JPH0364577A - Aggregate of high-functionality ultrafine conjugate fiber and its production - Google Patents

Abstract

PURPOSE:To obtain an aggregate of high-functionality ultrafine conjugate fiber capable of collecting metallic ion in high efficiency and composed of a nonwoven fabric having a specific apparent density by introducing a specific graft part having amidoximated functional group into a skeleton fiber having a specific diameter. CONSTITUTION:A fiber aggregate having an apparent density of 0.1-0.5g/m<3> and composed of skeleton fibers having an average diameter of <=5mum is produced e.g. by melt-blow process and irradiated with ionizing radiation. The irradiated aggregate is graftpolymerized with acrylonitrile monomer and >=50wt.% of the skeleton fiber is amidoximated to obtain the objective aggregate of high-functionality ultrafine conjugate fiber containing introduced functional group and having high durability. The aggregate can collect metallic ion in high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a highly functional ultrafine conjugate fiber aggregate that can be used to collect metal ions.

=1- [Prior art] Modifying fibers to collect and remove ions in water or air, especially heavy metal ions that are not safe for safety reasons, or collecting metal ions needed for industrial purposes. This has already been attempted, but the collection efficiency was not sufficient. For example, methods for recovering metal ions using adsorbents with amidoximated groups are described in J. Okamoto and
others, J. Appl, Po1. Sci.

30, 2967 (1985), H, 0m1chia
nd others, Sep, Sci.

Technol, + 2 (L 163 (1985),
H,0m1chi and others.

Ib1d,, 21.299 (1986) Japanese Patent Publication No. 1973
JP-A-126088, JP-A-58-205543, JP-A-58-205544, etc. For fabrics containing ion-exchange fibers supported by ion exchangers, JP-A-62276049, JP-A-Sho. No. 62-298359 and the like are known.

[Problem to be solved by the invention]

Attempts to actively collect and recover ions from solutions such as lake/river water, seawater, domestic wastewater, industrial water/wastewater, etc., or to collect and remove ions from fibers and resins funded by government funds. , films, etc. have already been tried, but because they use materials found in the prior art, the collection effect is not sufficient, and these fibers,
Resin and film did not have sufficient strength under the usage conditionsb
Therefore, its practicality was insufficient. An object of the present invention is to provide a highly functional ultrafine conjugate fiber aggregate that has high collection efficiency and is durable.

[Means to solve the problem]

The present invention consists of fibers having an average diameter of 5 μm or less and a graft portion having amidoximated functional groups of 50 or more than the weight of the skeleton fibers, and an apparent density of 0.1.
It is a highly functional ultrafine conjugate fiber aggregate having an average particle diameter of 0.5 s+/ctA.

In addition, the present invention manufactures a fiber aggregate consisting of skeletal fibers with an average diameter of 5 μm or less, irradiates it with @female radiation, and uses a monomer that contains a nitrile group and can convert the nitrile group to an amidoxime group. This is a method for producing a highly functional ultrafine conjugate fiber aggregate by graft polymerizing the fibers of the aggregate and converting the nitrile groups into amidoximes.

In order to efficiently collect metal ions using a functional fiber aggregate of a certain weight and volume, the surface area is increased by using ultrafine fibers, which are converted into amidoximes and have a large number of functional groups. It is essential to do so. It has already been stated in extensive literature that the surface of #a fiber is an important point. According to the method mainly described in the present invention, when a special spinning method is used, ultrafine fibers with a large surface area and aggregates thereof can be simultaneously produced extremely efficiently.

The average diameter of the fibers used in the present invention is 5 μm or less. If it becomes very thin, the amount of amidoxime groups per fiber 17 will increase, but the density of the nonwoven fabric will be high and the housing will be good. A known method can be used to produce the ultrafine skeletal fibers used in the present invention. For example, the first method is to extrude a synthetic resin little by little through a fine nozzle hole and wind it up at high speed, but the problem is that the productivity is low. Father, second method 4- As a method, two or more synthetic polymers having mutually different solubility are used to fabricate sea-island structure fibers a'f, 9. There is a method of making bridge-fine fibers by leaving ultra-fine fibrous component A to remove the sea component, but the disadvantage is that it requires a special die and special processing such as removing the sea component, making it expensive. It is possible to make the polar Ifa fibers obtained by the first method into a non-woven fabric using known methods, but it is quite difficult, and the fiber thickness is limited to about 10 μm, and those thicker than that can be made by hydroentanglement. additional steps are required. In the second method, it is necessary to prepare a web from the sea islands 1 and fibers, and then remove the sea component with a solvent to obtain an ultrafine fiber aggregate.

Although it is possible to make ultrafine fiber aggregates using the existing methods described above, the melt blown method is effective for obtaining ultrafine fibers more efficiently. This method is the most desirable method for forming the ultrafine fiber aggregate that is the base material of the present invention, since a nonwoven fabric-like fiber aggregate made of fibers can also be produced at the same time.

5. The melt-blown method here refers to melt-extruding a thermoplastic polymer, discharging it from a multi-hole orifice nozzle, and simultaneously blowing it out with high-temperature, high-speed gas ejected from a gas ejection hole or groove adjacent to the nozzle. A nonwoven fabric-like ultrafine fa fiber aggregate is obtained by collecting the ultrafine fiber stream on a belt conveyor-like or drum-like collector. - For boat fishing, JP-A-49-10258, JP-A-49-48921
No. 50-121570, it is known as the melt blow method, JP 50-46972, the melt blow molding method, and JP 44-25871, the jet spinning method. .

According to the melt-prone method used in the present invention, the average diameter is 5
Fibers smaller than μm can be easily produced.

Any thermoplastic synthetic polymer may be used, including polyethylene, polypropylene, polybutene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyester acrylate, polystyrene, or copolymers thereof, and polystyrene. (ethylene-vinyl alcohol) copolymer, poly(tetrafluoroethylene-ethylene) copolymer, polyamide, polyester, polyurethane elastomer, etc. can be used. Among these, polypropylene is a desirable synthetic polymer because of its ease of forming radicals against the radiation used in the graft polymerization of the method of the present invention, radical stability, hydrophobicity as a skeleton fiber, and heat resistance.

Of course, the ultrafine fiber aggregate that serves as the base material of the present invention can be produced by methods other than the conventional melt-prone method described above.
These methods have already been applied to methods for producing nonwoven fabrics.

As already mentioned, conventionally, skeletal fibers have a diameter of 5 μm or more, especially ordinary fibers have a diameter of 15 μm or more, and sometimes 40 μm to 2 μm.
00 μm fibers have been used. This is easy to obtain,
Ease of processing when used as a skeletal fiber and processed into products such as cloth, morphological stability of textile products when modified graft fibers are used for long periods of time in acid/alkali, high temperature, ultraviolet light, etc. 7- This seems to be due to consideration of the above, but as described in the present invention, according to the method of the present invention, aggregates of ultrafine fibers of 5 μm or less were easily obtained, and there were no grafting problems.

In the case of the melt-blown method, the apparent density of the fiber aggregate is determined by the distance between the discharge nozzle and the collection belt conveyor, the amount of thermoplastic resin discharged per unit time, the moving speed of the belt conveyor, and the pressing conditions after collection. It is easy to adjust to υ.

Although it varies depending on the grafting conditions, the apparent density of the skeleton fiber aggregate is preferably in the range of 0.03 f/- to 0.25 f/-. If it is smaller than 0.03 f/cTA, the amount of fibers will be too small and the amount of functional groups after grafting and modification will be insufficient and an efficient composite fiber aggregate will not be obtained. When used underwater after denaturation, the resistance to flow increases, resulting in inefficiency.

- The apparent density referred to in the present invention is calculated by measuring the weight of the unit image 8i and dividing this value by the thickness. Thickness is JIS L
Measured using the 1096 method.

In the present invention, the ultrafine skeletal fiber aggregate thus obtained contains a nitrile group, is grafted with a monomer capable of converting the nitrile group into an amidoxime group, and is converted into an amidoxime. It can be made into a functional ultrafine composite fiber aggregate. These monomers include:
For example, acrylonitrile, vinylidene cyanide, crotonitrile, methacrylaterile, chloroacrylonitrile, 2-cyanoethyl acrylate, 2-cyanoethyl methacrylate, etc. can be used singly or in combination of two or more.

It is generally practical to use readily available acrylonitrile.

A preferred method for grafting is to irradiate the skeletal fiber aggregate with ionizing radiation in the presence of an inert gas such as kiln, followed by a grafting reaction. 1M,
The generation of homopolymers can be suppressed by introducing monomers after irradiation with dissociative radiation, but the generation of peroxide radicals can also be prevented by irradiation under an inert gas, which results in the generation of peroxide radicals during graft polymerization. The formation of homopolymers can be minimized. fii Dissociative radiation includes alpha rays, beta rays, r rays, XM, accelerated electron beams, etc. Skeletal fibers are irradiated with accelerated electron beams from an electron beam generator to create active radicals on the skeletal fibers and graft them. It is practical to use it as the starting point for polymerization. The irradiation dose can be determined depending on the grafting conditions, but in general, increasing the amount of radicals and increasing the number of graft polymerization initiation sites with a large dose of irradiation is the best way to efficiently create a highly functional ultrafine composite fiber aggregate. Preferably 1 Mrad or more, preferably 5 Mrad
As described above, irradiation of 50 Mrad or less is required. If the irradiation dose is too large, it will cause deterioration of the skeletal fibers and require a large amount of energy for irradiation, which is impractical.

After irradiation with ionizing radiation, a grafting reaction of a monomer containing a nitrile group and capable of converting the nitrile group into an amidoxime group is carried out in the gas phase or in the liquid phase under nitrogen. The grafting reaction is carried out until the grafting rate reaches 50% or more. If the amount is less than 7145096, the amount of amidoxime after modification is insufficient and a highly functional ultrafine conjugate fiber aggregate that exhibits sufficient effects cannot be obtained. In addition, the amount of grafting was too large, and the apparent density of the fiber aggregate after modification was 0.59/
If it exceeds di, for example, when used underwater, the resistance to flowing water will be too high, and contact with fresh water containing collected ions will be insufficient, resulting in inefficient collection. . Therefore, the grafting reaction must be determined based on the difference in apparent density of the fiber aggregate used.

Amidoximation of the graft fiber can be carried out by a known method using hydroxylamine.

The metal ion-trapping performance of the highly functional ultrafine composite fiber aggregate of the present invention varies depending on the shape of the fiber aggregate in addition to the conditions already mentioned. is 3 to 3 Qmeq per highly functional ultrafine conjugate fiber aggregate 14. 3meq/y
Below, the concentration of amidoxime groups is insufficient and the efficiency is poor;
Moreover, if it exceeds 30 mctq/f, the hydrophilicity of the fiber aggregate becomes too large, resulting in poor morphological stability, and the concentration of amidoxime groups that effectively act on the surface becomes relatively small, resulting in a decrease in efficiency. .

[Example 1] 1. Production of skeletal fiber aggregate by melt-blowing method Polypropylene pellet-like polymer [melt flow rate = 30] was melt-blown with a diameter of 0.5 mm using a melt blowing apparatus described in Jikai Y49-48921, etc. Using 3 m spinning nozzles arranged in a row at 1F1 intervals and having 0.2 mm thick slit gas discharge holes on both sides, the polymer melting temperature was 300°C and the discharge amount per spinning nozzle was 0. 2 y/min, the temperature of the air for blowing jetted out from the slit-shaped gas discharge hole was 300° C., and the heated air pressure for blowing was 2.2 kf/−. At this time, the melt-blown fiber stream was collected by a net-like belt conveyor collector running 20 sub-positions below the spinning nozzle to obtain a fiber aggregate. When this aggregate was observed using a scanning electron microscope, it was found that the fibers were loosely intertwined with each other to form a nonwoven fabric. The basis weight of this melt-prown nonwoven fabric was determined by adjusting the collector speed to the discharge amount per melt-prone device.
d, apparent density was o, 1y/crA. Furthermore, the obtained nonwoven fabric was observed with a scanning electron microscope, and the average fineness of the constituent fibers was determined to be approximately 3 μm. That is, by the method of the present invention, ultra-fine fibers and aggregates using these fibers can be obtained all at once.

2. Production of highly functional ultrafine conjugate fiber aggregate The fiber aggregate obtained in 1.
The sample was irradiated with an electron beam of 20 Mrad(7) at eV and 1 mA, then immersed in acrylonitrile monomer, and a graft reaction was performed at 50° C. for 1 hour under nitrogen. The grafting rate is 300%, which is the same as the grafting rate under the same conditions when using a regular polypropylene fiber nonwoven fabric with a diameter of 25 μm (grafting rate 120% in 1 hour, 150% in 4 hours).
This shows that the effect of the melt-prown nonwoven fabric, which has a larger surface area than that of 13-. Slightly add 3% hydroxycylamine aqueous methanol solution (methanol/water = 5o15
Acrylonitrile Q) amidoximation grafted in 0) was carried out. The amount of amidoxime groups in the obtained highly functional ultrafine conjugate fiber aggregate was 9.5 meq/1 f, and the apparent density was 0.162 P/-.

3. Collection of gold m ions 2. Highly functional ultrafine composite fiber aggregates 0, 1F (
(Its size is about 5 cm x 1 cm), and then put it in 50 tons of seawater and shaken it. One day later, this highly functional ultrafine conjugate fiber aggregate was taken out and 0. After eluting the adsorbed uranyl ions using IN hydrochloric acid and adding the coloring agent arsenazo 2, absorbance was measured to determine the emplacement of the adsorbed uranyl ions. As a result, it was found that uranyl ions of 0.125 W/lg of fiber were collected. This is 0.05η/1 when using a nonwoven fabric with the same amount of amidoxime groups when fabricated using fibers of normal thickness (25 μm).
This shows that the method of the present invention is extremely efficient compared to 14-2 fibers.

[Comparative Example 1] 1. Production of skeleton fiber aggregate by melt-prone method Using the same polypropylene pellet polymer as in Example 1, the discharge amount per spinning nozzle was 0.3 x 7 minutes, and the heating air pressure for the prone was Melt proning was performed under the condition that a 1.8 kf/4 net conveyor was installed 30 cnt below the nozzle to obtain a nonwoven fabric made of fibers with a diameter of about 10 μm. The basis weight of this melt-prone nonwoven fabric is 70r10n”,
The apparent density was 0.08 f/-.

2. Production of highly functional ultrafine conjugate fiber aggregate After irradiating the fiber aggregate obtained in 1 with 20 Mrad radiation, it was brought into contact with acrylonitrile monomer at 40°C for 6 hours to perform a graft polymerization reaction, resulting in a grafting ratio of 300. Obtained excellent fiber. Next, amidoximization was performed using tri-hydroxylamine to introduce a functional group to obtain a highly functional ultrafine conjugate fiber aggregate. The amount of amidoxime groups in this fiber aggregate was 9.0 meq/l P as a result of weight increase measurement, and the apparent density of the fiber aggregate was 0.131 F/-.

3. Collection of metal ions 2. When uranyl ions in seawater were collected in the same manner as in Example 1 using the obtained highly functional ultrafine post-synthetic fiber m aggregate, 0.075η was obtained in one day. /iF fiber uranyl ions were collected. Comparing this result with Example 1,
This indicates that even if the amount of amidoxime groups is approximately the same, when the fibers are thick, the fibers are not sufficiently useful for collecting uranyl ions, probably because the amidoxime groups are present in the fibers.

[Example 2] 6 nylon pellets 50 parts, polypropylene pellets 5
0 parts were melt-mixed and extruded a little using a die to produce seabird fibers with a diameter of 17 μm, each consisting of islands of 6 nylon fiber and polypropylene. When we examined the cross section of this sea-island fiber using a scanning electron microscope, we found that there were about 100 islands with an average diameter of 0.5 μm.
It turned out that it was made from 0 pieces. This fiber was rolled and cut into 51 m lengths to produce a cross-wrapped two-dol punching machine/crA nonwoven fabric. This nonwoven fabric was immersed in a methyl alcohol solution of calcium chloride to elute the nylon sea-island fibers, and washed with methyl alcohol to form a polypropylene laminate fiber.

This nonwoven fabric was irradiated with 20 Mrad, followed by Acryloni I
A grafting reaction of -IJ was carried out to obtain fibers with a grafting rate of 300%. Then, after performing amidoximation, the amount of amidoxime groups in the obtained nonwoven fabric was 12.5 meq/1
f, and the apparent density was 0.16 f/cIA.

Subsequently, uranyl ions in seawater were collected in the same manner as in Example 1, and uranyl ions from o, oc+oq/12 fibers were efficiently collected in one day.

〔Effect of the invention〕

Using the highly functional ultrafine composite fiber aggregate of the present invention, metal ions can be efficiently collected.

7

Claims (2)

[Claims] (1) The fibers are composed of a skeleton fiber with an average diameter of 5 μm or less and a graft portion having an amidoximated functional group that accounts for 50% or more of the weight of the skeleton fiber, and an apparent density of 0.1 to 0.5 g/cm. A highly functional ultrafine composite fiber aggregate that is ^3. (2) Produce a fiber aggregate consisting of skeleton fibers with an average diameter of 5 μm or less, irradiate it with ionizing radiation, and use a monomer that contains a nitrile group and can convert the nitrile group into an amidoxime group to form a fiber aggregate. 1. A method for producing a highly functional ultrafine conjugate fiber aggregate, which comprises graft polymerizing the nitrile group to the fiber of the invention and converting the nitrile group into an amidoxime.