JPH09157943A - Fine porous fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fine porous fiber having small porosity and average fine pore diameter, large specific surface area, excellent in absorbing perfor mance and having large strength, especially extremely suitable for liquid/liquid separating material. SOLUTION: This fine porous fiber is obtained by forming a composition comprising 65-85wt.% polyolefin and 15-35wt.% synthetic polymer particles having <=1.0μm average particle diameter, e.g. a silicone resin such as polymethylsilsesquioxane in fibrous state and then drawing the fiber at 2-8 draw ratio. The fiber has a fine porous structure comprising through holes having 0.01-0.1μm average pore diameter and the fiber has 10-25% porosity and 65-100m<2> /g specific surface area.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel polyolefin-based microporous fiber. Specifically, it is composed of a polyolefin composition containing specific synthetic polymer particles,
It is a high-strength microporous fiber having a microporous structure with an extremely large specific surface area. In particular, the present invention provides a microporous fiber which is useful as a thread for a cartridge filter for liquid-liquid separation utilizing surface adsorption due to a large specific surface area.

[0002]

2. Description of the Related Art In recent years, functionalization of fibers has been studied and put into practical use for various fibers. One of them is microporous fiber.

For example, in Japanese Patent Laid-Open No. 4-18112, a paraffin wax is kneaded into a polyolefin, which is spun and stretched, and then the paraffin wax is extracted and removed using an appropriate solvent and further dried. Describes a method for obtaining microporous fibers. By such a method, it is possible to obtain good microporous fibers having uniform microporosity.

[0004]

However, the microporous fiber obtained by the known method as described above has a specific surface area of about 10 m ² / g, and the surface adsorptivity of the microporous fiber described above is utilized. In the application for liquid-liquid separation,
There was still room for improvement.

However, in the above method, in order to increase the specific surface area, it is necessary to increase the amount of paraffin wax and increase the porosity formed by the extracted paraffin wax. When the porosity is increased, the strength is lowered, and there is a possibility that the handling property when wound into a cartridge is deteriorated.

Therefore, it has micropores effective for adsorption,
Moreover, while having a high specific surface area due to the microporosity,
The development of microporous fibers that maintain high strength is desired.

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies for the purpose of developing a novel microporous fiber having the above-mentioned characteristics.

As a result, a specific synthetic polymer particle is melt-mixed with polyolefin in a specific amount to form a fiber, and the fiber is stretched under specific conditions to obtain a specific pore diameter and a large specific surface area which has never been obtained. The present inventors have succeeded in obtaining a microporous fiber having a small porosity and a high strength and satisfying all the above objects, and have completed the present invention.

That is, the present invention relates to a polyolefin (hereinafter,
65 to 85% by weight, the average particle size is 1 μm.
The following synthetic polymer particles (hereinafter referred to as component b) 15
~ 35% by weight, average pore size 0.01-0.1μ
It has a microporous structure consisting of m communicating holes and has a porosity of 1
It is a microporous fiber having 0 to 25% and a specific surface area of 65 to 100 m ² / g.

In the present invention, known polyolefins can be used as the component a without particular limitation.
For example, polyethylene, polypropylene, polybutene
1 or a homopolymer of α-olefin such as polymethylpentene, a copolymer of α-olefin and another copolymerizable monomer, and a mixture thereof.
Among them, homopolymers of propylene, copolymers of propylene with other copolymerizable monomers, and mixtures thereof are preferable in consideration of heat resistance and moldability of the obtained microporous fiber.

The copolymer of the above-mentioned α-olefin and another copolymerizable monomer generally contains at least 90% by weight of α-olefin, particularly propylene, and at most 10% by weight of another copolymerizable monomer. Copolymers are preferred. The copolymerizable monomer is not particularly limited, and known monomers can be used, but α-olefins having 2 to 8 carbon atoms, particularly ethylene and butene are generally preferable. In the present invention, as the component b, known synthetic polymer particles can be used without particular limitation, but it is preferable to select one that does not cause aggregation when mixed with a polyolefin and is uniformly dispersed. Such synthetic polymer particles are used in the stretching step to cause separation at the interface between the polyolefin and the dispersed synthetic polymer particles to form fine communication holes.

The synthetic polymer particles used in the present invention are thermosetting resins and thermoplastic resins, so-called vinyl-based cross-linked polymers and the like obtained by the sol-gel method as long as they exhibit the above-mentioned functions. Known synthetic polymer particles such as polymer particles of silicic acid having a group can be used. If the decomposition temperature is below the molding temperature of the polyolefin, it cannot be made microporous.

Specific examples of the synthetic polymer particles which can be preferably used in the present invention include 6-nylon,
Polyamide such as 6,6-nylon; Fluorine-based resin such as polytetrafluoroethylene, tetrafluoroethylene-propylene hexafluoride copolymer; polyimide; silicone resin; phenol resin; benzoguanamine resin; or styrene, acrylic acid, A copolymer of methacrylic acid, methyl acrylate, methyl methacrylate and the like and a crosslinking agent such as divinylbenzene is suitable. Of these, silicone resin particles are preferably used in the present invention because they have good interfacial peelability from polyolefins and can be easily made porous by stretching.

The average particle size of the above synthetic polymer particles is
It must be 1.0 μm or less. When the average particle diameter of the synthetic polymer particles is larger than 1.0 μm, the moldability into fibrous form becomes poor, the average pore diameter of the obtained fiber is large, and the specific surface area is not large, which is not preferable. The average particle size of the synthetic polymer particles for obtaining suitable microporous fibers is 0.03 to 0.5 μm.

The narrower the particle size distribution of the above synthetic polymer particles, the more uniform the fine pores can be obtained, which is preferable. Generally, when the particle size distribution is expressed as a dispersion, the dispersion is preferably 1.5 or less, more preferably 1.0 or less. Further, the shape of the above-mentioned synthetic polymer particles may be any shape, but it is usually a spherical shape or an elliptical shape in which the ratio of the major axis to the minor axis is in the range of 1 to 2 so that the diameter is uniform. It is preferable because various fine pores can be obtained. The above ratio is preferably in the range of 1 to 1.5.

The ratio of the a-component polyolefin to the b-component synthetic polymer particles is from 65 to 85% by weight, preferably from 65 to 80% by weight, and from 15 to 3% by weight for the b component.
It is 5% by weight, preferably 20 to 35% by weight. The a
The composition ratio of the component and the component b is important for keeping the properties of the microporous fiber within the above specific range and for producing the microporous fiber industrially advantageously in the production method described later. If the proportion of the b component is less than the lower limit value, the pore formation of the microporous fiber obtained is not sufficient, and conversely b
If the addition ratio of the component is more than the above upper limit, there is a tendency that the moldability of the fiber deteriorates, or the stretching cannot be sufficiently performed, and in any case, the average pore diameter, the porosity and the specific surface area of the present invention. Can't be satisfied.

It may be difficult to mix the component a with the component b in a large amount and uniformly. In such a case, a specific amount of a dispersant is added when the component a and the component b are mixed. Preferably. That is, the a component and b
The dispersant is 0.1 to 100 parts by weight based on the total amount of the components.
It is preferable to add 20 parts by weight to obtain a good microporous fiber.

As the dispersant, a known compound added as a plasticizer to various synthetic resins can be used without particular limitation. Generally used dispersants are polyester plasticizers,
It is an epoxy plasticizer and polybutadiene with OH terminal.
Examples of these are as follows.

The above polyester plasticizers are generally esterified from a dibasic acid or tribasic acid having a linear or aromatic ring having 4 to 8 carbon atoms and a linear dihydric alcohol having 2 to 5 carbon atoms. Those reacted are preferable. Specific examples of particularly preferably used ones include dibasic acids or tribasic acids such as sebacic acid, adipic acid, phthalic acid, azelaic acid and trimellitic acid, and ethylene glycol, propylene glycol, butylene glycol. equal,
A polyester compound consisting of neopentylglycol and long-chain alkyleneglycol, and particularly preferably a polyester compound consisting of adipic acid or sebacic acid and propyleneglycol, butyleneglycol or long-chain alkyleneglycol.

The epoxy plasticizer has 8 to 24 carbon atoms.
Those obtained by epoxidizing the double bond of the monobasic linear unsaturated acid are preferred. Particularly preferably used are epoxidized soybean oil and epoxidized linseed oil, which can be used alone or in combination.

As the OH-terminated polybutadiene, those obtained by hydroxylating both ends having a polymerization degree of 500 to 2000 are preferably used.

The addition ratio of the above-mentioned dispersant is 0.5 to 1
It is 0% by weight, preferably 1 to 5% by weight. If the proportion of the dispersant is less than the lower limit, microporosification of the obtained fiber is not sufficient, and conversely, if the proportion of the dispersant added is more than the upper limit, the moldability of the fiber is deteriorated,
It is not preferable because there is a tendency that stretching cannot be performed sufficiently.

The microporous fiber of the present invention has an average pore diameter of 0.01 to 0.10 μm, preferably 0.01 to 0.0.
5 μm, porosity 10-25%, preferably 15-25
%, Specific surface area of 65 to 100 m ² / g, preferably 65
８０80 m ² / g.

Conventionally, various microporous fibers have been proposed, but the microporous fiber having such a high specific surface area in terms of average pore diameter and porosity as described above was first proposed in the present invention. is there. The microporous fiber of the present invention has excellent adsorption properties based on such specific surface area while maintaining high strength.

In the present invention, the average pore diameter, porosity and specific surface area are values measured by the mercury porosimetry method.

The average pore diameter is 0.01 to 0.10 μm
When the value is out of the range, it is difficult to adjust the specific surface area and the porosity to the above range without sacrificing the strength.

When the porosity is less than 10%, the strength is increased, but the specific surface area is decreased and the adsorption performance is deteriorated.
The larger the strength, the lower the strength. The specific surface area is 6
If it is less than 5 m ² / g, the adsorption performance becomes insufficient and 10
When it is larger than 0 m ² / g, the porosity is also chained to 2
Since it exceeds 5%, the strength becomes low, which is not preferable.

The microporous fiber of the present invention has a small average pore diameter of 0.01 to 0.10 μm and a specific surface area of 65 to 1
Since it has a large value of 00 m ² / g, it has excellent adsorption performance, and has a feature that it has a large strength because it has a small porosity of 10 to 25%.

The fiber diameter of the microporous fiber of the present invention is not particularly limited, but the diameter is generally in the range of 10 μm to 30 μm.

The method for producing the microporous fiber of the present invention is not particularly limited. A typical production method is as follows: polyolefin 65 to 85% by weight, average particle size 1
A microporous fiber can be obtained by melt-molding a mixed composition of 15 to 35% by weight of synthetic polymer particles having a particle size of not more than μm into a fibrous material under specific conditions described below and then stretching.

Upon mixing the above components, a colorant, a lubricant, and a colorant are added as long as they do not interfere with the production of the target microporous fiber.
It is often a good practice to add known additives such as antioxidants, deterioration inhibitors, hydrophilizing agents, hydrophobizing agents and the like.

The above-mentioned mixed composition can be easily and uniformly mixed by using a known mixer such as an ordinary super mixer or Henschel mixer, and then melt pelletized by an ordinary single-screw or twin-screw extruder.

A microporous fiber can be obtained by melt-molding the above-mentioned mixed composition into a fibrous material under specific conditions to obtain an unstretched fiber and then stretching.

The method for molding the above composition into a fibrous form is not particularly limited, but generally, an unstretched fiber can be obtained by using a known extruder equipped with a nozzle. in this case,
The draft ratio controlled by the extrusion rate and the take-up speed during spin molding of unstretched fibers is calculated by the following formula, and is generally 150-
It is desirable to determine in the range of 1000, preferably 150 to 800.

[0035]

(Equation 1)

In particular, the take-up speed that determines the draft ratio is
It is important to achieve a high specific surface area of the microporous fibers obtained in the subsequent drawing, and it is desirable to select a speed of 190 to 900 m / min.

The unstretched fiber obtained by the above method is generally stretched by a uniaxial stretching method or the like depending on the difference in rotation speed ratio between two pairs of Nelson rolls and godet rolls.

The draw ratio for obtaining the microporous fiber of the present invention is not particularly limited, but is generally 2 to 8 times, preferably 3 to 6 times. If the stretching ratio is small, the generation of fine pores is not sufficient and the specific surface area is small, resulting in poor adsorption performance. Conversely, if it is too large, the frequency of cutting during stretching increases and manufacturing problems increase.

The stretching temperature is generally from room temperature to the melting point of the polyolefin, and preferably 10 to 100 ° C. lower than the melting point. Stretching temperature is 10 ° C higher than the melting point of polyolefin
At a low temperature or higher, stretching can be easily performed, but the formation of microporosity is not sufficient, or the generated microporosity is undesirably crushed by heat, and conversely, at a stretching temperature 100 ° C or more lower than the melting point of polyolefin, The desired stretching ratio cannot be achieved, and the frequency of cutting increases, which is not preferable.

The microporous fiber obtained by the above stretching may be further heat treated under tension, for example, heat set at a temperature not lower than the stretching temperature but not higher than the melting point, and then cooled to room temperature to obtain the desired product. preferable. In addition, it is a preferable embodiment to perform a surface treatment such as a corona discharge treatment, a hydrophilic treatment, or a hydrophobic treatment for the purpose of improving the adhesiveness.

[0041]

As described above, the microporous fiber obtained in the present invention is made of polyolefin having excellent heat resistance, chemical resistance, biocompatibility and strength, and has an average pore diameter of 0.01 to. 0.10 μm and specific surface area of 65 to 10
A microporous fiber having a large strength of 0 m ² / g and a small porosity of 10 to 25% can be provided.

Therefore, the microporous fiber obtained by the present invention is an air filter for removing dust and bacteria; wastewater treatment; production of clean water in the food industry, electronic industry, pharmaceutical industry; various liquid / liquid separations, etc. It is preferably used for a material for a cartridge filter used in, and further as a support for microfiltration, ultrafiltration, pervaporation and the like. Further, it can be considered to be used as a fiber for clothes having good air permeability and a filter cloth non-woven fabric due to its large specific surface area.

[0043]

EXAMPLES In order to explain the present invention more specifically, the following will be described.
Examples and comparative examples will be described below, but the present invention is not limited to these examples. The physical properties and judgments of the microporous fibers shown in Examples and Comparative Examples are the values measured or judged by the following methods.

(1) Average pore diameter (μ): Measured by a mercury porosimetry method using a pore sizer 9310 manufactured by Shimadzu Corporation.

(2) Specific surface area (m2 / g): Measured by a mercury porosimetry method using a pore sizer 9310 manufactured by Shimadzu Corporation.

(3) Porosity (%): Measured by a mercury porosimetry method using a pore sizer 9310 manufactured by Shimadzu Corporation.

(4) Diameter (μm); Hylox Corporation
The measurement was performed using a micro high scope system DH-2200 manufactured by KK.

(5) Denier (g / 9000 m); The weight of fiber per 9000 m of length was measured.

(7) Elongation (%): Using a tensile tester Autograph 200 manufactured by Shimadzu Corporation, sample length 100 m
m, at a tensile speed of 300% / min.

(8) Breaking strength (g / d); using Autograph 200 manufactured by Shimadzu Corporation, sample length 100 m
m, at a tensile speed of 300% / min.

(9) Young's modulus (g / d); using Autograph 200 manufactured by Shimadzu Corporation, sample length 100 m
m, at a tensile speed of 300% / min.

(10) Adsorption amount: 1 g of fiber was added to a 1: 1 mixed solution of isopropyl alcohol (reagent) and distilled water.
After immersion for a time, the amount of the solution to which the fibers were adsorbed was calculated from the weight change.

(11) Formability: The unstretched fiber was visually and manually touched to observe and judged according to the following criteria.

Good; thickness unevenness, no surface irregularities somewhat good; thickness unevenness, or one of the surface irregularities is minute Bad: uneven thickness, uneven surface (12) Dispersibility; The microporous fiber obtained by stretching was visually inspected and judged by the presence or absence of fish eyes.

Good: No fisheyes Slightly good: Very fine fisheyes observed Poor: Fisheyes observed (13) Stretchability: Judged by the stretched state when stretching unstretched fibers did.

Good; state in which cutting and tearing did not occur and stretching was carried out uniformly Slightly inferior; state in which some unstretched portions exist even after stretching was possible Stretching was not possible; cutting and tearing occurred and stretching A state in which it is not possible to carry out Examples 1 to 11 and Comparative Examples 1 to 5 2% by weight dispersion based on 100 parts by weight of the total amount of polyolefin, synthetic polymer particles, and polyolefin and synthetic polymer particles as shown in Table 1. After mixing the composition consisting of the agents with a super mixer for 5 minutes, 170
It was extruded into strands at ~ 230 ° C and cut into pellets.

[0057]

[Table 1]

The pellets obtained were screwed with a screw diameter of 40 m.
0.7 m in diameter attached to an extruder with mφ and L / D = 22
230 from a fiber manufacturing nozzle with 198 m holes
It was extruded at ˜300 ° C., put into an air-cooled ring to be cooled, and taken out at 200 to 890 m / min to obtain an unstretched fiber. This unstretched fiber was uniaxially stretched between two pairs of seven-constituting godet rolls having different rotation speeds at 150 ° C. at a stretch ratio of 3 to 6 to obtain a microporous fiber. The respective conditions are as shown in Table 2.

[0059]

[Table 2]

The following products were used as the polyolefin, synthetic polymer particles and dispersant used.

Polyolin; polypropylene; PN-120 (trade name) manufactured by Tokuyama Corp.
Polyethylene with an intrinsic viscosity of 2.38 dl / g and a melting point of 166 ° C. measured with tetralin having a density of 0.91 g / cm ³ and 135 ° C .; Mitsui Petrochemical Co., Ltd., high-density polyethylene high-dex 1300J (trade name), melt index 1.
3 g / 10 min Synthetic polymer particles; Polymethylsilsesquioxane (A); Toray Silicone Co., Ltd., Trefil R-935 (trade name), spherical particles having an average particle diameter of 4 μm, dispersion 1.5 Polymethylsilsesquioxane ( B); Toray Silicone Co., Ltd., Trefil R-935 (trade name), spherical particles having an average particle size of 0.5 μm, dispersion 0.007 benzoguanamine; Nippon Shokubai Kagaku Kogyo Co., Ltd., Eposter RL (commodity) Name), spherical particles having an average particle diameter of 15 μm,
Dispersion 0.3 N-phenylmaleimide-styrene-divinylbenzene; obtained by radical polymerization in n-hexane 0.1-0.
2 μm Synthetic Polymer Particle Dispersant: Nippon Soda Co., Ltd., OH-terminated polybutadiene, GI-1000 (grade name) The physical properties of the fiber obtained by the above method are shown in Table 3.
As a result of examining the adsorbed liquid in the adsorption amount test of each example, it was confirmed that most of the adsorbed liquid was isopropyl alcohol and that the alcohol was selectively adsorbed.

[0062]

[Table 3]

Claims (1)

[Claims] 1. A microporous structure comprising 65 to 85% by weight of polyolefin and 15 to 35% by weight of synthetic polymer particles having an average particle diameter of 1 μm or less, and having continuous pores having an average pore diameter of 0.01 to 0.1 μm. Microporous fibers having a porosity of 10 to 25% and a specific surface area of 65 to 100 m ² / g.