JP4194071B2 - Synthesis method of amidoxime type collector by graft polymerization - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for synthesizing an amidoxime-type collector that efficiently adsorbs and collects useful metals.
[0002]
[Prior art]
Seawater contains rare metals such as vanadium, cobalt, and uranium that are rarely produced in Japan. However, since these exist at a dilute concentration of several milligrams per ton of seawater, there has been no technology that can be collected at an economical price so far.
However, in recent years, research and development has been progressing on collection materials for collecting rare useful metals dissolved in seawater. For example, it has been found that Pb (II) can be adsorbed from river water and seawater by a cation exchange resin using phosphoric acid as an exchange group (see, for example, Non-Patent Document 1).
[0003]
In addition, amidoxime (-C = N (OH) NH ₂ ) groups are selected as functional groups that can selectively adsorb uranium in the ocean, and amidoxime-type collectors introduced into various polymer matrices In the mooring experiment, it is shown that uranium and vanadium can be collected (see, for example, Non-Patent Documents 2 to 4). These techniques involve graft polymerization of acrylonitrile to a nonwoven fabric or fiber (monofilament, filament), or co-graft polymerization of acrylonitrile and methacrylic acid, and then converting the cyano group (—CN) introduced into the graft chain to hydroxylamine. Amidoxime is obtained by reacting with (NH ₂ OH).
[0004]
[Non-Patent Document 1]
Akinori Shiro, 2 others, Cation selectivity and application using phosphoric acid as an exchange group, “PHOSPHORUS LETTER”, Japan Inorganic Phosphorus Society, February 1, 2001, Vol. 40, p. . 16-21
[Non-Patent Document 2]
Akio Katagi, 4 others, Adsorption of amidoxime adsorbent prepared by radiation co-graft polymerization in the sea area, “Journal of the Atomic Energy Society of Japan”, Japan Atomic Energy Society, 1998, Vol. 40, No. 11, p. . 114-116
[0005]
[Non-Patent Document 3]
Akio Katagai, 4 others, Preparation of adsorbents by amidoximation of acrylonitrile and methacrylic acid co-grafted non-woven fabric and actual sea area adsorption experiment, "Journal of the Seawater Society of Japan", Seawater Society of Japan, 1999, Vol. 3, p. 109-113
[Non-Patent Document 4]
Takahiro Hori, 5 others, Synthesis of hollow fiber amide oxime resin for uranium adsorption by radiation graft polymerization, “Journal of the Chemical Society of Japan”, The Chemical Society of Japan, 1986, Vol. 12, p. 1792-1798
[0006]
[Problems to be solved by the invention]
In the conventional amidoxime type collector, acrylonitrile is introduced into the polymer base material by graft polymerization in the production process, but acrylonitrile is a highly toxic substance (lethal amount is 20 ppm, 2 ppm is the allowable limit in Japan). Of course, it is necessary to pay close attention to the safety management of the working environment in the case of large-scale synthesis during industrialization, as well as in batch reactions.
Therefore, there is a need for an amidoxime-type collecting material that does not use acrylonitrile and a method for synthesizing the same in future large-scale utilization of the collecting material.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have succeeded in working by using a compound having a cyano group such as iminopropionitrile instead of acrylonitrile used in the conventional production process. The present invention was completed by discovering that an amidoxime-type collecting material having a high collecting ability can be synthesized while reducing the risk.
That is, the present invention is a method for synthesizing an amidoxime-type collecting material, which includes graft polymerization of a reactive monomer onto a polymer substrate, introducing a cyano group into the graft chain after grafting, and amidoximation of the cyano group. Thus, a method characterized by introducing a cyano group without using acrylonitrile is a means for solving problems.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for synthesizing an amidoxime-type collector, which uses a compound having a cyano group in place of acrylonitrile used in the production process of a conventional amidoxime-type collector.
Specifically, the present invention relates to an amidoxime-type collector comprising graft polymerization of a reactive monomer onto a polymer substrate, introducing a cyano group into the graft chain after grafting, and amidoximation of the cyano group. A synthesis method, which is characterized in that a cyano group is introduced without using acrylonitrile.
[0009]
The synthesis method of the present invention comprises (1) a reactive site generation reaction in which a reactive site is generated in advance on a polymer substrate; (2) a graft polymerization reaction in which a reactive monomer is graft-polymerized on the polymer substrate; and (3 3) A chelate-forming group introduction reaction in which a cyano group is introduced into a graft chain to form amidoxime.
[0010]
(1) Reaction active point generation reaction In the present invention, the polymer base material may be polyethylene, polypropylene, or the like, and the form may be a nonwoven fabric or fiber (single fiber, filament).
In order to graft polymerize a reactive monomer on such a polymer substrate, a reactive site is generated in advance by any of the following methods (a) to (c).
[0011]
(A) Irradiation A polymer substrate previously substituted with nitrogen is irradiated with radiation under a nitrogen atmosphere, at room temperature or under cooling with dry ice. The radiation to be used is an electron beam or γ-ray, and the irradiation dose can be appropriately determined on the condition that it is a dose sufficient to generate a reactive site, but it is typically 50 to 200 kGy.
(B) Plasma irradiation Plasma is irradiated to a polymer base material previously substituted with nitrogen at room temperature in a nitrogen atmosphere. The substrate is irradiated for 1 to several hours using a high frequency of 10 MHz or more in a nitrogen atmosphere.
(C) Use of initiator A reactive site is generated using a radical initiator in the range of room temperature to 50 ° C under nitrogen bubbling. As the radical initiator, for example, azobisisobutyronitrile or benzoyl peroxide can be used.
[0012]
(2) Graft polymerization reaction In the method of the present invention, after a reactive site is formed on a polymer substrate, a reactive monomer is brought into contact with the polymer to perform graft polymerization. Is introduced.
The reactive monomer that can be used in the present invention is a vinyl reactive monomer having a glycidyl group. Such monomers are specifically selected from the group consisting of glycidyl methacrylate, glycidyl acrylate, glycidyl methyl styrene or mixtures thereof. By forming a graft chain using these reactive monomers and introducing a cyano group in the subsequent chelate group forming reaction, it becomes possible to form an amidoxime group without using acetonitrile.
[0013]
Graft polymerization can be performed in a nitrogen atmosphere, but in order to achieve a high graft ratio, it is preferable that the oxygen concentration in the atmosphere is low. Here, “graft ratio” refers to the weight ratio (%) of reactive monomers graphed on a polymer substrate. The reaction temperature depends on the reactivity of the reactive monomer, but is typically 40 to 60 ° C, preferably 40 ° C. The reaction time is 30 minutes to 5 hours, but can be determined depending on the reaction temperature and the required grafting rate. The monomer concentration in the reaction solvent is usually about 10%, but it becomes a factor for determining the reaction rate together with the reaction temperature and reaction time, and can be appropriately determined according to the required reaction rate.
[0014]
(3) Chelate-forming group introduction reaction In the method of the present invention, the glycidyl methacrylate-polymerized graft chain is then reacted with a compound having a cyano group to introduce a cyano group, which is converted into an amidoxime to form a chelate. Group (amidoxime group). A chelate-forming group, that is, an amidoxime group forms a chelate with a useful metal dissolved in seawater, and thereby exhibits an effect as a trapping material.
[0015]
As the compound having a cyano group, for example, iminopropionitrile can be used. The reaction time can be determined depending on the iminopropionitrile density obtained by the reaction. The dependence of iminopropionitrile density on the reaction time is shown in FIG.
The cyano group introduced into the graft chain by iminopropionitrile formation can be converted into an amidoxime group by reacting with hydroxylamine. The reaction time of amidoximation can be determined depending on the amidoxime group density obtained by the reaction. The dependence of the amidoxime group density on the reaction time is shown in FIG.
EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited by these Examples.
[0016]
【Example】
Example 1 Synthesis of Collection Material Using Nonwoven Fabric as Polymer Base Material A nonwoven fabric was used as the polymer base material, and this was irradiated with radiation to generate reaction active sites. Irradiation was performed at a dose of 200 kGy in a nitrogen atmosphere. Next, glycidyl methacrylate is reacted at a concentration of 10 to 30% in methanol, dimethyl sulfoxide, or a mixed solvent thereof of 1: 1 (weight ratio) for 30 minutes to 2 hours at 40 ° C. to introduce graft chains into the nonwoven fabric. did.
This graft product was reacted with iminopropionitrile at 80 ° C. for 12 to 80 hours, followed by reaction for 1 to 2 hours in a 3 to 6% hydroxylamine hydrochloride mixed solution (water / methanol = 1/1).
[0017]
The resulting nonwoven fabric collecting material had an amidoxime group density of 2 to 4 mmol / g. This collection material is a collection material having a conventional hydrophilic group (when 10 mg of collection material is brought into contact with 1 L of seawater and a collection test is performed for 30 minutes, 5 mg of uranium is collected per 1 kg of collection material. Or 2 g of uranium can be recovered per 1 kg of the collected material when the collected material is immersed in the actual sea for one month). It was also found that the speed of vanadium adsorption was three times faster.
[0018]
Example 2 Synthesis of trapping material using a single fiber as a polymer base material A single fiber was used as a polymer base material, and a reactive site was generated by irradiating it with radiation. Irradiation was performed using an electron beam or γ-ray in a nitrogen atmosphere so that the total dose was 200 kGy.
Next, glycidyl methacrylate was reacted at 40% in methanol, dimethyl sulfoxide, or a 1: 1 (weight ratio) mixed solvent thereof at a concentration of 10% for 1 hour to introduce graft chains into the nonwoven fabric.
This graft product was reacted with iminopropionitrile at 80 ° C. for 12 hours, and subsequently reacted in a 3 to 6% hydroxylamine hydrochloride mixed solution (water / methanol = 1/1) for 1 to 2 hours.
The obtained single fiber collecting material had an amidoxime group density of 2 to 4 mmol / g. This trapping material had almost the same performance as conventional trapping materials having hydrophilic groups (shown in Example 1).
【The invention's effect】
According to the synthesis method of the present invention, the working environment at the time of producing an amidoxime-type collector by radical polymerization (particularly graft polymerization) is improved, and mass synthesis is facilitated. Moreover, there exists an advantage that the environmental measure at the time of graft polymerization reaction is eased regarding synthesis.
[Brief description of the drawings]
FIG. 1 is a graph showing the reaction time dependence of iminopropionitrile density.
FIG. 2 is a graph showing the reaction time dependence of amidoxime group density.

Claims (2)

A reactive monomer, which is a vinyl reactive monomer having a glycidyl group, is graft-polymerized on a polymer substrate existing in the form of a nonwoven fabric or fiber, and after grafting, a cyano group is introduced by reacting iminopropionitrile with the graft chain. And a method for synthesizing an amidoxime-type trapping material, wherein the cyano group is amidoxime-ized. Reactive monomer is glycidyl methacrylate, glycidyl acrylate is selected from the group consisting of glycidyl methyl styrene or mixtures thereof, The method of claim 1.

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