JP4960719B2 - Anion exchange net - Google Patents

Description

The present invention relates to an anion exchange net disposed between an anion exchange membrane and a cation exchange membrane during electrodialysis .

  Electrodialysis desalination of electrolyte solution was first developed in the 1950s for the purpose of desalination of brackish water, followed by concentration of seawater for the production of salt, soy sauce and whey desalination, and various chemicals. It has been used for various purposes such as process rationalization, wastewater treatment, and separation of impurities in wine.

  The electrodialyzer has an anode chamber and a cathode chamber at both ends, and an anion exchange membrane and a cation exchange membrane are alternately disposed between the anode chamber and the cathode chamber, and a desalting chamber and a concentration chamber are alternately formed. In such an electrodialysis apparatus, the ion exchanger, which is an ion conductor, is accommodated in the desalting chamber, so that the electrical conductivity is improved and is mainly caused by a potential difference at the interface (contact point) with the exchanger of different ions. It is known that the “hydrolysis” phenomenon is less likely to occur, and the electrolyte can be desalted in a low concentration range.

  As an ion exchanger used in such an electrodialysis apparatus, a nonwoven fabric made of a fibrous ion exchanger is known. As such a nonwoven fabric, for example, a polyolefin or a fluorinated polyolefin is used, and a nonwoven fabric made of porous fibers is formed by a stretch opening method, and the pores are filled with a styrene / divinylbenzene-based ion exchange polymer. (See Patent Document 1), and a non-woven fabric made of polyolefin or fluorinated polyolefin fiber, which is obtained by introducing an ion exchange group after performing graft polymerization with radiation (see Patent Document 2), etc. have been proposed. However, when these fibrous ion exchangers are used for electrodialysis, the solution not only passes through a narrow fiber gap, but also passes through a long distance in the width or length direction of the nonwoven fabric, so there is a problem that the pressure loss is large. is there.

  Therefore, it has been proposed to dispose an ion exchange net between a cation exchange membrane and an anion exchange membrane in place of the nonwoven fabric made of the fibrous ion exchanger as described above. In the first place, in an electrodialysis apparatus, a net called a spacer is interposed between a cation exchange membrane and an anion exchange membrane. The role of the spacer includes intervening between the membranes to prevent contact between the membranes, and a partition between the desalting chamber and the concentration chamber, mechanical support of the membrane, and stirring and mixing of the desalted solution. By adding an ion exchange group to this spacer to form an ion exchange net, the limit current density can be improved, and as a result, the required membrane area can be reduced and desalting can be performed in a low electrolyte concentration region. Become. Furthermore, it becomes possible to prevent the desalination performance from being lowered by the ion exchange resin and the pressure loss in the fibrous ion exchanger.

  Thus, by using an ion exchange net as a spacer, when performing desalting in an electrodialyzer, in addition to an ion exchange membrane that becomes a water passage, the spacer also captures ions, so the ion concentration of water is Even if it decreases, ions can move efficiently at a low voltage. Therefore, for example, when taking out water from seawater, pure water with high purity can be taken out.

  As a method for producing an ion exchange net, a method in which a pulverized ion exchange resin is mixed with an aqueous solution of a hydrophilic polymer, this solution is applied to a polymer material of a commercially available net, and dried to crosslink the hydrophilic polymer (Patent Literature). However, it has not been put into practical use because of the low exchange capacity of the obtained ion exchange net.

In addition, the applicant first formed an anion exchange precursor net by molding an ethylene-glycidyl methacrylate copolymer into a net, and then converted the functional group (glycidyl group) in the net into an anion exchange group. Proposed a method for producing an anion exchange net (Japanese Patent Application No. 2005-223340). According to this method, an anion exchange net having a relatively high exchange capacity can be produced.
JP2002-95978 JP 4-293811 US Pat. No. 6,090,258

  However, the conventionally known anion exchange nets are not only high in ion exchange capacity but also poor in flexibility. For example, electrodialysis is performed by placing them between an anion exchange membrane and a cation exchange membrane as a spacer. In this case, there is a problem that a sufficient contact area cannot be ensured between the net and the ion exchange membrane, and liquid leakage is likely to occur, and further improvement in characteristics is required.

Accordingly, an object of the present invention is to provide an anion exchange net used for an electrodialysis apparatus, which has a high ion exchange capacity and a high flexibility.

  As a result of intensive studies on the anion exchange resin that forms the anion exchange net, the present inventors have used a thermoplastic resin having a functional group capable of introducing an anion exchange group. When an anion exchange resin is produced by reacting a polyamino compound to fix an amino group on the thermoplastic resin and then quaternizing the amino group, a thermoplastic resin having a low softening point is used. As a result, the inventors have found a novel finding that an anion exchange resin having a high anion exchange capacity and an excellent flexibility when used as an anion exchange net can be obtained, thereby completing the present invention.

That is, according to the present invention, in an anion exchange net comprising an anion exchange resin formed in a net shape,
The anion exchange resin has a structural unit having at least one functional group selected from the group consisting of a glycidyl group, an epoxy group, and an acid anhydride group and a vinyl acetate structural unit, and the vinyl acetate structural unit Obtained by introducing anion exchange groups into the thermoplastic copolymer contained at a rate of 0.3 to 2.0 mmol / g, an anion exchange capacity of 1.5 mmol / g or more and a water content of 25% or more An anion exchange net characterized by having:

The anion exchange net of the present invention is
(1) In addition to the vinyl acetate structural unit, the copolymer has an ethylene structural unit and a glycidyl methacrylate structural unit.
(2) From the anion exchange capacity and water content , the fixed ion concentration determined by the following formula is in the range of 6 to 10 mmol / g,
Fixed ion concentration = (anion exchange capacity / water content) × 100
Is preferred.

In the present invention, the anion exchange resin formed in a net shape is
A structural unit having at least one functional group selected from the group consisting of a glycidyl group, an epoxy group, and an acid anhydride group, and a vinyl acetate structural unit; Preparing a thermoplastic copolymer containing at a rate of 0.0 mmol / g and having a Vicat softening point of 70 ° C. or lower;
A step of reacting the thermoplastic copolymer with a polyamino compound having a plurality of amino groups and having a molecular weight in the range of 100 to 10,000, and fixing the polyamino compound in the thermoplastic copolymer;
A step of reacting an alkyl halide with the thermoplastic copolymer to which a polyamino compound is fixed to quaternize an amino group;
Manufactured by a process consisting of

In the above anion exchange resin production process,
(1) The thermoplastic copolymer has an ethylene structural unit and a glycidyl methacrylate structural unit in addition to the vinyl acetate structural unit,
Is preferred, but
(2) The thermoplastic copolymer has a high softening point resin component having the functional group and a Vicat softening point higher than 80 ° C, and a low softening point resin component having a Vicat softening point of 80 ° C or lower. A blend of
(4) The high softening point resin component is an ethylene-glycidyl methacrylate copolymer, and the low softening point resin component is polyvinyl acetate.
It is also possible to adopt such a mode.

That is, the anion exchange net of the present invention can be obtained by molding the anion exchange resin produced as described above into a net shape.

The anion exchange resin forming the anion exchange net of the present invention is characterized by an anion exchange capacity of not less than 1.5 mmol / g and a very high water content of 25% or more. is there. That is, when electrodialysis is performed using an anion exchange net formed using such an anion exchange resin having a high anion exchange capacity, the electrical resistance between the ion exchange membranes can be reduced. In addition, this anion exchange resin exhibits high swellability when an anion exchange net formed from this anion exchange resin is immersed in an electrolyte solution in relation to having a high water content. When electrodialysis is performed between ion exchange membranes, a sufficient contact area can be ensured between the net and the ion exchange membrane, and liquid leakage can be reliably prevented. The electrical resistance can be reduced. As described above, the anion exchange resin of the present invention is extremely useful as an anion exchange net used for electrodialysis. By using an anion exchange net formed from such an anion exchange resin, electrodialysis can be efficiently performed with low conductivity. It can be performed.

  Further, as will be described later, the amount of anion exchange groups introduced can be easily controlled by changing the reaction conditions with the polyamino compound. In order to improve electrochemical performance, it is preferable to introduce an exchange group into the anion exchange resin (or an anion exchange net obtained by molding the resin into a net shape). Further, it is not preferable because it causes a decrease in dimensional stability. Therefore, it is preferable to easily control the reaction conditions according to the usage form of the anion exchange resin, and the merit of easily controlling the amount of exchange group introduced is great.

  Further, the one using the radiation graft polymerization proposed in Patent Document 2 is a radical reaction, and there is a concern about the oxidation degradation of the resin. is there.

In the present invention, the water content is, as shown in Examples described later, an anion exchange resin (or an anion exchange net obtained by molding the resin into a net shape) immersed in seawater, The wet weight is measured, and then dried under predetermined conditions (see Examples for the drying conditions), and can be obtained from the following formula.
Moisture content (%) = (WD) × 100 / D
W: Wet weight
D: Dry weight

In addition, the above-mentioned anion exchange resin is rich in flexibility and exhibits high swellability because of its high moisture content. However, such a large moisture content is due to the presence of anion exchange groups up to the inside of the resin. This is probably because it has been introduced. For example, it is known that the water content increases as the amount of anion exchange groups introduced into the resin increases. In this case, the introduced anion exchange group present on the surface of the resin contributes the most to the improvement of the moisture content, but the anion exchange group introduced into the resin is not as much as the anion exchange group introduced into the surface. Anyway, it contributes to the improvement of the moisture content. That is, the high water content of the anion exchange resin of the present invention means that the anion exchange group is effectively introduced not only on the resin surface but also inside the resin.

Furthermore, since the anion exchange resin molded into a net shape has an anion exchange resin introduced not only to the surface of the resin but also to the inside of the resin, it is understood from the experimental results (Table 1) of Experimental Example 1 described later. As shown, the fixed ion concentration (anion exchange capacity / water content) determined from the anion exchange capacity and water content is in the range of 6 to 10 mmol / g.
For example, when most of the anion exchange groups are introduced on the resin surface and not so much inside the resin, the anion exchange groups on the resin surface greatly contribute to the water content, so this value is in the above range. It becomes a smaller value. On the other hand, the anion exchange resin used in the present invention has a large number of anion exchange groups inside as well as the surface anion exchange groups that greatly contribute to the water content. This is considered to indicate a large value. That is, the anion exchange resin used in the present invention is considered to have a structure in which a large number of anion exchange groups are introduced in the interior due to an increase in the fixed ion concentration.

Thus, in the present invention, the anion exchange resin formed into a net shape has a high anion exchange capacity because the anion exchange group is effectively introduced to the inside, and increases the energization resistance during electrodialysis. In addition to being effective in avoiding, an anion exchange group that contributes to improving the water content up to the inside of the resin has been introduced, so when it is immersed in an electrolyte solution, it exhibits a significantly high swellability. For example, an increased contact area with the ion exchange membrane can be ensured, and in combination with a high anion and high capacity, electrodialysis can be performed efficiently.

Further, as will be understood from the examples described later, the anion exchange resin having the above-described characteristics uses a thermoplastic copolymer having a Vicat softening point of 70 ° C. or less, and an anion exchange group is introduced into the thermoplastic copolymer. When an anion exchange group is introduced into a thermoplastic copolymer having a Vicat softening point larger than the above range , an anion exchange resin having the above properties cannot be obtained.

<Manufacture of anion exchange resin>
As the anion exchange resin used in the present invention, a thermoplastic copolymer having a functional group capable of introducing an anion exchange group (hereinafter simply referred to as a thermoplastic resin) is used, and an amino group is introduced into the resin. It is produced by quaternizing the amino group fixed therein.

-Raw material thermoplastic resin-
In the present invention, the thermoplastic resin used as a starting material contains a functional group capable of introducing an anion exchange group, specifically, at least one selected from the group consisting of a glycidyl group, an epoxy group and an acid anhydride group. It is a waste. In other words, these functional groups are reactive with amino groups having anion exchange ability, and amino groups having anion exchange ability are introduced into the thermoplastic resin using these functional groups. The Rukoto.

  Therefore, it is necessary that the raw material thermoplastic resin contains the functional group in an amount corresponding to the anion exchange capacity of the finally obtained anion exchange resin, and generally 0.1 to 10 mmol. It preferably has a functional group concentration of / g. If the functional group concentration is 0.1 mmol / g or less, a sufficient anion exchange capacity cannot be obtained, and if it is 10 mmol / g or more, it becomes extremely difficult to form a net.

  In the present invention, it is important that the thermoplastic resin has a Vicat softening point of 70 ° C. or lower. That is, when a thermoplastic resin having a Vicat softening point higher than 70 ° C. is used, a high anion exchange capacity and water content cannot be obtained, as is apparent from the experimental results of Examples described later. The reason why a high anion exchange capacity and water content can be obtained by using such a low softening point thermoplastic resin has not been clearly elucidated. When the group is converted to an amino group, the thermoplastic resin is in a softened state having a moderate fluidity, and as a result, the polyamino compound is effectively brought into contact with the inside of the thermoplastic resin, resulting in the thermoplasticity. It seems that many anion exchange groups are also introduced inside the resin.

Further, in terms of increasing the anion exchange capacity and water content, the lower the Vicat softening point is better, but on the other hand, the strength of the resulting anion exchange resin is reduced. Therefore, the Vicat softening point of the thermoplastic resin used is from the viewpoint of avoiding strength reduction,
It is suitable that it is 30 ° C. or higher.

In the present invention, the above-mentioned thermoplastic resin having a functional group may be an olefin resin or an acrylic resin modified with the functional group (glycidyl group, epoxy group, maleic anhydride group), such as ethylene-glycidyl (meta ) Acrylate copolymers, maleic anhydride modified (meth) acrylates, maleic anhydride modified polyolefins, etc. Especially for these polymers, the Vicat softening point can be increased by copolymerizing vinyl acetate (or polyvinyl acetate). The range can be adjusted. That is, in the present invention, the one in which vinyl acetate or polyvinyl acetate is introduced and the softening point is adjusted to the above range is used. In particular, in the present invention, from the viewpoint of easy adjustment of the softening point without impairing the moldability, an ethylene-glycidyl methacrylate copolymer is used, and the softening point is copolymerized with vinyl acetate. It is most preferable to use a material adjusted to the range as a raw material thermoplastic resin.

For example, an ethylene-glycidyl methacrylate copolymer having a glycidyl group concentration in the above-mentioned range is generally a high softening point component having a Vicat softening point higher than 80 ° C., and an appropriate glycidyl group In order to maintain the concentration, the Vicat softening point can be adjusted to the above range by copolymerizing vinyl acetate or polyvinyl acetate in an amount of vinyl acetate structural unit of 0.3 to 2.0 mmol / g. Such an ethylene-glycidyl methacrylate-vinyl acetate copolymer can be used as a raw material thermoplastic resin .

  Moreover, since the ethylene-glycidyl methacrylate-vinyl acetate copolymer into which polyvinyl acetate or vinyl acetate unit is introduced is a low softening point component having a Vicat softening point of 80 ° C. or less, such a low softening point component is By blending with the above-described thermoplastic resin component having a high softening point, the Vicat softening point can be adjusted to the above-described range and used as a raw material thermoplastic resin composition. Of course, even in such a blend, the functional group amount should be set within the above-mentioned range.

  The raw material thermoplastic resin used in the present invention is not particularly limited as long as it contains a predetermined amount of functional groups and has a predetermined Vicat softening point. In consideration of ease of molding, those having a melt flow rate (MFR, 230 ° C.) in the range of 0.1 to 250 g / 10 min are preferable. In addition, as long as an anion exchange group is introduced to the inside of the resin and a high anion exchange capacity and moisture content are obtained, high melting point polymers such as various inorganic fillers and liquid crystalline polyesters are blended for improving moldability and reinforcement. Also good.

-Introduction of amino group-
In the present invention, the raw material thermoplastic resin is reacted with a polyamino compound, an amino group is introduced into the resin, and the amino group is quaternary ammonium chloride. Prior to the introduction of such an amino group, The thermoplastic resin is preferably molded into a net shape. That is, if molding is performed after the introduction of amino groups, there is a risk of performance degradation due to thermal history.

  Such net-shaped molding is not particularly limited, such as knitting or weaving of thermoplastic resin yarns (strands), but is preferably performed by integral extrusion molding of the thermoplastic resin.

  Such integral extrusion can be performed by a known method described in, for example, Japanese Patent Publication No. 34-4185 and Japanese Patent Laid-Open No. 53-49170. As an example, as shown in FIG. 1, for example, as shown in FIG. 1, a die mold provided at the tip of the extruder includes an outer mold 1 that can rotate relatively and a core mold 2 provided inside the outer mold. Use a structure. A plurality of grooves 1a serving as resin flow paths are formed on the inner surface of the outer mold 1 at appropriate intervals. On the other hand, a plurality of grooves 2a serving as resin flow paths are formed on the outer surface of the core mold 2 at appropriate intervals. Has been. Therefore, while the outer mold 1 and the core mold 2 are relatively rotated (usually rotating in opposite directions to each other), the resin is melt-extruded to form a cylindrical ion formed into a net shape. An exchange precursor net can be obtained. That is, the portion that is pushed out when the groove 1a and the groove 2a are matched becomes the bridging portion of the net. According to such a method, the size of the opening of the net can be easily adjusted by adjusting the rotational speed of the outer mold and the core mold.

  The ion exchange precursor net extruded into a cylindrical shape as described above is cooled and solidified to stabilize the shape, and then taken up and cut. The cooling and solidification is performed, for example, by introducing it into water immediately after extrusion. At this time, it is preferable to place a cylindrical mandrel (sizing) in the water and perform extrusion so as to wrap the mandrel. That is, the inner diameter of the cylindrical ion exchange precursor net can be adjusted according to the outer diameter of the mandrel by performing cooling and solidification while pressing the molten cylindrical ion exchange precursor on the mandrel. For example, if the inner diameter is adjusted so that the circumference of this cylindrical ion exchange net corresponds to the spacer width when used as a spacer of an electrodialyzer, without post-processing such as shape adjustment, The ion exchange net can be used as a spacer as it is. The take-off / cutting after cooling and solidification is performed by a method known per se, whereby a sheet-like ion exchange precursor net is obtained.

  In the present invention, amino groups are introduced into the sheet-shaped ion exchange precursor net formed as described above. The amino group is introduced by reacting a polyamino compound having a plurality of amino groups with the functional group present in the thermoplastic resin constituting the net.

  The polyamino compound has a plurality of primary amino groups or secondary amino groups from the viewpoint of reactivity with the functional group (that is, glycidyl group, epoxy group or acid anhydride group). In addition, the molecular weight of such a polyamino compound needs to be in the range of 100 to 10,000. That is, in the present invention, since a raw material thermoplastic resin having a low softening point is used, if a polyamino compound having a molecular weight smaller than the above range is used, a problem of strength reduction is caused, and the molecular weight is If a polyamino compound larger than the range is used, it becomes difficult to react the polyamino compound to the inside of the net (thermoplastic resin), and it becomes difficult to obtain the desired high anion exchange capacity and moisture content. Because it ends up. Therefore, in the present invention, as the polyamino compound, polyallylamine, polyethyleneimine or the like having a molecular weight within the above range is preferably used.

  The reaction between the net made of the thermoplastic resin and the amino compound is carried out by immersing the net in the liquid of the amino compound. The liquid of the amino compound to be used is, if necessary, the amino group and the thermoplastic resin in the thermoplastic resin. It can be diluted with an organic solvent that does not react with the functional group and is incompatible with the thermoplastic resin. However, the concentration of the amino compound in such a diluted solution is preferably 1% by weight or more. This is because if the concentration is too low, the reaction efficiency between the amino group and the functional group decreases, and the reaction takes a long time.

  The reaction between the thermoplastic resin (ion exchange precursor net) and the amino compound is generally carried out by heating in the range of 10 to 130 ° C., although it varies depending on the type of functional group of the thermoplastic resin. When the reaction temperature is lower than the above range, the progress of the reaction becomes rate-determined, and it takes a long time to distribute a sufficient amount of amino compound in the net to obtain a sufficient exchange capacity, resulting in a decrease in productivity. This is because if the temperature is higher than the above range, the net may be melted and deformed. If the reaction is in the range of 10 to 130 ° C., the amount of exchange groups introduced can be easily controlled. That is, when giving priority to the introduction amount of exchange groups over mechanical strength, the reaction is performed at a relatively high temperature in the above temperature range, and when giving priority to mechanical strength over exchange amount introduction, it is compared. It is preferable to carry out the reaction at a low temperature. Such a reaction is usually performed for about 1 to 50 hours. In the reaction time, as with the reaction temperature, the amount of exchange group introduced can be increased by increasing the reaction time.

  In the present invention, since the raw material thermoplastic resin having the aforementioned low softening point is used, the net formed from the resin by the above reaction has moderate fluidity, so that the polyamino compound It is considered that the amino group penetrates into the inside of the net and an amino group is introduced, and a high exchange capacity and water content can be obtained.

  In the present invention, the amino compound (amino group) is fixed to the thermoplastic resin forming the net by the above reaction.

  After fixing the amino compound in this way, quaternary ammonium chloride is carried out by using a quaternary ammonium agent and converting the amino group to a quaternary ammonium group. As such a quaternary ammonium agent, monohalogenated alkyls such as methyl fluoride, methyl chloride, methyl bromide, methyl iodide and the like are preferably used. Methyl is used.

  The above quaternization reaction is facilitated by using a solution in which a quaternary ammonium agent is dissolved in an appropriate organic solvent, and immersing the ion exchange precursor net in which the amino compound is fixed in the solution. To be done. In this case, in the quaternization reaction with methyl iodide, since the boiling point of methyl iodide is as low as 43 ° C., it is desirable that the quaternization is performed at a temperature equal to or lower than the boiling point temperature for about one day.

  After the quaternary ammonium conversion is performed as described above, washing is performed using an aqueous sodium sulfite solution to remove free iodine and the like, and the anion exchange network made of the anion exchange resin of the present invention is used. Is obtained.

<Anion exchange resin>
The anion exchange resin thus obtained has a large anion exchange capacity and a high water content because many anion exchange groups are introduced not only to the surface but also to the inside. Specifically, the anion exchange capacity is 1 It is in the range of 0.5 mmol / g or more, and the water content is as extremely high as 25% or more. Furthermore, since the anion exchange group is introduced to the inside, the fixed ion concentration is in the range of 6 to 10 mmol / g. In the case where anion exchange groups are not effectively introduced to the inside and a large amount of anion exchange groups are distributed on the surface, the fixed ion concentration is higher than the above range even if high anion exchange capacity and water content are exhibited. Low.

The anion exchange net of the present invention obtained by molding the above anion exchange resin into a net shape is extremely useful as an anion exchange net used for electrodialysis, and is particularly arranged as a spacer between the anion exchange membrane and the cation exchange membrane. By doing so, electrodialysis can be performed efficiently with low conductivity. In particular, an anion exchange net used as a spacer is not particularly limited in the setting of the opening area ratio and thickness per unit area, but the opening area ratio per unit area is set to about 30 to 70%, and the thickness is It is preferable that the thickness is set to about 0.3 to 2.0 mm.

Hereinafter, the present invention will be described in more detail with reference to experimental examples.
The physical properties of the thermoplastic resin used in the following experimental examples are as follows.

(Raw material thermoplastic resin)
Resin A:
Ethylene-glycidyl methacrylate-vinyl acetate copolymer Glycidyl group content: 0.93 mmol / g
Vinyl acetate content: 0.58 mmol / g
Vicat softening point: 68 ° C
Resin B:
Ethylene-glycidyl methacrylate-vinyl acetate copolymer Glycidyl group content: 0.93 mmol / g
Vinyl acetate content: 0.58 mmol / g
Vicat softening point; 66 ° C
Resin C:
Ethylene-glycidyl methacrylate copolymer Glycidyl group content; 0.93 mmol / g
Vicat softening point: 75 ° C
Resin D:
Ethylene-glycidyl methacrylate-vinyl acetate copolymer Glycidyl group content; 0.47 mmol / g
Vicat softening point: 83 ° C
Resin E:
Ethylene-glycidyl methacrylate copolymer Glycidyl group content; 1.47 mmol / g
Vicat softening point: 53 ° C

(Polyamino compound)
Polyethyleneimine (Nippon Shokubai "Epomin SP-103")
Molecular weight; 250

(Quaternary ammonium agent, solvent, etc.)
Quaternary ammonium agent: methyl iodide (manufactured by Tokyo Chemical Industry)
Special grade hexane (Wako Pure Chemical Industries)
Sodium sulfite (Wako Pure Chemical Industries)

<Example 1>
A cylindrical die was attached to the tip of a 65 mm extruder. This cylindrical die has an outer mold and a core mold as shown in FIG. 1 at the lower end, and has a structure in which the outer mold and the core mold rotate in opposite directions.
While the resin A was charged into the above extruder and heated and melted at 170 to 210 ° C., extrusion was performed through the cylindrical die, and a cylindrical product of an ion exchange precursor net continuous downward was extruded. The extruded precursor net cylindrical product was guided to a mandrel (sizing) in a water tank, cooled and solidified, and then cut in the extrusion direction to obtain a continuous sheet of ion exchange precursor net.

The above sheet was immersed in polyethyleneimine and reacted at 110 ° C. for 20 hours. Then, quaternization reaction was carried out at 30 ° C. for 1 day in methyl iodide / hexane = mass ratio 40/60, and further immersed in a 0.2 N sodium sulfite aqueous solution to remove free iodine. Anion exchange nets were obtained (Sample Nos. 1-6). The an open area ratio per unit area (1 m ² ) of this anion exchange net is 50 to 56%, and the thickness is 0.63 to 0.80 mm.

About the obtained anion exchange net | network, the anion exchange capacity | capacitance and the moisture content were measured with the following method.
The obtained anion exchanger was immersed in a 0.5 N hydrochloric acid aqueous solution for 2 hours or more. Then, it was immersed in ion exchange water for 1 hour. Further, it was immersed in an aqueous 0.2 N sodium nitrate solution for 1 hour or more. The immersion liquid was subjected to precipitation titration with a 0.1 N aqueous silver nitrate solution, and the eluted chlorine ions were quantified (Pmmol).
The anion exchanger taken out from the aqueous sodium nitrate solution was immersed in seawater, washed thoroughly with ion-exchanged water, the liquid was thoroughly dropped, and the wet weight (W) of the anion exchanger was measured. Then, it dried at 60 degreeC overnight with the vacuum dryer, and measured the dry weight (D). From the above results, the anion exchange capacity and water content were calculated from the following formulas, the fixed ion concentration was further determined, and the results are shown in Table 1. The relationship between the Vicat softening point and the anion exchange capacity of the resin used is shown in FIG.

Anion exchange capacity (mmol / g) = P / D
Moisture content (%) = (W−D) × 100 / D

<Example 2 and Comparative Examples 1 and 2>
As shown in Table 1, except that the thermoplastic resin is changed from resin A to another type, the reaction is carried out by extrusion molding in the same manner as in Example 1, and the anion exchange net obtained in the same manner as in Example 1. Was evaluated. The results are shown in Table 1.

  From the above results, it can be seen that an anion exchange resin (anion exchange net) having a high anion exchange capacity and a high water content can be obtained by using a thermoplastic resin having a softening point of 70 ° C. or less.

<Reference Examples 1 to 4, Reference Comparative Examples 1 and 2>
As a thermoplastic resin, a blend of Resin C and Resin E, having various blend ratios (weight ratios) as shown in Table 2, and having various Vicat softening points is prepared. An anion exchange net was prepared in the same manner as in Experimental Example 1 except that the anion exchange capacity, water content and fixed ion concentration were determined. The results are shown in Table 2. In Table 2, the result of the comparative example 1 which used resin C independently was shown collectively. The relationship between the Vicat softening point and the anion exchange capacity of the resin blend used is shown in FIG.

  The above results also indicate that an anion exchange resin (anion exchange net) having a high anion exchange capacity and a high water content can be obtained by using a blend having a Vicat softening point of 70 ° C. or lower.

It is a figure which shows schematic structure of the die | dye used when shape | molding a net | network by extrusion molding. In Experimental example 1, it is a figure which shows the relationship between the Vicat softening point of the used thermoplastic resin, and the anion exchange capacity of the obtained anion exchange net | network. In Experimental example 2, it is a figure which shows the relationship between the Vicat softening point of the used thermoplastic resin blend, and the anion exchange capacity of the obtained anion exchange net | network.

Explanation of symbols

1: Outer mold 2: Core mold 1a, 2a: Groove to be a resin flow path

Claims (3)

In an anion exchange net consisting of an anion exchange resin formed in a net shape,
The anion exchange resin has a structural unit having at least one functional group selected from the group consisting of a glycidyl group, an epoxy group, and an acid anhydride group and a vinyl acetate structural unit, and the vinyl acetate structural unit Obtained by introducing anion exchange groups into the thermoplastic copolymer contained at a rate of 0.3 to 2.0 mmol / g, an anion exchange capacity of 1.5 mmol / g or more and a water content of 25% or more An anion exchange net characterized by comprising:   The anion exchange net according to claim 1, wherein the copolymer has an ethylene structural unit and a glycidyl methacrylate structural unit in addition to the vinyl acetate structural unit. The anion exchange net according to claim 1, wherein the fixed ion concentration determined by the following formula from the anion exchange capacity and water content is in the range of 6 to 10 mmol / g.
Fixed ion concentration = (anion exchange capacity / water content) × 100

Images