. The ratio in the three-layer structure based on the basis weight of the dense nonwoven fabric constituting both outer layers is 10 to 90.
%, And the same proportion of the coarse nonwoven fabric constituting the intermediate layer is preferably 90 to 10%. When the proportion of the dense nonwoven fabrics constituting both outer layers is less than 10% and the proportion of the coarse nonwoven fabrics constituting the intermediate layer exceeds 90%, the liquid escapes by pressurizing even if the liquid is once held, The liquid retention properties required for separators for vehicles are insufficient. On the other hand, the proportion of dense non-woven fabric constituting both outer layers exceeds 90%, and the proportion of coarse non-woven fabric constituting the intermediate layer is 10%.
If it is less than%, it becomes difficult for a liquid such as an electrolytic solution to soak into the laminate, and the liquid retaining properties required for a battery separator or the like will be insufficient. Unit weight of the whole nonwoven fabric laminate (g /
m ² ) is preferably 10 to 300 g / m ² ,
More preferably, it is 30 to 80 g / m ² . Further, the total thickness thereof varies depending on the application, but for example, the thickness after calendering as a battery separator is 2
A thickness of 00 μm or less is preferable from the viewpoint of reducing the overall weight and improving the energy density by increasing the active substances of the electrodes. The nonwoven fabric laminate of the present invention, for example, a rough nonwoven fabric as an intermediate layer,
It can be formed by laminating dense non-woven fabrics on the inner and outer layers and crimping the ends thereof with an impulse sealer or the like.

Each of the non-woven fabrics used to form the non-woven fabric laminate of the present invention is, for example, polypropylene (hereinafter referred to as P
P), polyethylene (hereinafter sometimes referred to as PE) and other polyolefins, polyester, and polyphenylene sulfide (PPS) fibers. In particular, considering the use of the alkaline battery separator, polyolefin fibers such as PP and PE, especially polypropylene fibers, are preferable. Further, polyolefin fibers are non-polar, when the surface or the like is to be modified by a graft method by irradiation with radiation,
This is because the grafting monomer is repelled on the surface, which often does not lead to an improvement in the grafting rate.
Examples of polypropylene that constitutes the polypropylene fiber include homopolypropylene or a copolymer of propylene and ethylene or α-olefin such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The copolymer may be a random copolymer or a block copolymer.
The polypropylene resin is, for example, a transition metal compound catalyst component such as titanium trichloride or titanium tetrachloride, or a catalyst component obtained by supporting them on a carrier containing magnesium halide such as magnesium chloride as a main component, triethylaluminum, and diethylaluminum chloride. It is prepared using a catalyst system in combination with an organoaluminum compound such as The melt flow rate (JIS K7210, load 2.16 kg, 230 ° C., hereinafter referred to as MFR) of the polypropylene resin is usually 0.1 to 100 g / 10 minutes.

In addition to the above resins, crystal nucleating agents, antioxidants such as phenol-based antioxidants and sulfur-based antioxidants, ultraviolet absorbers, light stabilizers, inorganic fillers, antistatic agents, antifogging agents, antibrows. Other additives such as a bulking agent, a lubricant, a pigment and a dye may be appropriately added if necessary.

The grafted nonwoven fabric laminate of the present invention can be obtained by graft-polymerizing a radically polymerizable compound to the above-obtained three-layered nonwoven fabric laminate by irradiation of radiation or plasma. Here, radiation means α rays, γ rays, β rays (electron rays), neutron rays, X rays, and the like. Among these radiations, the electron beam is preferable from the viewpoint of handling and grafting efficiency. The electron beam irradiation condition is an acceleration voltage of 150 to 5000 kV, preferably 2
Appropriate values are from 00 to 1000 kV and an irradiation dose of 5 to 500 kGy, preferably about 50 to 200 kGy. If the irradiation dose is less than 5 kGy, the grafting will not be carried out sufficiently, while if it exceeds 500 kGy, the grafting ratio will not be improved and the substrate will be severely deteriorated. This irradiation is usually performed under an air atmosphere, preferably under an atmosphere of an inert gas such as nitrogen or argon. Further, plasma irradiation is performed by a low temperature plasma treatment method. The low-temperature plasma method is a high-frequency discharge, a microwave discharge, etc., and a low-pressure oxidizing gas such as oxygen or a gas in which nitrogen, air, argon, helium, or the like is mixed is excited to generate an active gas. It can be performed by contacting the substrate. The processing condition is that the pressure is 0.1 to 10 torr and the processing time is 15
Seconds or more, preferably 20 to 40 seconds. The grafting rate of the radically polymerizable compound is up to 50 wt%. Fifty
If it exceeds wt%, there is no liquid retaining effect and it is uneconomical. The lower limit is not particularly limited because it shows an effect as compared with that of a single layer even when not grafted, but the increase in the liquid retention rate is particularly noticeable at 2 wt%, and therefore preferably at 2 to 35 wt%. is there.

Examples of the radically polymerizable compound include:
An unsaturated carboxylic acid or its derivative is mentioned. Examples of the unsaturated carboxylic acid or its derivative include acrylic acid, methacrylic acid, maleic acid, endobicyclo [2.2.1] -5-heptene-2,3-dicarboxylic acid (endic acid), fumaric acid, tetrahydrophthalic acid. Unsaturated mono- or dicarboxylic acids such as itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid, or derivatives thereof, such as acid halides, amides, imides, anhydrides, and esters. Specific examples of the derivative include maleinyl chloride, maleimide, maleic anhydride, endic anhydride, methyl acrylate, methyl methacrylate, citraconic anhydride, monomethyl maleate, dimethyl maleate and the like. In the present invention, radical polymerization reactive oligomers, for example, urethane-based oligomers and ether-based oligomers having a polymerizable functional group,
An ethite-based oligomer or the like can also be used.

The method for grafting the laminate may be either a pre-irradiation method or a simultaneous irradiation method. In a particularly preferred embodiment, the non-woven fabric laminate having the three-layer structure is contacted with a solution containing a radically polymerizable compound having a polarity, in which a lower alcohol is added in an amount of 15 vol% or more, and then irradiated with radiation to produce the radically polymerizable compound. The compound is graft polymerized. By using a lower alcohol like this,
Easy application and impregnation of a polar radical-polymerizable compound (hereinafter sometimes referred to as a graft monomer) -containing solution (particularly an aqueous solution) containing a polar non-woven fabric laminate such as a polyolefin substrate onto the surface of the laminate. In addition to the above, the solution or the like can be made to exist even in the pores, and it becomes easy to improve the liquid retaining property. Specific examples of the lower alcohol include methanol, ethanol, 2-propanol, 1-propanol and the like. Methanol, ethanol and 2-propanol are preferable because of the efficiency of the graft treatment.

In the grafting treatment, the grafting monomer is usually diluted with water or another solvent and the lower alcohol and contacted with the three-layered nonwoven fabric laminate by a method such as coating, impregnation or spraying. A preferable blending ratio of the lower alcohol in the whole diluting solvent is 15 vol% or more, and preferably 20 vol% or more. If it is less than 15 vol%, not only is it difficult to apply and impregnate the surface of the laminate with a polar graft monomer solution (particularly an aqueous solution) for a non-polar nonwoven fabric laminate such as a polyolefin substrate, and even up to the inside of the pores. However, it becomes difficult to allow the solution or the like to exist, and it becomes difficult to improve the liquid retention property. The diluting solvent may consist only of lower alcohol. The blending ratio varies depending on the individual lower alcohol, for example, for methanol, 50 vol%
Or more, preferably 60 vol% or more, and for ethanol, 25 vol% or more, preferably 40 vol% or more, 2
Outside the propanol, the content is preferably 15 vol% or more, preferably 20 vol% or more. When the content deviates from this range, the interfacial tension of the graft monomer solution is lowered to facilitate coating / impregnation, and even within the pores. It becomes difficult to allow a solution or the like to exist, and it becomes difficult to improve the liquid retaining property. The blending ratio of the grafting monomer is selected depending on the use of the nonwoven fabric laminate, but in order to graft uniformly in a short time, it is 5 to 100 parts by volume of the lower alcohol-containing diluent solvent.
100 parts by volume is preferable, and 10 to 50 parts by volume is more preferable for uniform grafting in a shorter time.

[0013]

EXAMPLES The present invention will now be described in detail with reference to Examples and Comparative Examples.

The non-woven fabric used in the following examples and comparative examples has the following constitution. M15: PP melt blown non-woven fabric, basis weight 15 g / m
² , fiber diameter 5 μm, filling rate 16% M45: PP melt blown nonwoven fabric, basis weight 45 g / m
² , fiber diameter 5μm, filling rate 13% S15: PP dry thermal bond nonwoven fabric, fabric weight 15
g / m ² , fiber diameter 19 μm, filling rate 24% S20: PP dry thermal bond nonwoven fabric, fabric weight 20
g / m ² , fiber diameter 19 μm, filling rate 24% S45: PP dry thermal bond nonwoven fabric, basis weight 45
g / m ² , fiber diameter 20 μm, filling rate 20%

The samples in the examples and comparative examples were prepared according to the following method. Moreover, the measuring method of a physical-property value is as follows. Preparation of sample: Pre-dried in a dryer at a temperature of 40 ° C,
Keep the moisture content below the official moisture content (JIS-L1096;
Based on the general textile test method). After that temperature 23 ℃, humidity 6
It is left in a 0% test room to adjust the water balance (JIS-
Z8703; conforms to standard conditions of test site). (1) Grafting rate (wt%): Calculated based on the following formula from the amount of weight change before and after the graft reaction. Grafting rate (wt%) = (W ₂ −W ₁ ) / W ₁ X10
0 W ₁ : Weight before reaction (g) W ₂ : Weight after reaction (g) (2) Liquid retention rate: Thickness 0.18-by calendering
A sample having a size of 0.20 mm was sampled in a size of 100 × 100 mm, and this test piece was immersed in an aqueous KOH solution having a specific gravity of 1.3 for 1 hour and then pulled out of the solution and the weight of the test piece after 10 minutes was measured before immersion. The rate of increase in weight was calculated in comparison with the weight and used as the liquid retention rate. (3) Liquid retention rate after pressurization: Thickness 0.1 by calendering
A sample having a size of 8 to 0.20 mm was sampled in a size of 100 × 100 mm, the test piece was immersed in an aqueous KOH solution having a specific gravity of 1.3 for 1 hour, then taken out, pinched with filter paper, and pressed with a hand press for 1 minute. (50 kg / cm ² ). After that, the weight of the test piece was measured, and the rate of increase in weight before the measurement was defined as the pressurized liquid retention rate.

Example 1 M15 (PP meltblown nonwoven fabric, basis weight 15 g / m
² , fiber diameter 5 μm, filling rate 16%) / S15 (PP dry thermal bond nonwoven fabric, basis weight 15 g / m ² , fiber diameter 19 μm, filling rate 24%) / M15 (PP meltblown nonwoven fabric, basis weight 15 g / m ² , Nonwoven fabrics were laminated in this order with a fiber diameter of 5 μm and a filling rate of 16%), and the end faces were pressure-bonded by an impulse sealer to obtain a single laminated body. The liquid retention rate and the liquid retention rate after pressurization of the laminate having the three-layer structure were measured. The results are shown in Table 1.

Example 2 The impregnating solution was impregnated with the laminate having the three-layer structure obtained in Example 1 for 3 minutes, and the clearance was 300 μm and the pressure was 6 k.
After the amount of impregnating solution was made uniform by passing through a squeezing roll of g / cm ² , acrylic acid was graft-polymerized under the following conditions by the electron beam simultaneous irradiation method. Electron beam irradiation conditions; acceleration voltage 500 kV, irradiation dose 50 k
Gy, irradiation in air Grafting conditions; Composition ratio of impregnating solution (vol%) Acrylic acid: DVB: IPA: H ₂ O = 20: 0.6:
20:60 However, DVB ... divinylbenzene, IPA ... isopropyl alcohol Solution temperature 35 ° C. After the graft reaction, washing and drying treatments are performed to obtain a grafted nonwoven fabric laminate with a graft ratio of 10 wt%, The liquid rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

Example 3 In Example 1, instead of the nonwoven fabric of S15, S20 (P
Dry thermal bond non-woven fabric made of P, basis weight 20 g / m ² ,
Fiber diameter 19 μm, filling rate 24%)
A non-woven fabric laminate having a three-layer structure was obtained in the same manner as in Example 1,
The liquid retention rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

Example 4 Using the three-layered nonwoven fabric laminate obtained in Example 3,
Example 2 except that the graft ratio was 7 wt%
The graft reaction was performed in the same manner as in 1. to obtain a grafted nonwoven fabric laminate, and the liquid retention rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

Example 5 A grafted nonwoven fabric laminate having a three-layer structure was obtained in the same manner as in Example 2 except that the grafting ratio was set to 31% by weight, and its liquid retention rate and After pressurization, the liquid retention rate was measured. The results are shown in Table 1.

Example 6 Instead of the nonwoven fabric of S15 in Example 1, S45 (P
Dry thermal bond non-woven fabric made of P, basis weight 45 g / m ² ,
Fiber diameter 20 μm, filling rate 20%)
A non-woven fabric laminate having a three-layer structure was obtained in the same manner as in Example 1,
The liquid retention rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

Example 7 Using the three-layered nonwoven fabric laminate obtained in Example 6,
Example 2 except that the graft ratio was 8 wt%
The graft reaction was performed in the same manner as in 1. to obtain a grafted nonwoven fabric laminate, and the liquid retention rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

Example 8 A grafted nonwoven fabric laminate having a three-layer structure was obtained in the same manner as in Example 2 except that the graft ratio was changed to 3 wt%. The after-retention rate was measured. The results are shown in Table 1.

Comparative Example 1 M45 (PP meltblown non-woven fabric, basis weight 45 g / m
² , fiber diameter 5 μm, filling rate 13%) The base fabric was constructed using only non-woven fabric. The liquid retention rate and the liquid retention rate after pressurization of this single-layer structure base fabric were measured. The results are shown in Table 1.

Comparative Example 2 Using the single-layer structure base fabric obtained in Comparative Example 1, Example 2 was used.
Grafting reaction was carried out in the same manner as above, followed by washing with water and drying in the same manner, the graft ratio was determined according to the above-mentioned measuring method, and the liquid retention rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

Comparative Example 3 In Comparative Example 1, instead of the M45 non-woven fabric, S45 (P
Dry thermal bond non-woven fabric made of P, basis weight 45 g / m ² ,
Fiber diameter 20 μm, filling rate 20%)
A base fabric was constructed in the same manner. The liquid retention rate and the liquid retention rate after pressurization of this single-layer structure base fabric were measured. The results are shown in Table 1.

COMPARATIVE EXAMPLE 4 Using the single-layer structure base fabric obtained in Comparative Example 3, Example 2 was used.
Grafting reaction was carried out in the same manner as above, followed by washing with water and drying in the same manner, the graft ratio was determined according to the above-mentioned measuring method, and the liquid retention rate and the liquid retention rate after pressurization were measured. The results are shown in Table 1.

[0028]

[Table 1]

From the results shown in Table 1, according to the examples of the present invention, the electrolyte retention rate was improved and the electrolyte retention rate after pressurization was also improved. It can be seen that a nonwoven fabric laminate having excellent liquid retaining properties is obtained, and the grafting further improves the liquid retaining ratio of the electrolytic solution and also improves the liquid retaining ratio of the electrolytic solution after pressurization.

[0030]

As described above, according to the present invention, a non-woven fabric laminate having excellent liquid retention properties can be obtained, and at the time of grafting, it is possible to obtain one having sufficient liquid retention properties with a lower grafting ratio than before. Therefore, in the grafting, it is not necessary to make more severe conditions such as deterioration of the base material under radiation irradiation conditions, and the production efficiency can be improved by shortening the grafting reaction time. Since the non-woven fabric laminate of the present invention is excellent in the liquid retaining property of the electrolytic solution, it is particularly suitable for a separator of an alkaline battery, and in particular, a nickel-based (Ni-Cd, Ni-MH) alloy which is strictly required to have the liquid retaining property. It is useful as a secondary battery separator, but because of its improved liquid retention properties,
In addition, it can be used for filters, various separation membranes, various water absorbing materials, oil absorbing materials, etc.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01M 2/16 LG

Claims (6)

[Claims] 1. A non-woven fabric laminate excellent in liquid retention, characterized in that the intermediate layer is a non-woven fabric having a coarse structure and both outer layers are made of a non-woven fabric having a dense structure. 2. The non-woven fabric laminate having excellent liquid retention according to claim 1, wherein each non-woven fabric having a three-layer structure is composed of polyolefin fibers. 3. The filling rate of each non-woven fabric in a three-layer non-woven fabric laminate is 1 to 60%, the average fiber diameter of the non-woven fabric having a dense structure is 0.05 to 15 μm, and the basis weight is 5 to 27.
0 g / m ² , the proportion in the three-layer structure based on the basis weight is 10 to 90%, the average fiber diameter constituting the rough nonwoven fabric is 15 to 100 μm, and the basis weight is 5 to 270 g /
m ² and the ratio in the three-layer structure based on the basis weight is 9
The nonwoven fabric laminate excellent in liquid retention according to claim 1, which is 0 to 10%. 4. The liquid retaining composition according to claim 1, which is formed by graft-polymerizing a radical-polymerizable compound on a non-woven fabric laminate having a three-layer structure by irradiation with radiation or plasma. Nonwoven fabric laminate with excellent properties. 5. A non-woven fabric laminate having a three-layer structure is brought into contact with a solution containing a polar radically polymerizable compound having a polar alcohol content of 15 vol% or more, and then irradiated with radiation or plasma to obtain the radical polymerization property. The nonwoven fabric laminate excellent in liquid retention according to any one of claims 1 to 4, wherein a compound is graft-polymerized to the nonwoven fabric laminate. 6. The non-woven fabric laminate excellent in liquid retention according to any one of claims 1 to 5, wherein the non-woven fabric laminate is for a separator of an alkaline battery which is excellent in liquid retention of an electrolytic solution.