JP4465447B2 - Method for synthesizing phosphate-based collectors by graft polymerization - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for synthesizing a phosphate-based collection material 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 they exist at a dilute concentration of several milligrams per ton of seawater, it has been extremely difficult to collect them at an economical price.
In recent years, research and development have been advanced on a collection material 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 are collected (see, for example, Non-Patent Documents 2 to 5). These techniques include (1) graft polymerization of acrylonitrile onto a nonwoven fabric or fiber (single fiber, filament), or co-graft polymerization of acrylonitrile and methacrylic acid, and then (2) a cyano group introduced into the graft chain ( amidoxime by causing a -CN) is reacted with hydroxylamine (NH ₂ OH), it is made of a two step process.
[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]
Tomomi Kawai, 7 others, Preparation of hydrophilic amidoxime fibers by cografting acrylonitrile and methacrylic acid from an optimized monomer composition) “Radiation Physics and Chemistry” (UK), Elsevier Science Ltd. 2000, Vol. 59, p. 405-411
[0005]
[Non-Patent Document 3]
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
[Non-Patent Document 4]
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 5]
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]
A conventional method for producing an amidoxime-type trapping material includes (1) a graft polymerization step for introducing a reactive monomer into a polymer substrate, and (2) a metal trapping group introduction step for introducing a metal trapping group into the graft chain. The two-stage process was required.
Therefore, in future large-scale utilization of the trapping material, there is a need for mass synthesis by a simple method consisting of fewer steps.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have selected a monomer having a mono- or bifunctional phosphate group as a reactive monomer, thereby making it easier than conventional phosphors. The present invention relating to a method for producing an acid-based collecting material has been completed.
That is, the present invention is a method for synthesizing a phosphoric acid group-type trapping material comprising graft polymerization of a reactive monomer having a monofunctional or bifunctional phosphoric acid group on a polymer substrate, The problem solving means is a method characterized in that the introduction is performed in a one-step process.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for synthesizing a phosphoric acid group-type trapping material comprising graft polymerization of a reactive monomer having a mono- or bifunctional phosphoric acid group onto a polymer substrate, and introducing the phosphoric acid group Is an invention relating to a method characterized in that is performed in a one-step process. Here, the “one-step process” means that the introduction of a phosphate group is not performed in a plurality of processes in which a reactive monomer is graft-polymerized on a polymer substrate and then chemically treated. It is carried out in a one-step process in which the monomer having it is graft-polymerized and directly introduced into the polymer substrate.
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).
[0009]
As the reactive monomer to be introduced into such a polymer substrate, a monomer having a monofunctional or bifunctional phosphate group can be used. Specifically,
Mono (2-methacryloyloxyethyl) acid phosphate _{CH 2 = C (CH 3)} COO (CH 2) 2 OPO (OH) 2;
Di (2-methacryloyloxyethyl) acid phosphate [CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₂ O] ₂ PO (OH);
Mono (2-acryloyloxyethyl) acid phosphate _{CH 2 = CHCOO (CH 2)} 2 OPO (OH) 2;
Di (2-acryloyloxyethyl) acid phosphate [CH ₂ ═CHCOO (CH ₂ ) ₂ O] ₂ PO (OH);
Or these mixed monomers can be used.
When using mixed monomers, the mixing ratio of each monomer can be changed as appropriate.
[0010]
In addition, types having the following structures can also be used as reactive monomers.
_{CH 2 = C (CH 3)} COO (CH 2) l OCO-R-CO-OPO (OH) R '
(In the formula, R is optionally substituted (CH ₂ ) _m or C ₆ H ₄ , and R ′ is a hydroxyl group or CH ₂ ═C (CH ₃ ) COO (CH ₂ ) _n OCO—R— CO—O— group, and l, m and n are each independently an integer of 1 to 6.)
In the method of the present invention, the graft polymerization can be carried out by bringing a reactive monomer into contact with the polymer substrate after generating a reactive site.
The reaction active site can be generated by any of the following methods (a) to (c).
[0011]
(A) Irradiation A polymer substrate previously substituted with nitrogen is irradiated with radiation in 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 24 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]
Graft polymerization can be performed in a nitrogen atmosphere, but in order to achieve a higher graft ratio, it is preferable that the oxygen concentration in the atmosphere is low. Here, the “grafting ratio” refers to the weight ratio (%) of the reactive monomer grafted on the polymer substrate. The reaction temperature depends on the reactivity of the reactive monomer, but is generally 40 to 60 ° C. The monomer concentration may be 10 to 30% with respect to the solvent. The reaction time is generally from 1 to 48 hours, but can be determined depending on the reaction temperature and the required graft rate. FIG. 1 shows the reaction time dependence of the grafting rate of the phosphoric acid type collector according to the present invention.
EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited by these Examples.
[0013]
【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 using an electron beam under conditions of a total dose of 200 kGy in a nitrogen atmosphere.
[0014]
Next, a monomer mixture of mono (2-methacryloyloxyethyl) acid phosphate and di (2-methacryloyloxyethyl) acid phosphate (mono / di = 70/30%) as a monomer having a phosphoric acid group in a concentration of 10 to 30% Then, the mixture was reacted in a mixed solvent of methanol and pure water (methanol 10 to 30% by weight) for 3 to 24 hours at 40 to 60 ° C. to introduce graft chains into the nonwoven fabric. The reaction rates were 90% and 200% when reacted at 60 ° C. for 2 hours and 12 hours, respectively.
In this way, when metal ions (lead, cadmium, chromium, etc.) are passed through the graft product into which phosphate groups have been introduced, metal ions can be collected up to 90% of the theoretical adsorption amount. It was shown that the material has a high adsorption capacity.
[0015]
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 under conditions of a total dose of 200 kGy in a nitrogen atmosphere.
Next, as a monomer having a phosphate group, a mixed monomer of mono (2-methacryloyloxyethyl) acid phosphate and di (2-methacryloyloxyethyl) acid phosphate (mono / di = 70/30%) at a concentration of 10%, The reaction was carried out in a mixed solvent of methanol and pure water (methanol 10 to 30% by weight) for 12 hours at 50 ° C. to introduce graft chains into single fibers. The reaction rates were 120% and 250% when reacted for 2 hours and 12 hours, respectively.
In this way, when metal ions were passed through the graft product into which phosphate groups were introduced, in the case of lead, almost 100% could be removed in 12 hours. The adsorption performance with respect to lead of the phosphoric acid type collecting material of the present invention is shown in FIG.
【The invention's effect】
According to the synthesis method of the present invention, it is possible to produce a collecting material by a one-step reaction including only a graft polymerization reaction, and there is an advantage that mass production on a commercial scale in the future becomes easy.
[Brief description of the drawings]
FIG. 1 is a graph showing the reaction time dependence of the grafting rate of a phosphoric acid type trapping material.
FIG. 2 is a diagram showing the adsorption performance of a phosphoric acid type collecting material with respect to lead.

Claims (1)

  Synthesis of phosphate group-type trapping material comprising simultaneously graft-polymerizing two monomers having monoester and diester structures among reactive monomers having mono- or bifunctional phosphate groups onto a polymer substrate The process wherein the reactive monomer is mono (2-methacryloyloxyethyl) acid phosphate, di (2-methacryloyloxyethyl) acid phosphate, mono (2-acryloyloxyethyl) acid phosphate, or di (2-acryloyl). A method for synthesizing a phosphate-based collector, characterized in that it is (oxyethyl) acid phosphate.

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