JPS58113225A - Processing of ion exchange membrane - Google Patents

Abstract

PURPOSE:To carry out in high productivity a processing of ion exchange membranes of good smoothness capable of adequate pressing at high temperatures, by pressing an ion exchange membrane sandwiched between parting supports consisting of heat-resistant films. CONSTITUTION:The objective processing can be carried out by sandwiching an ion exchange membrane[e.g. made from a fluoroplastic having carboxylic and/ or sulfonic acid group(s)]between parting supports consisting of heat-resistant films pref. endurable up to 1hr at >=150 deg.C (e.g. made from a saturated polyester resin) followed by subjecting to a flat-plate press or continuous roll press. EFFECT:Applicable also to thin ion exchange membranes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing ion exchange membranes, and more particularly to a novel press processing method for ion exchange membranes using a specific mold release support material.

Ion exchange membranes extruded into sheets from thermoplastic resins having functional groups such as sulfonic acid type groups and carboxylic acid type groups are subjected to secondary processing for various reasons. For example, fluororesin ion exchange membranes, which have been attracting attention recently, are generally manufactured by extruding thermoplastic resin into sheets, but irregularities occur on the membrane surface due to melt fracture phenomena. There are cases. In addition, unevenness may occur in km+ due to scratches caused by the extrusion die glue. Furthermore, in the case of a membrane kneaded with fibrillated fibers such as polytetrafluoroethylene, the tendency for the above-mentioned irregularities to occur during extrusion into a sheet increases. When unevenness occurs on the membrane surface, unevenness occurs in areas with uneven membrane thickness, resulting in local variations in membrane strength, and may also cause non-uniformity in the usability of the tear. This kind of ion exchange membrane is made by smoothing the unevenness of the membrane surface by heat pressing.
The thickness of the film can be made uniform by using the method, and the strength and performance of the film can be made uniform.

Therefore, the pressing process involves laminating two or more ion exchange membranes, laminating the ion exchange membrane with reinforcing cloth, or forming a special porous layer on the surface of the ion exchange membrane. It can also be effectively applied. In addition, press processing is
When the ion-exchange membrane is a fixed-sized product, it can be carried out using a flat plate press, and when it is a continuous long product, it can be carried out by a roll press, etc., as appropriate.

However, since the ion exchange membrane has a functional group, it has the disadvantage that it tends to stick to a flat mirror plate in a smoothing press or a metal roll in a roll press.

As a result, it is difficult to apply sufficient pressure at a sufficient temperature, making it impossible to process an ion exchange membrane with good smoothness with good productivity. Such adhesion makes it difficult to release the ion exchange membrane from the mirror plate or metal roll after pressing, and may cause the resulting membrane to tear or cause surface defects if it is forcibly removed.

The inventors of the present invention have discovered a method of press-working a heat-resistant film such as a polyester resin film or a fluororesin film by sandwiching a mold release support therebetween. Namely 1. In order to prevent the heat-resistant film from sticking to the mirror plate of the ion exchange membrane, it is possible to apply sufficient pressure at a sufficiently high temperature, and process ion exchange membranes with good smoothness with high productivity. be able to. By employing such a mold release support material, it is possible to carry out lamination pressing and the like in addition to smoothing pressing smoothly and advantageously.

Thus, the present invention provides a new method for processing an ion exchange membrane, which is characterized in that when pressing an ion exchange membrane, the ion exchange membrane is sandwiched between release supports made of a heat-resistant film.

It is provided to

In the present invention, it is important to use an orchid-shaped supporting material made of a thermoplastic film. As the heat-resistant film, one is selected that can sufficiently withstand the pressing temperature, for example, a saturated polyester side.

Polyamide resin, polycarbonate (Lw +
Density polyethylene, polypropylene, cellulose acetate,
Examples include plastic films made of polyimide resin and fluororesin. In addition, non-adhesive materials are preferable, and metal film-like materials such as aluminum foil may also be used after being subjected to non-adhesive treatment, for example. In addition, it may be a laminated film or a composite film, such as glass cloth, carbon cloth, metal cloth, heat-resistant paper, etc. impregnated with a fluororesin or laminated with a plastic film.

In a preferred embodiment of the present invention, the application of a fluororesin ion exchange membrane to press processing as described below is exemplified. In such a case, the heat-resistant film is a film that can withstand temperatures of 150°C or higher for up to 1 hour. preferable. For example, saturated polyester side fat such as polyethylene terephthalate, polytetrafluoroethylene, tetrafluoroethylene/hexafluoropropylene copolymer, ethylene/tetrafluoroethylene copolymer, polyvinylidene fluoride, polyfluoride Examples include heat-resistant plastic films made of vinyl, fluororesins such as ethylene/trifluorochloroethylene copolymers, tetrafluoroethylene/perfluorovinyl ether copolymers, and polyimide resins. Of course, such a heat-resistant film may be one that has been subjected to a stretching process such as biaxial stretching, or may be an impregnated or laminated film with glass cloth or the like.

Therefore, the thickness of the heat-resistant film can be selected from a wide range as long as it has sufficient strength as a release support material and does not impair the workability of press working, and is usually 12 mm thick.
-400μ, preferably from about 25 to 250μ. Further, the surface of the heat-resistant film may be appropriately modified, for example, the surface in contact with the ion exchange membrane may be roughened by blasting or the like. Such a roughened mud thermal film can suppress the inclusion of air bubbles when it is brought into close contact with an ion exchange membrane.

Next, examples of ion exchange membranes include those of the gods, but in the present invention, various types of press processing of fluorinated fat ion exchange membranes are particularly suitable. Naturally, it is made of thermoplastic resin. Application to a fluorine-111 fat ion exchange membrane is exemplified. The fluorine-containing ion exchange resin that makes up the ion exchange membrane includes carboxylic acid groups and sulfonic acid groups.

Resins made of fluorine-containing polymers having ion exchange groups such as phosphoric acid groups and phenolic hydroxyl groups are preferred. Such a resin preferably has a copolymer structure of a vinyl monomer such as tetrafluoroethylene or chlorotrifluoroethylene and a fluorovinyl monomer containing an ion exchange group such as a sulfonic acid, carboxylic acid, or phosphoric acid group. Further, a trifluorostyrene polymer having an ion exchange group such as a sulfonic acid group introduced therein may also be used.

In particular, it is preferable to use polymers having the following structures 0) and (b).

(() +CF2-CXX/ θ-, (b)
+CF2-CX Arrow here-1l'X is 1? ', CI
, H or -CF3te, X' is X or CFs (
CF2%, m is 1 to 5, and Y is selected from the following.

Z Rf x, y, z are all O to 10, and Z+ Rfij
-F and u are selected from perfluoroalkyl groups having 1 to 1[theta] carbon atoms. Also, A is -803M, -COOM or -8o2F which can be converted into these groups by hydrolysis.
, -CN, -COF or -COOR, M represents hydrogen or an alkali metal, and R represents an alkyl group having 1 to 10 carbon atoms.

In the present invention, the above-mentioned (a) and (b)
can be used in two or more types, and in addition to these,
Other ingredients such as ethylene, propylene.

Olefin compounds such as isobutylene, CF2=CF
Fluorovinyl ethers such as OQ (Qfd represents a perfluoroalkyl group having 1 to 10 carbon atoms).

CF2-CF-CF=CF2. CF2=CFO(CF
2) A fluorine-containing ion exchange resin containing one or more divinyl monomers such as 1-40CF=CF217) may be used.

The ion exchange membrane in the present invention preferably has an ion exchange capacity 1 of ld of 05 to 4.0 meq/g dry resin, particularly preferably 0.8 to 2.2 meq/g dry resin. In order to provide such an ion exchange capacity, in the case of a fluorine-containing ion exchange resin made of a copolymer consisting of the polymerized units of (a) and (b) above, preferably (
It is appropriate that the number of polymerized units in b) is 1 to 40 mol, particularly 3 to 30 mol. In addition, from the molecular weight of the ion exchange resin and the mechanical strength as an ion exchange membrane, T
When expressed as a value of Q, it is 170°C or higher, preferably 18
The temperature is preferably about 0 to 250°C.

In this specification, the term "TQ" is defined as follows. That is, TQ is defined as the temperature at which the volume fi' flow rate 1o o J/sec is related to the molecular weight of the polymer. Here, the volumetric flow rate is determined by using a polymer with an ion-exchange functional group of methyl ester type such as -COOCH3 group, and applying the polymer under pressure of -
Diameter of foot temperature I Wm + length 2- from orifice
・It shows the polymer cap that flows out and flows out in units of door 8/sec. In addition, the ion exchange capacity was determined as follows. That is, an acid type resin in which the ion exchange functional group is H type such as 1000H group is heated at 60°C in IN HCl.
The H-type resin was completely converted to H-type and thoroughly washed with water so that no H(J) remained.
．． 5 g, 0. IN NaOH 25mA to water 25mB
The mixture was incubated at room temperature for 2 days in a solution containing . Next, the resin was taken out and the amount of Na0HO in the solution was reduced to 0. IN
It is determined by back titration of HC1'''c.
Ru.

The ion exchange membrane in the present invention does not necessarily have to be formed from one type of polymer, nor does it need to have only ion exchange groups such as cypresses. For example, two types of polymers may be used in combination for the ion exchange capacity, or an ionic resin membrane may be used in combination with a weakly acidic exchange group such as a carboxylic acid group and a strongly acidic exchange group such as a sulfonic acid group.

Various press processes can be exemplified as the press process of the present invention. Examples include flattening, smoothing press processing, lamination press processing, transfer press processing, etc. of ion exchange membranes. These will be explained according to the attached drawings. FIG. 1 shows smoothing press processing using a flat plate press. In Figure 1 ■
is a hydraulic cylinder, ■ is a crown, ■ is a movable platen, ■
is a fixed platen, ■ is a tie rod, and ■ and @ are cushioning materials such as rubber or cardboard.

■ and 0 are mirror plates, ■ and [stock] are heat-resistant films.

■ indicates an ion exchange membrane, respectively. The ion exchange membrane (■) is sandwiched between two heat-resistant films (■) and [phase], and the mirror plates (■) and (2) and cushioning materials (■) and @ are stacked as shown in FIG. After pressing at room temperature to remove air, hot pressing is performed by heating the platens (1) and (2) for a predetermined period of time under pressure. Next, platens ① and ② are cooled. In this case, the press heating temperature can be selected from a wide range of conditions under which the ion exchange membrane is softened or melted, and can be selected depending on the type of resin constituting the ion exchange membrane. In the case of a flat plate press, the press pressure is 1 to 1000 monme, preferably 1 to 20 monme.
Approximately 0 monme is adopted.

FIG. 2 shows continuous smoothing press processing using a roll press. In Figure 2, ■ is an ion exchange membrane made into an extruded sheet, ■ and is a heat-resistant film as a release support material used to prevent adhesion, and ■, [stock], [phase] and h [phase] are tension detection. roll.

@ indicates a metal heating roll, [Co.] and q9 indicate a rubber press roll, [Co.] indicates a take-up nip roll, and ■ indicates a smooth press film winding roll. ■、■.

[stock] are each attached to an unwinding device, and the unwinding device is equipped with a tension detection roll qrS + Cvs-+ (t
It has a brake mechanism that detects the tension of the ion exchange membrane (2), the heat-resistant film (2), and the viper at ψ, and controls it to a predetermined tension. Two heat-resistant films ■.

The ion exchange membrane (■) sandwiched between the two sheets is pressurized by a metal roll @ and rubber press rolls (2) and (2), and subjected to smoothing press processing. The rubber press roll [phase], (19) is pressed against the metal roll @ with a predetermined force, and the metal roll @ is driven at a predetermined speed by a motor or the like. While detecting the tension, the speed of the take-up nip roll [Co., Ltd.] is controlled so that a predetermined tension is obtained.Then, the smoothed ion exchange membrane is wound onto the take-up roll. It is wound up while being sandwiched between two sheets of heat-resistant film, but if necessary, one or two heat-resistant films may be peeled off before winding up.

In the roll press, it is desirable to apply a sufficiently strong and controlled tension to the heat-resistant film in order to prevent thermal deformation of the heat-resistant film. In particular, it is desirable to apply a sufficiently strong tension to the heat-resistant film after it has been pressurized with the metal roll @ and the rubber press rolls (1) and (2). Usually 2011 or more per film width, preferably 1
A tension of about 00 to 5000 Ji' is employed.

By applying such tension, it is possible to prevent the occurrence of wrinkles and meandering of the film due to thermal deformation of the left side of the film #y, d under high temperatures. In addition, application of such tension prevents thermal deformation of the heat-resistant film, and at the same time, by controlling the tension with sufficient accuracy by detecting the tension, it is possible to minimize variations in the thickness of the ion exchange membrane.

Therefore, in the case of the roll press method, the pressing pressure is 0.5 to 200 per roll length I CAL using a pair of rolls.
kq + preferably about 1 to 100 kg can be adopted.

In addition, the press heating temperature employed in the flat plate press or roll press is selected from a range of 1 to 1 at which the ion exchange membrane softens or melts as described above, but it is preferable that the ion exchange In the case of an exhibition, usually 15
The temperature may be selected from a range of about 0 to 250'C, preferably about 180 to 230'C.

As described above, the heat-resistant film is used as a release support material to prevent adhesion, and the ion exchange membrane is reinforced with a method similar to the method of smoothing the ion exchange membrane using a flat plate press or continuous roll press. It can be laminated with commercial cloth, laminated with ion exchange membranes, and transferred various thin layers onto the surface of ion exchange membranes. These will be explained according to FIGS. 39, 42, and 5.

FIG. 3 shows continuous cross lamination pressing using a roll press. In Figure 3, ■ is a reinforcing cloth, ■ and [phase] are heat-resistant films, ■ are ion exchange membranes, □□□, [
stock], [phase], [phase] and O are tension detection rolls,
@ is a metal heating roll, ■ and ■ are rubber press rolls, [
Stock] H, nip roll for taking.

[Phase] indicates a cross-laminated film take-up roll.

FIG. 4 shows continuous lamination pressing of two ion exchange membranes using a Vi roll press. In FIG. 4, ■ and ■ are ion-exchange membranes, and ■ and (exclamation mark) are heat-resistant films. [Co.]', Ji and [Phase] are tension detection rolls, q7) is a metal heating roll, (1 second and Q4v are rubber press rolls, [Co.] is a nip roll for take-up.

(2) indicates the winding roll of the laminated ion exchange membrane.

FIG. 5 shows continuous transfer press processing using a roll press. In FIG. 5, ■ is an ion exchange membrane, ■ and qg are heat-resistant films with a porous thin layer formed on the surface, o,
te, [phase] and qO tension detection roll, @ is a metal heating roll, tl151 and time are rubber press rolls, ■ is a pull 1-1 nip roll.

(2) shows a winding roll of an ion exchange membrane on which a porous layer has been transferred. In this case, by replacing one of the ion-exchange membranes with a heat-resistant film, it is possible to obtain an ion-exchange membrane in which a porous layer is transferred to only one side of the ion-exchange membrane.

Of course, in the present invention, by using the methods shown in FIGS. 3 and 5 in combination, an ion exchange membrane having a reinforcing cloth h on one side and a porous layer transferred on the other side, or an ion exchange membrane having a reinforcing cloth h on one side and a porous layer transferred on the other side, or the method shown in FIGS. It is also possible to use these methods in combination to simultaneously perform the lamination of two ion exchange membranes and the transfer of porous membranes.

The ion exchange membrane to be pressed by the method of the present invention can be manufactured using the above-mentioned suitable fluorine-containing ion exchange resin or the like using various conventionally known or well-known membrane forming methods. However, such an ion exchange membrane may be a blended membrane of various types, and if necessary during membrane formation, preferably a fabric such as a cloth or net made of a fluorine-containing polymer such as polytetrafluoroethylene.

It may be reinforced with nonwoven fabric, metal mesh, porous material, or the like. In addition, in the press processing of the present invention, by employing a heat-resistant film, it is possible to carry out smoothly and advantageously even with an ion exchange membrane with a very small thickness, and usually the entire thickness is 20 mm.
~500μ.

An ion exchange membrane preferably having a thickness of about 80 to 300 microns may be employed as the object of press working.

Examples include films formed from an organic solution of a fluorine-containing ion exchange resin, an organic dispersion, etc. by a casting method, and films formed by heat melt molding such as press molding or extrusion molding. Of course, the fluorine-containing ion-exchange resin can be preliminarily heated and melt-molded into pellets, and the resulting pellets can be formed into 'JM 1=-' by extrusion molding, press molding, or the like.

During the heating melt molding or hot pressing in the present invention,
The fluorine-containing ion exchange resin constituting the ion exchange membrane is preferably in the form of an appropriate ion exchange group that does not cause decomposition of the ion exchange group it has, for example, in the case of a carboxylic acid group, it is preferably in the acid or ester type. In the case of a sulfonic acid group, it is preferable to use the -8O2F type.

Next, embodiments of the present invention will be described in detail, but it goes without saying that the present invention is not limited by this description.

Example 1 Ion exchange capacity i 1.50 mm/gram dry resin (
CF2=CFO(CF'2)3COOCH
3(Z) copolymer with fibrillated fibers of polytetrafluoroethylene. The ion exchange membrane with a thickness of 280μ, which was deep-deepened by rz@% and extruded, has considerable irregularities on the H1 coating surface. The ion exchange membrane was measured using a dial pipe gauge (P manufactured by Ozaki Seisakusho) with a spherical measuring part of 5 ml in diameter and 2 ml in diameter.
-1 type), the thickness was measured at intervals of 25 cylinders, and the standard deviation value was δ-29.0.

This ion exchange membrane was smoothed and pressed using a flat plate press shown in FIG. 1 using a biaxially stretched polyester resin film (manufactured by Diafoil Co., Ltd., thickness 100 μm) as a heat-resistant film. While maintaining the ion exchange membrane at an initial pressure of over 20,
The movable and fixed platen temperature was raised from room temperature to 190"C, air was removed, and then molding pressure was 60 monme to 15
After pressing for 6 minutes, while maintaining the pressure at 60 monme,
It was cooled to 0°C and taken out from the press. The thickness of the obtained ion exchange membrane was measured in the same manner as above, and the standard deviation value δ was &2. Therefore, it can be seen that the film thickness variation of the ion exchange membrane is reduced to less than 100 and is smoothed.

Example 2 An ion exchange membrane with a thickness of 260 μm having the same surface irregularities as in Example 1 was smoothed using a roll press shown in FIG. 2 using biaxially stretched polyester resin films as in Example 1 as the upper and lower heat-resistant films. Processed by chemical press processing. Upper and lower surfaces 1
The tension of the thermal film is 500 g/m, the tension of the ion exchange mk is 150,! Set to i+, /am. The surface temperature of the metal heating roll is 220℃, and the surface temperature of the rubber press roll is 1.
The temperature is set at 50°C, and the pressure is 4QJ (9/cm).The circumferential speed of the metal roll is set at 20/min. The tension of the three-layer sheet is 2k
Finely adjust the speed so that it is g/m.

When the film thickness distribution before and after roll pressing is added, the standard deviation value δ is 262 and 9.5, indicating that the film thickness variation of the ion exchange membrane has been reduced to less than about i, and that it is a semi-slip type. understood. In addition, thermal deformation of the 1111 thermal film and ion exchange membrane was well prevented, and stable roll press processing was performed without wrinkles or meandering of the film.

Example 3 Tetrafluoroethylene and CF2=CFO(CF,)3C with ion exchange membrane t 1.40 me'V'fi
OOCH3 copolymer extruded into a sheet with a thickness of 220 mm
μ ion exchange membrane and polytetrafluoroethylene, two warp yarns of 150 denier, one weft yarn of 300 denier, warp yarn density of 27 per inch, weft yarn density per inch of width! 1137 leno weave reinforcing cloths were laminated continuously using a roll press shown in Figure 3 using biaxially stretched polyimide resin films (trade name: Kapton films with a thickness of 50 μm) as upper and lower heat-resistant films. The tension of the upper and lower heat-resistant films is 2oog/car, the tension of the ion exchange membrane is 150 i/cm, and the tension of the reinforcing cloth is 200 i/cm.
Set it to 77/1m. The surface temperature of the metal heating roll is set to 220°C, the surface temperature of the rubber press roll is set to 90°C, and the rubber press roll is pressed against the metal roll at a pressure of 20ky/reef. The circumferential speed of the Kinfly roll was set to 40 rolls/min, and the tension of the four-layer sheet of the nip roll for taking-up after pressing was 2 kg/2 kg/min.
The velocity was adjusted to be fine=V so that OII&.

Ion exchange 1 obtained by the above operations! l! The cross lamination condition of 4 to 4 was good. In addition, heat deformation of the heat-resistant film - ion climate membrane and sleeve strength cloth is well prevented.
Stable cross & processing was performed without wrinkles or meandering of the film.

Example 4 Tetrafluoroethylene with ionic capacity -It 1.70 mθq/l/ and CF2 == CFO (C'
2) a 200μ thick ion exchange membrane and ion exchange capacity made by adding 2.5% by weight of polytetrafluoroethylene fibrillated fibers to the COOCH3 copolymer and extruding it into a sheet! , 0.25% of fibrillated polytetrafluoroethylene was added to a copolymer of tetrafluoroethylene and CF2=CFO(CF2)3COOCH3 having 25 meq/g, and extruded into a sheet with a thickness of 30μ. The ion exchange membrane was continuously laminated and pressed using biaxially oriented polyester resin films (manufactured by Diafoil Co., Ltd., thickness 100 μm) as upper and lower heat-resistant films using a 10-refless machine as shown in FIG. The tension of the upper and lower heat-resistant films is s
OOi/m Set the tension of each of the two ion exchange membranes to 150 II/1.

The surface temperature of the metal fly heating roll was set to 225°C, the surface temperature of the rubber press roll was set to 150°C, and the pressure was 4 o kg/
Press it onto a metal roll at m. The peripheral speed of the metal roll is 2
Set to 51n/min. The speed of the taking-off nip rolls is finely adjusted so that the tension of the four-layer sheet of heat-resistant film/ion-exchange membrane/ion-exchange membrane/heat-resistant film after pressing is 3 kg/.

The laminated state of the ion exchange membrane obtained by the above operation was good, and thermal deformation of the heat-resistant film and ion exchange membrane was well prevented, and the film remained stable without wrinkles or meandering of the film. Roll press processing was performed.

Example 5 As a heat-resistant film with porous thin layers formed on the upper and lower surfaces by the roll press shown in the semi-sliding press process obtained in Example 2, SiC with a particle size of 3 to 9 μm was used as a heat-resistant film (d/#) 10±2
g Biaxially stretched polyester resin film with six-membered porous layer (manufactured by Diafoil Co., Ltd.: thickness 100μ)
Then, continuous transfer press processing was performed using a biaxially stretched polyester resin film (manufactured by Diafoil Co., Ltd., thickness 100μ) on which a porous layer was formed on the surface by applying 10±29 TlO2 with a particle size of 2 to 10μ per d.

The tension of the upper and lower heat-resistant films is set to 50097 cac, and the tension of the ion exchange membrane is set to 150.9/m.

The surface temperature of the metal heating roll was set to 170°C, the surface temperature of the rubber press roll was set to 130°C, and the pressure was 30 kg/
Press with a metal roll using tx. The peripheral speed of the metal roll is 2
Set at 0mm/min, the take-up nip roll is
The speed was adjusted so that the force applied to the three-layer sheet of heat-resistant film/ion exchange membrane/heat-resistant film was 2#/true.

The surface of the ion exchange rib obtained by the above operations has
The Tie and SiC porous layer formed on the heat-resistant film were successfully transferred by melting the ion exchange membrane. In addition, thermal deformation of heat-resistant films and ion exchange membranes is prevented.
Stable transfer press processing was performed without wrinkles or meandering of the film.

[Brief explanation of the drawing]

The accompanying drawings are schematic explanatory diagrams for explaining typical examples of the press working method of the present invention, in which FIG. 1 shows smoothing press processing using a flat plate press, and FIG. 2 shows continuous smoothing press processing using a roll press. Figure 3 shows continuous cross lamination press processing 1 using roll press.
Figure 4 shows continuous laminated L/S processing by roll press, Figure 5
1 and 2 respectively show continuous transfer press processing using a roll press. Also t

Claims (1)

[Scope of Claims] 1. A method for processing an ion exchange membrane, which comprises pressing the ion exchange membrane by sandwiching the ion exchange membrane between release supports made of a heat-resistant film. 2. The processing method according to claim 1, wherein the ion exchange membrane is a fluororesin ion exchange membrane having carboxylic acid groups and/or sulfonic acid groups. 3. The processing method according to claim 1 or 2, wherein the mold release support material is a heat-resistant plastic film that can withstand temperatures of 150°C or higher.