JPH06272189A - Bulky synthetic pulp sheet and its use - Google Patents

Abstract

PURPOSE:To produce the bulky synthetic pulp sheet excellent in acid resistance, alkali resistance, chemical resistance, etc., and not deformed after the absorption of a liquid, and to provide a separator for a closed type lead battery as its suitable use. CONSTITUTION:This bulky synthetic pulp sheet is obtained by subjecting 50-90wt.% of three-dimensionally crimped synthetic pulp, 5-30wt.% of a binder capable of adhering the pulp, etc., at a lower temperature than the melting point or degradation temperature of the synthetic pulp, and <=40wt.% of a reinforcing material, to wet pulping to attain an apparent density of <=0.15g/cm<3> under a load of 200g/cm<2>, and a closed type lead battery separator comprising the bulky synthetic pulp sheet is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulky synthetic pulp sheet which does not lose its shape even after absorbing liquid and its use. More specifically, in addition to the above characteristics,
Further, the present invention relates to a bulky synthetic pulp sheet excellent in chemical resistance such as acid resistance and alkali resistance, and absorbability, and a sealed lead-acid battery separator which is a suitable use thereof.

[0002]

2. Description of the Related Art It has hitherto been proposed to make a bulky sheet for the purpose of absorbing liquid or imparting elasticity as a buffering action. These techniques are mainly composed of cellulose, and in order to impart bulkiness to them, for example, a means of adding a bent synthetic fiber or a three-dimensional crimped synthetic fiber (JP-A-3-269199) is adopted. There is.

[0003]

However, since these bulky sheets are mainly composed of cellulose, they are inferior in chemical resistance. For example, they are used for absorbing and retaining a liquid of a strong acid such as sulfuric acid. Was inappropriate. On the other hand, there is a strong demand for an article that absorbs leakage of chemicals, spills, and the like, and an article that retains an electrolytic solution therein, such as a separator used in a sealed lead-acid battery. ing.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to produce a bulky synthetic pulp sheet which can be manufactured at low cost, is easy to handle, does not deteriorate even if it absorbs strong acid, strong alkali, etc., and is not deformed. To provide.

[0005]

The present invention has been proposed to achieve the above object, and is characterized by obtaining a bulky sheet by using a synthetic pulp having specific physical properties. Is. That is, according to the present invention, 50 to 90% by weight of three-dimensionally crimped synthetic pulp
200 g /, which is obtained by wet-paper-making 5 to 30% by weight of a binder capable of adhering at a temperature lower than the melting point or decomposition temperature of the synthetic pulp and 40% by weight or less of a reinforcing agent.
A bulky synthetic pulp sheet having an apparent density of 0.15 g / cm ³ or less under a load of cm ² is provided.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the use of a three-dimensionally crimped synthetic pulp is an important feature. That is, as a result of the three-dimensional crimping of the synthetic pulp, voids are formed between the pulp fibers even after the wet papermaking, so that a bulky sheet can be obtained. The synthetic pulp has a freeness of 0.1 sec /
It is preferably g or more and 1.0 sec / g or less.
If the freeness is less than 0.1 sec / g, the entanglement between the fibers is insufficient, so that wet papermaking is practically impossible. Markedly adheres to the sheet, making it impossible to obtain a predetermined bulky sheet. The term "three-dimensionally crimped synthetic pulp" as used in the present invention means that it is identified by observation with an electron microscope, and at least some of the fibers are crimped, and the crimped It also means a synthetic pulp composed of fibers that are also three-dimensional.

< Synthetic pulp raw material > In the present invention,
The crimp type synthetic pulp used as a main material is a synthetic pulp obtained by treating a synthetic resin made of a thermoplastic resin, preferably a polyolefin resin, by a special method and crimping it three-dimensionally. That is, as a method for obtaining a crimped synthetic pulp, a thermoplastic resin-based synthetic pulp is equal to or higher than the temperature of the rising point of the melting curve obtained when the synthetic pulp is measured by DSC, the rising point + (melting point-rising point). There may be mentioned a method in which the resin is dispersed in a poor solvent for the resin at a temperature equal to or lower than the numerical value represented by × 3/4 and then flushed under atmospheric pressure or a reduced pressure lower than that.

As the synthetic pulp used in the present invention, a synthetic resin synthetic pulp is used, and a polyolefin synthetic pulp is particularly preferably used. Furthermore, a flash spinning method of a solution or emulsion is preferably used. Synthetic pulp itself is known, and examples of the thermoplastic resin include polyolefin, polyester, polyacrylonitrile, and polyamide. In particular, as the polyolefin synthetic pulp, those manufactured by various methods as described below can be used.

For details of the method for producing a polyolefin synthetic pulp, refer to Encyc-lopedia of Chemical Technology 3rd ed. Vo.
For example, a method in which melt-spun fibers are cut into short pieces and then beaten, a method in which solution flash or emulsion flash is performed and then beaten, etc. are exemplified. Among them, those produced by the emulsion flash method using polyvinyl alcohol (PVA) as a hydrophilic agent are preferably used. In this case, the PVA content is 0.0
It is preferably from 1 to 10% by weight.

Examples of the polyolefin used include homopolymers of olefins such as polyethylene and polypropylene, ethylene-propylene copolymers and ethylene-1.
-Butene copolymer, ethylene-4-methylpentene-1
Copolymers of ethylene and other α-olefins such as copolymers are preferable, and crystalline polyolefins are preferably used from the viewpoint of mechanical strength. The polyolefin-based synthetic pulp thus obtained has a fiber length of 0.1 to 10 mm, and the subsequent crimping treatment can be easily carried out.
It has the characteristics that it is excellent in paper-making properties and elasticity, and that a bulky sheet can be satisfactorily produced.

< Crimping Treatment > In the present invention, it is also an important feature that the above-mentioned synthetic pulp is heat-treated to be crimped. As the heat treatment method, (1) the poor solvent of the synthetic pulp is equal to or higher than the temperature of the rising point of the melting curve obtained when the synthetic pulp is measured by DSC, rising point + (melting point−rising point) × 3/4
At a temperature below the value represented by, the synthetic pulp is dispersed therein. The synthetic pulp concentration at this time is 100
It is g / liter or less, preferably 40 g / liter or less. The lower limit is arbitrary, but from the viewpoint of yield, it is about 10
It is preferably g / liter or more. (2) Next, the above-mentioned dispersion liquid is flushed through an orifice under a reduced pressure of atmospheric pressure or lower. At this time, the pressure difference across the orifice is 0.5 kgf / cm ² or more, preferably 3 kgf / cm ² or more. If this pressure difference is small, sufficient crimp cannot be applied to the synthetic pulp fiber. The diameter of the orifice is preferably 3 mm or more and 30 mm or less. If the diameter of the orifice is 3 mm or less, the synthetic pulp causes clogging of the orifice, which prevents flushing. Further, if the diameter of the orifice is 30 mm or more, sufficient shear force is not applied to the synthetic pulp and crimp does not occur.

< Binder > As the binder, a heat-bonding type binder which can be bonded at a temperature lower than the melting point or the decomposition temperature of the main synthetic pulp is used. As an example of this, the melting point is lower than the synthetic pulp of the main material, for example,
Polyolefins such as polyethylene and polypropylene,
Examples thereof include synthetic pulps obtained from polymers such as polystyrene, polymethyl methacrylate, polyacrylonitrile, vinylidene chloride resin, nylon, polyester, polyfluoroethylene, vinyl chloride resin and modacrylic resin.

Further, various synthetic fibers similar to the above synthetic pulp and the raw material, the core portion has a melting point higher than the melting point of the main material synthetic pulp, and the sheath portion has a melting point lower than the melting point of the synthetic pulp. , So-called sheath-core type composite fiber,
Polyolefin resin powder, low melting point polyester powder,
Examples thereof include at least one selected from the group consisting of vinyl chloride resin powder, epoxy resin powder, emulsion thereof, natural or synthetic rubber latex, and acrylic emulsion. Among these, it is preferable to use polyolefin-based synthetic pulp. This binder needs to have a melting point lower than that of the synthetic pulp as the main raw material, preferably 5 ° C. or more.

< Reinforcing Agent > Further, in the present invention, for the purpose of imparting strength to the sheet, for example, a polyolefin having a melting point or a decomposition temperature higher than the bonding temperature of the binder, such as polyethylene, polypropylene, polyolefin, polystyrene, polymethyl. Various synthetic fibers such as methacrylate, polyacrylonitrile, vinylidene chloride resin, nylon, polyester, polyfluoroethylene, vinyl chloride resin, modacrylic resin, glass fiber,
Inorganic fibers such as silica fibers, alumina silicate fibers and slag fibers, and acid resistant inorganic powders such as silica powder and diatomaceous earth can be blended as necessary.

< Sheet formation > In the present invention, a sheet is produced by wet papermaking after mixing the above-mentioned various raw materials. After the sheet is dried, heat treatment is performed. As a method of heat treatment, the above-mentioned sheet placed on a running mesh-like support is heated from above while vacuuming from above, and a hot air penetration type method in which the sheet is formed is mixed with a hot roll. Melt the low melting point binder,
Examples include a method of fixing the synthetic pulp of the main material, a method of melting and adhering the binder in a hot oven, an infrared heater, or a method of adhering the web by melting the binder using ultrasonic energy. From the viewpoint of heat treatment temperature and imparting bulkiness to the product, the hot air penetration type method is preferably used. A feature of the present invention is that bulkiness is exhibited by performing heat treatment after wet papermaking.

< Hydrophilic treatment > In the present invention, the sheet obtained as described above is subjected to a hydrophilic treatment to further improve the liquid absorbing property of the sheet. This hydrophilization treatment is carried out, for example, by immersing the above-mentioned mat in an aqueous solution of a surfactant or by spray-spraying on the above-mentioned mat and then drying. As the surfactant to be used, any of anionic, cationic, amphoteric and nonionic surfactants are preferably used. Further, the degree of hydrophilic treatment is such that the amount of the surfactant attached is 0.05 to 5.0% by weight, and more preferably 0.
It is preferably in the range of 2 to 2.0% by weight. Such hydrophilization treatment is particularly effective when synthetic pulp that has not been hydrophilized is used.

[0017]

EFFECTS OF THE INVENTION According to the present invention, since the three-dimensionally crimped synthetic pulp is used, a bulky synthetic pulp sheet can be easily obtained by a wet papermaking method, and the bulky sheet is Since synthetic pulp having excellent chemical resistance is used as the material, even if a chemical such as a strong acid or a strong alkali is absorbed, the chemical pulp can be well retained without being deteriorated or decomposed. Moreover, the bulky synthetic pulp sheet is inexpensive and easy to handle. There are various uses for this bulky synthetic pulp sheet that utilize its properties such as its excellent bulkiness, liquid absorption, and chemical resistance. Especially, it is used as a wiping material for spilled liquid chemicals, and also as a sealed type. It can be suitably used as a separator for a lead storage battery.

[0018]

EXAMPLES The present invention will be described below with reference to examples. In the examples, each physical property was measured by the following methods.

<Fiber length> FS made by Finnish Kayani
-200 type automatic fiber length measuring device.

<Freeness> Except that the basis weight of the sheet is changed to 500 g / m ² , the time required for discharging water is measured in seconds according to the standard of TAPPI-T221. Freeness is expressed in hours per gram of pulp.

<Apparent Density> A test piece of 100 mm × 100 mm is sampled one by one from the center of each of 10 sheets. For the thickness, use a 1st class dial gauge specified in JIS B 7503 or a measuring tool with an accuracy equal to or higher than 19.6kPa (20kgf / 100cm ² ) at any point on the retainer mat. Measured under pressure so that the ratio becomes, and take the average value. next,
Read the total mass of 10 test pieces up to 100 mg,
From this, the average mass per test piece is determined, and the apparent density is determined by the following formula. D = Apparent density of sheet (g / cm ³ ) W = Average mass per test piece (g) t = Average thickness per test piece (mm)

Example 1 The following raw materials were used. High-density polyethylene synthetic pulp Average fiber length 1.0 mm Average fiber diameter 10 μm DSC curve rising temperature 108 ° C. Melting point 135 ° C. PVA adhesion amount 2.0% (ratio to synthetic pulp) The above synthetic pulp was immersed in water at a concentration of 10 g / liter. After dispersion, the temperature was raised to 120 ° C. in an autoclave, and flushing was performed under atmospheric pressure through an orifice having a diameter of 10 mm. The obtained synthetic pulp was shrunk to 6/10 in the length direction with respect to the original synthetic pulp, and as a result of observation with an electron microscope, it was confirmed to be three-dimensionally crimped. The freeness of this product was 0.3 sec / g.

The synthetic pulp thus obtained is designated as A, and
The sheet was created according to the procedure. B. Linear low density polyethylene synthetic pulp (low melting point poly
Ethylene synthetic pulp) Average fiber length 1.0 mm Average fiber diameter 30 μm Melting point 125 ° C. The raw materials of A and B are A = 70% by weight, B = 30% by weight
At a ratio of 25 × 25c
Paper was made with a square paper machine of m. Dry the obtained sheet
Then, heat-treat for 5 minutes at 130 ° C with a circulating hot air dryer.
went. As a result, basis weight of 310 g / m² , Thickness 2.58
mm, bulk density 0.12 g / cm ³ Can get a sheet of
did it. Absorb sulfuric acid in this bulky sheet and leave for 7 days
However, the sheet does not discolor at all and deforms
I couldn't see it.

Example 2 The following raw materials were used. Polypropylene synthetic pulp Average fiber length 1.5 mm Average fiber diameter 30 μm DSC curve rising temperature 135 ° C. Melting point 165 ° C. PVA adhesion amount 1.5% (ratio to synthetic pulp) The above synthetic pulp was dispersed in water at a concentration of 20 g / l. Then, the temperature was raised to 150 ° C. in an autoclave, and flushing was performed under atmospheric pressure through an orifice having a diameter of 10 mm. The obtained synthetic pulp was shrunk to 7/10 in the length direction with respect to the original synthetic pulp, and as a result of observation with an electron microscope, it was confirmed to be three-dimensionally crimped. The freeness of this product was 0.3 sec / g.

The crimped synthetic pulp thus obtained is designated as C, and the proportion of each raw material is B = 30% by weight, C = 70% by weight.
A sheet was obtained in the same manner as in Example 1 except for the above. The obtained sheet has a basis weight of 313 g / m ² and a thickness of 2.61 m.
It was a bulky sheet having m and a bulk density of 0.12 g / cm ³ .
Similar to the sheet obtained in Example 1, this bulky sheet was stable to acid, and the sheet did not lose its shape.

Example 3 As a raw material, D. Heat-fusible composite fiber (Melty 40 manufactured by Unitika Ltd.)
80, fiber type = 4d, fiber length = 5 mm), and the ratio of each raw material is A = 70% by weight, B = 20% by weight, C = 1.
A sheet was obtained in the same manner as in Example 1 except that the amount was 0% by weight. The obtained sheet was a bulky sheet having a basis weight of 305 g / m ² , a thickness of 2.77 mm, and a bulk density of 0.11 g / cm ³ . Similar to the sheet obtained in Example 1, this bulky sheet was stable to acid, and the sheet did not lose its shape.

Comparative Example 1 As a raw material, E. High density polyethylene synthetic pulp Average fiber length 1.2 mm Average fiber diameter 20 μm Freeness 1.2 sec / g Melting point 135 ° C. The ratio of each raw material is B = 30% by weight, E = 70
A sheet was obtained in the same manner as in Example 1 except that the weight percentage was changed. The obtained sheet had a basis weight of 312 g / m ² and a thickness of 1.
It was a tight sheet having 42 mm and a bulk density of 0.22 g / cm ³ .

Comparative Example 2 As a raw material, F. High-density polyethylene synthetic pulp Average fiber length 1.5 mm Average fiber diameter 20 μm Freeness 6.3 sec / g Melting point 135 ° C. The ratio of each raw material is B = 30 wt%, F = 70
A sheet was obtained in the same manner as in Example 1 except that the weight percentage was changed. The obtained sheet had a basis weight of 310 g / m ² and a thickness of 1.
It was a tight sheet having a size of 15 mm and a bulk density of 0.27 g / cm ³ .

Example 4 As a raw material, G. Heat-fusible composite fiber (Melty 40 manufactured by Unitika Ltd.)
80, fiber type = 2d, fiber length = 5 mm) was used, and a sheet was obtained in the same manner as in Example 1 except that the ratio of each raw material was A = 80% by weight and G = 20% by weight. Then, a hydrophilic treatment was performed with an anionic surfactant (aqueous solution of sodium dialkylsulfosuccinate) to obtain a sheet containing 0.8% by weight of the surfactant. The separator properties of the obtained sheet were measured according to JIS C 2313 as shown below and are shown in Table 1. Also. Table 2 shows the results of assembling a battery using this sheet and measuring the battery performance.

< Water Retention Measurement Method > After the sample was immersed in water and sufficiently hydrated, the weight% of water contained in the separator relative to the weight of the separator when left in a vertical state in the air for 1 minute (in a suspended state). Was measured to make the water retention.

< Maximum Pore Diameter Measuring Method > A test piece 25 mmφ was immersed in a methanol solution, and pressure was gradually applied by an apparatus in which the inside of the pores was replaced with methanol, and bubbles (N ₂ The differential pressure at the time of appearance of (gas) is read, and the maximum pore diameter of the sample is obtained from the surface tension of methanol (σ≈23) based on the following formula. σ = surface tension of methanol dyn / cm g = gravity acceleration cm / sec ² H ₂ -H ₁ = head difference in manometer cm ρ ₁ = wave density in manometer g / cm ³ ρ ₂ = density of methanol g / cm ³ d = depth of methanol cm

Comparative Example 3 For comparison of battery performance, a battery using the most general glass separator as a sealed lead-acid battery separator was assembled and the battery performance was measured.
In addition, Table 1 shows the physical properties of the present glass separator.

[0033]

[0034]

For the 5-hour rate discharge capacity, the time from the start of discharge until the terminal voltage of the battery reached 1.70 V was measured and the time was taken as the discharge capacity. For the low temperature high rate discharge capacity, the time from the start of discharge until the terminal voltage of the battery reached 1.00 V was measured and the time was taken as the discharge capacity. As the voltage at the 5th second, the terminal voltage of the battery was measured at 5th second from the start of the discharge at the time of measuring the low temperature high rate discharge capacity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D04H 3/14 A 7199-3B D21H 15/04 15/10 H01M 2/16

Claims (10)

[Claims] 1. 50 to 90% by weight of a three-dimensionally crimped synthetic pulp and a binder 5 to 3 capable of adhering at a temperature lower than the melting point or the decomposition temperature of the synthetic pulp.
An apparent density of 0.15 g under a load of 200 g / cm ² obtained by wet papermaking with 0% by weight and 40% by weight or less of a reinforcing agent.
/ Cm ³ or less bulky synthetic pulp sheet. 2. The crimped synthetic pulp has a length of 8/1 as compared with a state in which the crimped synthetic pulp is not crimped in the fiber length direction.
The bulky synthetic pulp sheet according to claim 1, which is in the range of 0 to 2/10. 3. The bulky synthetic pulp sheet according to claim 1, wherein the crimped synthetic pulp has a freeness of 0.1 sec / g or more and 1.0 sec / g or less. 4. The bulky synthetic pulp sheet according to claim 1, wherein the material of the crimped synthetic pulp is a thermoplastic resin. 5. The crimped synthetic pulp has a melting point of a melting point obtained when the uncrimped synthetic pulp is measured by DSC of the synthetic pulp at a temperature equal to or higher than a temperature of a rising point, a rising point + (melting point). -Rising point) x 3/4
At a temperature not higher than the value represented by, the resin is dispersed in a medium composed of a poor solvent of the resin in a non-crimped state, and thereafter, it is made by flashing under atmospheric pressure or a reduced pressure of less than that. Any one of claims 1 to 4
The bulky synthetic pulp sheet according to the item. 6. The bulky synthetic pulp sheet according to any one of claims 1 to 5, wherein the non-crimped synthetic pulp according to claim 5 is a synthetic pulp produced by flash spinning. 7. The bulky synthetic pulp sheet according to claim 1, wherein the material of the synthetic pulp is polyolefin. 8. A synthetic pulp having a melting point of 5 ° C. or more lower than the melting point or decomposition temperature of the crimped synthetic pulp of the main material as the binder, or the melting point of the synthetic pulp of which the core portion is the main material. The bulky synthetic pulp sheet according to claim 1, which uses a sheath-core type composite fiber having a high melting point and a sheath portion having a melting point lower than the melting point of the main synthetic pulp by 5 ° C or more. 9. The reinforcing agent is at least one selected from the group consisting of various synthetic fibers, composite heat-bonding fibers, acid-resistant inorganic fibers, and acid-resistant inorganic powders. The bulky synthetic pulp sheet according to item 1. 10. A sealed lead-acid battery separator comprising the bulky synthetic pulp sheet according to any one of claims 1 to 9.