JPH11315462A - Melt-blown nonwoven fabric made of polyarylene sulfide and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melt-blown nonwoven fabric made of a polyarylene sulfide having high strength, heat-resistance and chemical resistance and ultrafine fiber diameter. SOLUTION: A melt-blown nonwoven fabric 9 made of ultrafine polyarylene sulfide fiber is produced by mixing an organic acid or inorganic acid to a reaction liquid after completing the polymerization reaction of polyarylene sulfide, washing the mixture and blowing the mixture in molten state. The polyarylene sulfide fiber has a weight-average molecular weight of 10,000-20,000 and a crystallization temperature of 220-260 deg.C. The melt-blowing is carried out by extruding a molten mixture of polyarylene sulfide through a nozzle 10 adjusted to 280-400 deg.C and, at the same time, drawing with hot air stream of 290-420 deg.C and collecting the produced ultrafine fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyarylene sulfide melt-blown nonwoven fabric and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the development of electronics technology, batteries and capacitors have come to be used not only in various electric devices such as memory backup power supplies, but also in the interior of the engine room of automobiles. It has been used in a wide range of fields such as various industrial equipment. In addition, the use environment of these devices is often high temperature and high humidity. Therefore, the heat resistance of battery constituent materials (battery case, gasket, separator, etc.) has been improved to withstand such a severe use environment.

[0003] In particular, separators greatly contribute to miniaturization of batteries, so that they are required to be excellent not only in strength but also in heat resistance and chemical resistance. Conventionally, polypropylene has been widely used as a resin satisfying such requirements. However, batteries used as a memory backup power supply are reflow-soldered on a printed circuit board together with the memory element after soldering the soldering terminals.At that time, the heat melts the polypropylene and short-circuits occur. is there.

In order to improve the heat resistance and the like of the separator, it has been proposed to use a nonwoven fabric of polyarylene sulfide (PAS) having a high melting point and excellent alkali resistance. For example, Japanese Unexamined Patent Publication No. 63-315655 discloses a nonwoven fabric comprising fibers having an average fineness of 0.5 denier or less, and at least a part of the fibers is fused or entangled, and has a basis weight variation of 7% or less. It discloses that a polyphenylene sulfide polymer having a weight average molecular weight of 20,000 to 70,000 is used in melt-blowing a polyphenylene sulfide polymer into a spun fiber by using a polyphenylene sulfide melt-blown nonwoven fabric.

As described above, a conventional nonwoven fabric of polyarylene sulfide uses a polyarylene sulfide having a weight average molecular weight of 20,000 or more in order to obtain sufficient strength. There was a problem that the average fiber diameter of the fibers became large.

Accordingly, an object of the present invention is to provide good strength,
An object of the present invention is to provide a melt-blown nonwoven fabric made of polyarylene sulfide having heat resistance and chemical resistance and having a very small fiber diameter, and a method for producing the same.

[0007]

Means for Solving the Problems In view of the above object, as a result of intensive studies, the present inventors have found that a non-woven fabric made of polyarylene sulfide fibers having a specific molecular weight and a crystallization temperature has an extremely small average fiber diameter. In addition, the inventors have found that they maintain good strength, and have reached the present invention.

[0008] That is, the melt-blown nonwoven fabric of the present invention is characterized by comprising a polyarylene sulfide fiber having a weight average molecular weight of 10,000 to 20,000 and a crystallization temperature of 220 to 260 ° C.

The method for producing a melt-blown nonwoven fabric according to the present invention comprises the steps of: (a) melting and kneading polyarylene sulfide;
(b) Discharged from a nozzle set at 280-400 ° C and drawn by high-temperature air at 290-420 ° C to form fine fibers, and (c) the obtained fibers are collected in a collecting section. .

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below.

[1] Meltblown nonwoven fabric The meltblown nonwoven fabric of the present invention has a weight average molecular weight of 10,000.
It is composed of polyarylene sulfide fibers having a crystallization temperature of from 220 to 260 ° C.

(A) Polyarylene Sulfide (PAS) The polyarylene sulfide comprises at least 70 mol%, preferably at least 90%, of the repeating units of the skeleton represented by the following general formula:

Embedded image Or a homopolymer or copolymer comprising an arylene sulfide unit represented by

The above repeating unit has the following general formula in the range of 30 mol% or less:

Embedded image (Wherein R ₁ is an alkyl group, a nitro group, a phenyl group or an alkoxy group).

[0014] PAS can be produced by reacting an alkali metal sulfide with a dihalide.

As the alkali metal sulfide, lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide,
Cesium sulfide and the like. Further, an alkali metal hydrosulfide and an alkali metal hydrate corresponding to the alkali metal sulfide may be neutralized with an alkali metal hydroxide. Among them, sodium sulfide is preferable because it is inexpensive.

The dihalide is represented by the following general formula:

Embedded image (Where X represents a halogen atom, and R represents a carbon atom 1 to
Represents three alkyl groups or alkoxyl groups, and n is 0 to
Represents an integer of 3. )). Preferred examples of the dihalo aromatic compound include, for example,

Embedded image (Where X ₁ represents a halogen atom) or a mixture thereof, of which p-dichlorobenzene is particularly preferred. In the case of a mixture, the proportion of the para-form dihaloaromatic compound is preferably at least 85 mol%.

The polymerization reaction between the alkali metal sulfide and the dihalo aromatic compound is carried out in a polar solvent. As the polar solvent, amide solvents such as N-methyl-2-pyrrolidone (NMP) and dimethylacetamide, and sulfone solvents such as sulfolane are preferable.

In order to adjust the degree of polymerization between the alkali metal sulfide and the dihalide, it is preferable to add an alkali metal salt such as a carboxylic acid or a sulfonic acid, or an alkali hydroxide. Further, if necessary, 5 mol% or less of a trihalide such as trichlorobenzene may be added to the dihalide.

The polymerization reaction is carried out under an inert gas atmosphere at 180 ° C.
It is preferably carried out at a temperature of ~ 300 ° C for 2-10 hours. After completion of the polymerization reaction, the produced polymer is separated by filtration, sufficiently washed with deionized water, and dried to obtain PAS. PAS is not limited to a substantially linear polymer, and PAS having a crosslinked structure may be used as long as the thermal stability during melting is not significantly impaired.

(B) Acid treatment of PAS polymerization product It is preferable that the raw material PAS used in the present invention has been acid-treated. The acid treatment converts the molecular chain end of PAS from -SNa to -SH, and can increase the crystallization temperature and crystallinity of PAS. The acid may be either an organic acid or an inorganic acid. As the organic acid, for example, formic acid,
Acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, benzoic acid, phthalic acid, salicylic acid, acrylic acid, crotonic acid, oleic acid, oxalic acid, maleic acid, fumaric acid, and the like. As the inorganic acid, for example, hydrochloric acid, sulfuric acid,
Examples thereof include sulfurous acid, nitric acid, phosphoric acid, boric acid, and carbonic acid.
These acid salts can also be used. Of these, acetic acid and hydrochloric acid are preferred.

The PAS may be an acid treatment of the slurry after the completion of the reaction, or an acid treatment after filtering and purifying the PAS.

When the PAS slurry is acid-treated, the pH of the PAS slurry after the acid treatment is 7.0 to 11.0, preferably 7.
Add the acid to 5-10.0. The amount of the acid to be added may be such that the pH of the PAS slurry is 7.0 to 11.0 as described above, and depends on the type of the acid and the pH of the PAS slurry. hand,
It is 0.2 to 10 mol%, preferably 0.5 to 6.0 mol%.
When the acid is a liquid, it is added as it is or after being diluted with another solvent (for example, N-methylpyrrolidone), and when the acid is a solid, it is added by dissolving in an appropriate solvent (water, alcohol, N-methylpyrrolidone, etc.). The acid treatment temperature may be any temperature from room temperature to PAS polymerization reaction temperature, but is preferably from room temperature to 250 ° C. The acid treatment time is 5 minutes to 24 hours, preferably 20 minutes to 3 hours.

When PAS is filtered and purified and then treated with an acid, the PAS is separated and purified by a conventional method, and then treated in an acid solution at 100 ° C. or lower. As the solvent, water or a mixture of water and a small amount of a water-miscible organic solvent can be used. The concentration of the acid solution is preferably 0.01 to 5% by weight, and the pH at the end of the treatment is preferably 4 to 5. The temperature for the treatment with the acid solution is 100 ° C or lower, preferably 40 to 80 ° C. The processing time is 5 minutes to 2 hours, preferably 10 minutes to 1 hour.

(C) Characteristics of PAS The PAS thus obtained has a weight average molecular weight of 10,500 to 25,000, preferably 14,000 to 20,000, and
It has a crystallization temperature of 0-260 ° C, preferably 230-255 ° C. In addition, a flow tester (manufactured by Shimadzu Corporation, CFT-
300 ° C. using a 500C), the melt viscosity V ₆ measured after holding for 6 minutes under a load of ^{20kgf / cm 2, L / D} = 10 30
~ 290 poise, preferably 60-160 poise, more preferably 80-140 poise. If the melt viscosity V ₆ is less than 30 poise, yarn breakage is likely to occur in the course of melt spinning, more than 290 poise when spinnability fiber diameter becomes thick and reduced.

[2] Method for Producing Melt-Blow Nonwoven Fabric FIG. 1 shows a preferred apparatus for use in producing a melt-blown nonwoven fabric. The melt blown nonwoven fabric forming apparatus includes an extruder 1, a hopper 3 for supplying PAS to the extruder 1, a die 2 provided at a tip of the extruder 1, and a high-temperature air transport pipe 4.
And an air supply device 5 (only one is shown) connected to the die 2, an air heater 6, and a collector roll 7 provided at a predetermined position from the tip of the die 2.

FIG. 2 shows a cross section of the die 2. The die 2 includes an upper die plate 21, a lower die plate 22, an upper air plate 23, and a lower air plate 24. By combining these parts, the nozzle 10, the slits 11 and 12 for ejecting air, the upper air chamber 25 and the lower air chamber 26 communicating with the slits 11 and 12,
Are formed. The nozzle 10 is composed of a rear end, an intermediate portion, and a front end, and a PAS inlet 27 is connected to the rear end,
An intermediate portion is a resin chamber 28. The high-temperature air transport pipe 4 is connected to the upper air chamber 25 and the lower air chamber 26, respectively. The upper die plate 21 and the lower die plate 22 contain the nozzle 10
Heaters 13 and 14 for keeping the temperature at a predetermined temperature are embedded.

In the melt blown nonwoven fabric forming apparatus having such a structure, the PAS is supplied from the hopper 3 to the extruder 1, melted and kneaded, then flows into the resin chamber 28 of the die 2 through the inlet 27, and passes through the nozzle 10. Discharged. At this time, the discharged PAS in a molten state is converted into ultrafine fibers by high-temperature air injected at high speed from the slits 11 and 12. The formed ultrafine fibers 8 are accumulated on a collecting surface such as a rotating collector roll 7 to form a nonwoven fabric 9.

In such a production method, the melt spinning temperature of the PAS is preferably set to a temperature which is higher by about 30 to 100 ° C. than the melting point of the PAS. Specifically, the melt spinning temperature is set to 310-
At 380 ° C., unevenness in melt viscosity of PAS in the die and thickening due to excessive oxidative deterioration or cross-linking can be prevented, stabilization of spinning can be achieved, and a PS having an average fiber diameter of 0.1 to 30 μm can be achieved.
AS fiber is obtained.

For the die 2, the inner diameter of the nozzle 10 is 0.1
It is preferably from 1.0 to 1.0 mm, particularly preferably from 0.2 to 0.8 mm. The nozzle 10 is preferably maintained at a temperature of 280 to 400 ° C, particularly 310 to 380 ° C. If the temperature of the nozzle is lower than 280 ° C., the PAS is rapidly solidified immediately after being discharged from the nozzle, so that sufficient stretching (crystallization) does not progress, and the heat resistance (thermal shrinkage) of the obtained nonwoven fabric is reduced. Low. On the other hand, when the temperature exceeds 400 ° C., the single fibers are fused with each other in a wide range, and the fiber diameter tends to vary, which is not preferable.

The discharge amount of PAS from the nozzle 10 is preferably 0.1 to 1.5 g / min, particularly preferably 0.2 to 1.0 g / min per nozzle.

The temperature of the high-temperature air injected from the slit is preferably higher than the temperature of the nozzle 10 by 10 to 20 ° C., more preferably 290 to 420 ° C., and particularly preferably 320 to 40 ° C.
0 ° C. is preferred. If the temperature of the hot air is lower than 290 ° C,
Because the PAS solidifies immediately after leaving the nozzle 10,
Sufficient stretching (crystallization) does not progress, and the heat resistance (heat shrinkage) of the obtained nonwoven fabric is low. On the other hand, when the temperature exceeds 420 ° C., the single fibers are fused to each other in a wide range, and the fiber diameter tends to vary.

The injection amount of high-temperature air is 1 kg / hr PAS
30~100 Nm ³ / hr, and is preferably in particular 40 to 70 nm ³ / hr against. If the injection amount of the high-temperature air is small, the tensile strength of the formed fiber decreases, which is not preferable.
Further, the ejection pressure is preferably 0.2 to 1.0 kgf / cm ² G.

In order to stabilize the discharge of PAS, an inert gas such as nitrogen gas is introduced into the hopper 3 of the extruder to shut off oxygen to prevent thickening and oxidative crosslinking in the melt extrusion process. Is preferred.

The formed ultrafine fibers of PAS are continuously collected by the collector roll 7 while being entangled. The distance between the die 2 and the collector roll 7 is 5 to 100 cm, especially
Preferably it is between 20 and 50 cm. If the distance between the die 2 and the collector roll 7 exceeds 100 cm, the flow of the fibers is disturbed, and the fibers are completely solidified at the time of deposition, making it difficult to obtain a nonwoven fabric in which the fibers are sufficiently entangled. On the other hand, if it is less than 5 cm, the fusion between the fibers is too large. By such a production method, 10,000 to 20,000, preferably 1 to
A nonwoven fabric consisting of PAS fibers having a weight average molecular weight of 1,000 to 19,000 and a crystallization temperature of 220 to 260 ° C. is obtained. When the weight-average molecular weight is less than 10,000, only a low-strength nonwoven fabric can be obtained. When the weight-average molecular weight exceeds 20,000, the nonwoven fabric has a sufficient strength but has a large fiber diameter. By increasing the crystallization temperature to the above range, the crystallinity of the PAS fiber can be increased, and the strength and heat resistance of the nonwoven fabric can be improved.

The resulting melt-blown nonwoven fabric may be subjected to post-treatments such as heat setting with a heating roll, calendering, annealing, infrared irradiation, induction heating, and the like.

[3] Physical Properties of Meltblown Nonwoven Fabric The physical properties of the meltblown nonwoven fabric of the present invention comprising PAS are as follows:
Average fiber diameter of 0.5 to 30 μm, preferably 1 to 20 μm,
It is particularly preferably 1 to 15 μm, and the basis weight is 5 to
300 g / m ^2, preferably 5~150 g / m ^2, particularly preferably 5 to 50 g / m ^2. If the average fiber diameter is less than 0.5 μm, the orderly landing and lamination of the fibers during the melt-blowing spinning process are hindered, and the cut fibers fly into the air as fly, making it impossible to form a uniform nonwoven fabric. Also 50μ
When it is more than m, for example, the aperture for use in a filter becomes large, and the performance as a filter decreases, which is not preferable.

[0037]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto.

Synthesis Example 1 Production of polyarylene sulfide (PAS-1) In an autoclave (capacity 200 liter) equipped with an electromagnetic induction stirrer, 72.0 kg of N-methylpyrrolidone, 37.2 kg (240 mol) of sodium sulfide 2.7 hydrate were added. And 112 g (2.8 mol) of sodium hydroxide at 211 ° C. under a nitrogen atmosphere.
The temperature was raised over 2 hours until 31.2 kg of the generated distillate was distilled off. Then, 36.0 kg of p-dichlorobenzene (p-DCB) (24
4.9 mol) and 20 kg of N-methylpyrrolidone.
The temperature was raised to 5 ° C., and a polymerization reaction was carried out for 3 hours while stirring.
When the temperature in the reaction system reached 255 ° C, water was sprinkled on the upper part of the reactor and cooled.

After the completion of the polymerization reaction, the temperature in the reaction system is set to 150 ° C.
At that time, an aqueous solution of hydrochloric acid was added to adjust the pH in the system to 7.0, followed by stirring at 150 ° C. for 30 minutes. Cool further,
When the temperature in the reaction system reached 120 ° C., the polymerization slurry was filtered. The filtered slurry was flushed under reduced pressure to remove N-methylpyrrolidone and then washed seven times with 120 liters of warm water. Heat and dry at 120 ° C for 12 hours.
24.1 kg of polyarylene sulfide (PAS-1) was obtained.
The yield based on sodium sulfide was 93%.

Synthesis Example 2 Preparation of polyarylene sulfide (PAS-2) 24.6 kg of polyarylene sulfide (PAS-2) was prepared in the same manner as in Synthesis Example 1 except that the amount of p-dichlorobenzene added was 36.4 kg (247 mol). -2) Got it. The yield based on sodium sulfide was 95%.

Synthesis Example 3 Production of polyarylene sulfide (PAS-3) Polyarylene sulfide (PAS-2) obtained in Synthesis Example 2
Was placed in a hot air circulating oven set at 230 ° C and treated for 3 hours to obtain semi-crosslinked polyarylene sulfide (PAS-
3) Got it.

Comparative Synthesis Example 1 Preparation of polyarylene sulfide (PAS-4) 24.6 kg of polyarylene sulfide (PAS-4) was prepared in the same manner as in Synthesis Example 1 except that an aqueous hydrochloric acid solution was not added after the completion of the polymerization reaction. Obtained. 95% yield based on sodium sulfide
Met.

Comparative Synthesis Example 2 Preparation of polyarylene sulfide (PAS-5) 23.6 kg of polyarylene sulfide (PAS-5) was prepared in the same manner as in Synthesis Example 1 except that the amount of p-dichlorobenzene added was 35.3 kg (240 mol). PAS-5). The yield based on sodium sulfide was 91%.

The polyarylene sulfide obtained in Example 1 Synthesis Example 1 (PAS-1
) Was introduced into the twin-screw extruder of the melt-blown nonwoven fabric forming apparatus shown in FIG. 1 and melted and kneaded.
The nozzles are fed to 300 dies in a row at an interval of mm, the nozzle temperature is set to 330 ° C, and a high-temperature air flow (temperature of 350 ° C, pressure of 1.0 kgf / cm) is output at 0.5 g / min.
During ² G), discharged at the rate of hot air / resin weight = 50/1 to form a fine fiber of polyarylene sulfide.
So that the basis weight of the obtained nonwoven fabric is 50 g / m ² ,
The rotation speed of the collector roll 30 cm away from the die was adjusted, and the formed fine fibers were continuously collected to obtain a melt-blown nonwoven fabric. Weight average molecular weight (Mw), crystallization temperature (Tc) and melt viscosity (V) of PAS fibers forming a nonwoven fabric
₆ ) was measured by the following method, and the tensile strength and average fiber diameter of the obtained meltblown nonwoven fabric were measured by the following method. The results are shown in Table 1.

(1) Weight-average molecular weight (Mw): SSC-7000 manufactured by Senshu Kagaku Co., Ltd. was used as a measuring device, 1-chloronaphthalene was used as a mobile phase, and the retention time at 210 ° C. was determined by gel permeation chromatography. Was measured, converted to a standard polystyrene molecular weight, and further corrected by a universal calibration method.

(2) Crystallization temperature (Tc): Using a differential scanning calorimeter (SSC5200, manufactured by Seiko Denshi Kogyo KK), 10 mg of polyarylene sulfide was heated in a nitrogen stream at a heating rate of 20 ° C.
/ Min after heating to 320 ° C and melting for 5 minutes, then measuring the exothermic peak temperature when cooling at 10 ° C / min,
The crystallization temperature (Tc) was used.

(3) Melt viscosity (V ₆ ): Using a flow tester (CFT-500C, manufactured by Shimadzu Corporation), polyarylene sulfide was used at 300 ° C., load 20 kgf / cm ² , L / D = 10.
After holding for 6 minutes under the above conditions, the measurement was performed.

(4) Tensile strength (kg / 5 cm): Using a test piece of 20 cm length × 5 cm width, the chuck interval was adjusted to 10 cm, and the tensile strength was measured at room temperature with an autograph tensile tester.

(5) Average fiber diameter: Ten arbitrary points on the test piece were selected, and one photograph was taken at each point, and a photograph was taken with an electron microscope at a magnification of 2000 times. Any 10 for each photo, total
The diameter of 100 fibers was measured and the average was calculated.

[0050] As Examples 2 polyarylene sulfide, except using PAS-2, PAS-3 obtained in Synthesis Example 2 to produce a melt-blown nonwoven fabric in the same manner as in Example 1, forming a non-woven fabric P
AS fiber weight average molecular weight, crystallization temperature and melt viscosity,
The tensile strength and average fiber diameter of the nonwoven fabric were measured. The results are shown in Table 1.

Comparative Examples 1 and 2 Melt blown nonwoven fabrics were produced in the same manner as in Example 1 except that PAS-4 and PAS-5 obtained in Comparative Synthesis Examples 1 and 2 were used as polyarylene sulfides. The weight average molecular weight, crystallization temperature and melt viscosity of the formed PAS fiber, as well as the tensile strength and average fiber diameter of the nonwoven fabric were measured. The results are shown in Table 1.

Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Resin PAS-1 PAS-2 PAS-3 PAS-4 PAS-5 Weight average molecular weight Mw 18,000 14,000 19,000 18,500 31,500 Crystallization temperature Tc ( ° C) 238 241 253 218 233 233 Melt viscosity V ₆ (poise) 120 60 140 130 560 Tensile strength (kg / 5cm) 4 3.5 6 2 10 Average fiber diameter (μm) 8 5 12 15 35

As is apparent from Table 1, the melt-blown nonwoven fabrics of polyarylene sulfide of Examples 1 to 3 had an extremely fine fiber diameter and good tensile strength.

[0054]

As described in detail above, the weight average molecular weight is
10,000-20,000 and crystallization temperature of 220-260 ° C
The melt-blown nonwoven fabric of the present invention comprising the polyarylene sulfide fiber of the present invention has an extremely fine fiber diameter and good tensile strength.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an apparatus for producing a melt blown nonwoven fabric from polyarylene sulfide.

FIG. 2 is a longitudinal sectional view of a die of the apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Extruder 2 ... Die 3 ... Hopper 4 ... High-temperature air transport pipe 5 ... Air supply device 6 ... Air heater 7 ... Collector roll 8 ... Fine fiber 9・ ・ ・ Melt blow non-woven fabric 10 ・ ・ ・ Nozzle 11,12 ・ ・ ・ Slit 13,14 ・ ・ ・ Heater 21,22 ・ ・ ・ Die plate 23,24 ・ ・ ・ Air plate 25,26 ・ ・ ・ Air chamber 27 ・..Inlet 28 ... Resin chamber

Claims (3)

[Claims] 1. A melt-blown nonwoven fabric comprising a polyarylene sulfide fiber having a weight average molecular weight of 10,000 to 20,000 and a crystallization temperature of 220 to 260 ° C. 2. The melt-blown nonwoven fabric according to claim 1, wherein the basis weight is 5 to 300 g / m ² and the average fiber diameter is 0.5 to 30 μm. 3. The method for producing a melt-blown nonwoven fabric according to claim 1, wherein (a) melt-kneading the polyarylene sulfide, and (b) discharging from a nozzle set at 280 to 400 ° C. and 290 to 420 ° C. (C) accumulating the obtained fibers in a collecting section.