JPH0811241A - Fluoroplastic molded body for hydrogen storage and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a fluoroplastic molded body for hydrogen storage, which is excellent in heat resistance, thermal conductivity and the like, is hard to disperse through pulverization even after the repeated use over a long period of time and facilitates also the changing work of molded body by a method wherein a hydrogen storage alloy powder is dispersedly fixed in a fluoroplastic. CONSTITUTION:A hydrogen storage alloy powder is dispersedly fixed in a fluoroplastic or concretely 70-85wt.% of the hydrogen storage alloy powder is homogeneously dispersedly fixed in a fluoroplastic molded body. The hydrogen storage alloy is preferably an Mn-Ni based alloy and an Lm-Ni based alloy having normally 300-14 mesh particle diameter. Preferable fluoroplastic resin is PTFE, which has excellent hydrogen storage efficiency and flexibility withstandable against volumetric expansion (20-30%) and can be continuously used under the elevated temperature of about 200 deg.C over a long period of time. In order to mix the powder with the resin, blending is carried out in an inert gas atmosphere excluding nitrogen gas or dry blending in vacuum is carried out preferably. The homogeneous dispersed fixation of the powder in the resin is realized by firing their premolded material in an inert gas atmosphere excluding nitrogen gas or in vacuum.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fluororesin molded article for hydrogen storage and a method for producing the same, and more specifically, a fluororesin molded article for hydrogen storage which does not become pulverized and disintegrated even after repeated use over a long period of time and its production. Regarding the method.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION Hydrogen storage alloys are used in stationary tanks, hydrogen automobiles, etc. as storage materials for hydrogen, in mobile tanks for transporting hydrogen, and for heat generation / absorption during hydrogen storage / release. In addition to being used as a heat storage system as an energy conversion material used, it is used as a hydrogen separation / purification material, an electrode material of a secondary battery, a catalyst, a sensor, and the like.

In order to actually use such a hydrogen storage alloy, for example, when filling a hydrogen storage alloy in a tank, a shelf, a baffle plate, etc. are usually provided in the tank, and the shelf or the like is placed on the shelf. By pouring a powdery hydrogen storage alloy having a powder diameter of about 1 to 3 mm into the tank, the tank is uniformly filled.

However, such a powdery substance has a problem that it is difficult to take it in and out of the tank. Further, the hydrogen storage alloy usually has a hydrogen storage capacity of about 1 to 3% of the weight of the alloy, and generates heat during hydrogenation (hydrogen storage) of the alloy and causes a volume expansion of about 20 to 30%. When hydrogen is repeatedly stored and released, the above hydrogen storage alloy is pulverized and gradually collects at the bottom of the tank. In the hydrogen storage alloy thus accumulated in one place, the contact area between the hydrogen storage alloys is reduced, the thermal conductivity is reduced, and the hydrogen storage / release efficiency is also reduced. The finely-divided hydrogen storage alloy accumulated in 1) has a problem that the tank may be destroyed due to volume expansion.

Further, when the hydrogen storage alloy is pulverized, the thermal conductivity of the hydrogen storage alloy is lowered, and the hydrogen absorption / desorption reaction rate (response rate) is also reduced. Further, there is another problem that the finely pulverized hydrogen storage alloy is scattered and causes a trouble in the heat storage system such as clogging of a filter provided in a tank mounting portion or the like.

Therefore, it is desired to develop a hydrogen storage material which does not easily disperse into a fine powder even after repeated use over a long period of time, has excellent heat resistance and thermal conductivity, and does not cause troubles such as tank destruction. .

[0007] (1) Japanese Patent Publication No. 58-20881 discloses that "when absorbing and desorbing hydrogen by carrying out a reaction for producing a metal hydride composed of a metal and hydrogen and its reverse reaction, A method for absorbing and releasing hydrogen using a metal, which comprises using the metal hydride mixed with an oily substance which is liquid at room temperature. ] Is described. (2) Japanese Unexamined Patent Publication No. 57-14001 describes that a bundle of long fibers is placed in a container in which a metal hydride that absorbs and desorbs hydrogen and hydrogen gas are enclosed, and And a metal hydride reactor ”. (3) JP-A-58-223601 describes "a hydrogen storage element characterized by containing a hydrogen storage metal in a partially or wholly porous outer shell". It is described that plastic, rubber and the like can be used as the porous outer shell material. (4) "Hydrogen storage characteristics of hydrogen storage alloy resin moldings" (Chemical Engineering Symposium series 23, pages 100-105 (Nagoya Univ.) Watanabe et al.) Includes: Alloy and liquid phenolic resin on sponge body made of polyvinyl alcohol. After impregnating the mixture of the above, the molded product in the form of a structure, which is heat-treated at 393 to 453 ° K .: After molding a mixture of the particulate phenol resin, the liquid phenol and the alloy into a cylindrical shape,
Cylindrical shaped body, which is heat-cured at 0 to 430 ° K:
There is described a film-shaped molded product obtained by mixing alloy particles with a solvent-diluted solution of polyvinyl alcohol, vinyl acetate resin, resol resin, etc., thinly spreading the mixture in a mold, volatilizing the solvent, and then heat-treating as required.

However, in the above (1), it is not easy to replace the mixture of the metal hydride and the oily substance,
In (2), it is not possible to prevent pulverization and dispersion of the hydrogen-absorbing alloy powder, in (3) it is not easy to form a porous outer shell having a desired hydrogen-absorbing / releasing ability, and in (4), heat resistance is sufficient. However, if the hydrogen storage alloy resin molded body is thermally deteriorated and repeatedly used for a long period of time, the hydrogen storage alloy powder is pulverized and dispersed.

[0009]

It is an object of the present invention to solve the problems associated with the prior art as described above, and it is excellent in heat resistance, thermal conductivity, etc., and is finely dispersed even if it is repeatedly used for a long time. It is an object of the present invention to provide a fluororesin molded product for hydrogen storage that is difficult to perform and can be easily replaced, and a manufacturing method thereof.

[0010]

SUMMARY OF THE INVENTION The hydrogen storage fluororesin molding according to the present invention is characterized in that the hydrogen storage alloy powder is dispersed and fixed in the fluororesin. In a preferred embodiment of the present invention, in this hydrogen storage fluororesin molding, the hydrogen storage alloy powder is uniformly dispersed and fixed in the fluororesin molding in an amount of 70 to 85% by weight, preferably 75 to 80% by weight. Is desirable. Further, the fluororesin is
It is preferably polytetrafluoroethylene (PTFE).

The method for producing a fluororesin compact for hydrogen storage according to the present invention comprises mixing a hydrogen-absorbing alloy powder and a fluororesin powder, preforming the resulting mixture, and then firing the mixture.
The present invention is characterized by producing a fluororesin molded product in which a hydrogen storage alloy powder is dispersed and fixed in a fluororesin.

The hydrogen storage fluororesin molding according to the present invention as described above can be manufactured in any shape such as a cylinder or a plate, and such a molding can be stored in a tank or a shelf in the tank. Etc. may be provided, but they can be efficiently and uniformly arranged without any particular shelf, and the replacement work is easy. This molded product has excellent heat resistance and does not collapse due to thermal deterioration over a long period of time even when hydrogen is absorbed or released, so that the finely divided hydrogen storage alloy in the molded product may scatter. In addition, it does not cause clogging of the filter or the like, or destruction of the tank. Moreover, the thermal conductivity does not decrease.

According to the method for producing a fluororesin molded article for hydrogen storage according to the present invention, a molded article having any shape such as the above-mentioned columnar shape or plate shape can be obtained.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The fluororesin molding for hydrogen storage and the method for producing the same according to the present invention will be specifically described below. Fluororesin molded product for hydrogen storage In the fluororesin molded product for hydrogen storage according to the present invention, a hydrogen storage alloy is dispersed and fixed in the fluororesin.

As the hydrogen storage alloy, conventionally known ones can be used. Specifically, for example, Mg, V, N
Alloys such as b, La-Ni-based alloys, La-Co-based alloys, Sm-Co-based alloys, Mm-Ni-based alloys (Mm is a misch metal, that is, a mixture of La, Ce, and Sm),
Mg-Cu alloy, Mg-Ni alloy, Fe-Ti alloy, Mg-Al alloy, Ti-Al alloy, Ti-Mn
Alloys, V-Nb alloys, Lm-Ni alloys (Lm is
La-rich misch metal), Ca-Ni-based alloy, and the like.

Among these, Mm-Ni type alloy, Lm
A Ni-based alloy is preferably used. The powder size of such a hydrogen storage alloy is usually 300 to 14 mesh, preferably 240 to 48 mesh.

As the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP),
Examples include trifluorochloroethylene resin (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), vinylidene fluoride resin (PVDF), vinyl fluoride resin (PVF), etc., which have excellent heat resistance and are powder molded. Suitable for
E is preferably used. When such a fluororesin is used, it has excellent hydrogen storage efficiency (hydrogen permeability), has flexibility that can withstand volume expansion (20 to 30%) during hydrogen storage, is hard to collapse, and has a temperature of about 200 ° C. A hydrogen storage fluororesin molded product that can be continuously used at high temperature for a long time is obtained.

In this fluororesin molded product for hydrogen storage, it is desirable that the hydrogen storage alloy powder is uniformly dispersed and fixed in an amount of usually 70 to 85% by weight, preferably 75 to 80% by weight. Hydrogen storage alloy powder content is 70% by weight
When the content of the fluororesin exceeds 30% by weight, the hydrogen absorbed by applying a predetermined pressure cannot be released unless the pressure is lower than the pressure during hydrogen absorption. The hydrogen absorption / desorption efficiency may decrease (hysteresis increases), and if the content of the hydrogen storage alloy powder exceeds 85% by weight, in other words, if the fluorine resin content is less than 15% by weight, The hydrogen storage fluororesin molded product may collapse and the hydrogen storage alloy in the molded product may scatter when the absorption and release of is repeated over a long period of time.

In such a fluororesin molded product for hydrogen storage, it is presumed that the hydrogen-absorbing alloy powder is surrounded and fixed (is surrounded and fixed) by the fluororesin. Specific examples of the shape of the hydrogen storage fluororesin molding include a cylindrical shape, a cylindrical shape, a prismatic shape, a plate shape, and a spherical shape. Manufacture of Fluororesin Molded Product for Hydrogen Storage In the present invention, the above-described fluororesin molded product for hydrogen storage is manufactured by the following method. That is,
In the present invention, the hydrogen-absorbing alloy powder and the fluororesin powder are mixed, and the mixture obtained is preformed, and then the preformed product is fired, whereby the hydrogen-absorbing alloy powder is dispersed and fixed in the fluororesin. We manufacture fluoropolymer moldings. In detail, in order to mix the hydrogen storage alloy powder and the fluororesin powder, it is desirable to dry-blend in air, preferably in an inert gas atmosphere other than nitrogen gas (for example, in an argon gas atmosphere) or in a vacuum. . Further, in order to preform the obtained mixture into a desired shape, for example, a press molding method can be adopted.
A molding pressure of about 00 MPa is applied. After preforming in this way, if this preform is fired in an atmosphere of an inert gas other than nitrogen gas (eg, argon gas) or in vacuum, the hydrogen storage alloy powder is uniformly dispersed in the fluororesin. A fixed fluororesin molding is obtained.

The firing temperature of the preform is higher than the melting temperature of the fluororesin used (eg, about 325 ° C or higher for PTFE).
However, a temperature is adopted such that decomposition of the resin or oxidation of the alloy does not proceed remarkably, and depending on the type of fluororesin used, for example, in the case of PTFE,
Usually, it is fired at a temperature of about 340 to 380 ° C (eg, 370 ° C).

According to the method as described above, it is possible to manufacture a fluororesin molded article for hydrogen storage having any shape such as a columnar shape, a plate shape and a honeycomb shape. The hydrogen storage fluororesin molded product thus obtained can be efficiently and uniformly arranged and filled in the tank or the like without any particular provision of shelves, baffles and the like, and replacement work is easy. . This molded article has flexibility and heat resistance that can follow the volume expansion (20 to 30%) at the time of hydrogen absorption, and even when repeatedly absorbing and desorbing hydrogen over a long period of time, It will not be thermally deteriorated or collapsed due to heat generation, heating, etc. associated with hydrogen absorption and desorption. Therefore, it is possible to prevent the finely pulverized hydrogen storage alloy in the compact from scattering and clogging the filter or the like. Further, the scattered hydrogen storage alloy does not accumulate in the bottom of the tank, and the tank is not destroyed due to the volume expansion during hydrogen storage. In addition, in this fluororesin molded product for hydrogen storage, the hydrogen storage alloy is carried (held) by the fluororesin, and the hydrogen storage alloy does not pulverize and accumulate at the bottom of the tank. The thermal conductivity of the hydrogen storage alloy in the body does not decrease, and a decrease in the hydrogen absorption / desorption rate (response rate) is prevented.

[0022]

EFFECTS OF THE INVENTION In the hydrogen storage fluororesin molding according to the present invention, the hydrogen storage alloy does not pulverize and disintegrate and scatter even if it is repeatedly used for a long period of time.

[0023]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

[0024]

Example 1 Production of Fluororesin Molded Product for Hydrogen Storage Lm-Ni-based hydrogen storage alloy powder (powder diameter: 200 mesh under) and PTFE powder relative to 70% by weight of Lm-Ni-based hydrogen storage alloy powder. Dry blend the PTFE powder in an amount of 30% by weight in a vacuum and mix the resulting mixture to 15%.
After being preformed into a cylindrical shape under a pressure of 0 MPa, the preformed product is fired in vacuum at a temperature of 370 ° C. for 2 hours, so that the hydrogen storage alloy powder is uniformly dispersed and fixed in the fluororesin. Molded product (alloy equivalent: 3.75
g, dimensions: 15 mmφ × height 15 mm) were manufactured.

Table 1 shows the component composition of the fluororesin molding for hydrogen storage.

[0026]

Example 2 Production of Fluororesin Molded Product for Hydrogen Storage In Example 1, Lm-Ni based hydrogen storage alloy powder (powder diameter: 200 mesh under) and PTFE powder were mixed with L
PTF for 75% by weight of m-Ni-based hydrogen storage alloy powder
A fluororesin molded product (alloy-equivalent amount: 4.25 g, size: 15 mmφ × height 15 mm) was manufactured in the same manner as in Example 1 except that the E powder was used in an amount of 25% by weight.

Table 1 shows the component composition of the fluororesin molding for hydrogen storage.

[0028]

Example 3 Production of Fluororesin Molded Product for Hydrogen Storage In Example 1, Lm-Ni hydrogen storage alloy powder (powder diameter: 200 mesh under) and PTFE powder were mixed with L
PTF for 80% by weight of m-Ni-based hydrogen storage alloy powder
A fluororesin molded product (alloy conversion amount: 4.58 g, size: 15 mmφ × height 15 mm) was manufactured in the same manner as in Example 1 except that the E powder was used in an amount of 20% by weight.

Table 1 shows the component composition of the fluororesin molding for hydrogen storage.

[0030]

Example 4 Production of Fluororesin Molded Product for Hydrogen Storage In Example 1, Lm-Ni-based hydrogen storage alloy powder (powder diameter: 200 mesh under) and PTFE powder were mixed with L
PTF for 85% by weight of m-Ni hydrogen storage alloy powder
A fluororesin molded product (alloy conversion amount: 4.75 g, size: 15 mmφ × height 15 mm) was manufactured in the same manner as in Example 1 except that the E powder was used in an amount of 15% by weight.

Table 1 shows the component composition of the fluororesin molding for hydrogen storage.

[0032]

Example 5 Production of Fluororesin Molded Product for Hydrogen Storage In Example 1, Mm-Ni-Fe based alloy powder (powder diameter: 200 mesh under) was used in place of the Lm-Ni based hydrogen storage alloy powder. The Mm-Ni-Fe alloy powder and the PTFE powder were mixed with each other to form an Lm-Ni hydrogen storage alloy powder 8
A fluororesin molded product (alloy conversion amount: 4.78 g, size: 15 mmφ × height 15 m) was prepared in the same manner as in Example 1 except that the PTFE powder was used in an amount of 20% by weight relative to 0% by weight.
m) was produced.

Table 1 shows the component composition of the fluororesin molding for hydrogen storage.

[0034]

[Table 1]

[0035]

[Measurement of hydrogen absorption and desorption efficiency] 1. Measurement Method / Conditions Regarding the fluororesin moldings for hydrogen storage obtained in Examples 1 to 5, the end surface and burrs of the moldings were cut off to obtain φ1
5 mm x 6 mm (height) was cut out and used as a measurement sample. In addition, hydrogen equilibrium pressure-hydrogen (H) / alloy metal atom (M) composition ratio (H / M) isotherm (PCT line) measurement was carried out twice for each hydrogen storage fluororesin molded product. It was carried out twice, that is, after the hydrogen absorption and desorption was performed four times. Measurement conditions (a) Measurement temperature: 30 ° C.

(B) Activation conditions: For the samples shown in Examples 1 to 4, after evacuating at room temperature for 1 hour, hydrogen pressure was set to 30.
Atm was applied. For the sample shown in Example 5, the gas was evacuated at room temperature for 1 hour, and then hydrogen pressure was applied at 40 atm.

(C) Measurement of PCT line and hydrogen absorption rate:
It was based on JIS H7201,7202. 2. Measurement procedure (1) Activation of measurement sample: After vacuum evacuation (-a) of the sample at room temperature for 1 hour, hydrogen pressure was 30 atm (Example 1).
.About.4) or 40 atm (Example 5) was applied (-b) to activate the sample.

The time required for activation was about 40 minutes to 1 hour for the samples of Examples 2 to 4, and about 3 to 4 hours for the samples of Examples 1 and 5. (2) After activating the sample as described above,
Evacuate for a period of time (-a), then hydrogen pressure 30at
m (Examples 1 to 4) or 40 atm (Example 5) was applied (-b).

In the sample of Example 1, hydrogen absorption was completed in about 20 minutes. Moreover, in the samples of Examples 2 to 5,
The storage of hydrogen was completed in about 5 minutes. (3) First PCT measurement Next, for the samples shown in Examples 1 to 4, at room temperature,
After evacuating (-a) for 1 hour, apply hydrogen pressure of 30 atm
After (-b), the first PCT measurement was performed. this is,
This corresponds to the PCT measurement when hydrogen is absorbed and released 3 times (to) for convenience.

For the sample shown in Example 5, 1
After evacuation for a period of time, a hydrogen pressure of 40 atm was applied (-b), and PCT measurement was performed. The measurement was performed at 30 ° C. regardless of the sample.

The results are shown in Table 2. (4) Then, after evacuating (-a) at room temperature for 1 hour, the hydrogen pressure was 30 atm (Examples 1 to 4) or the hydrogen pressure was 40.
Atm (Example 5) was applied (-b). (5) Second PCT measurement Next, the second PCT measurement was performed. This corresponds to the PCT measurement when the hydrogen absorption and desorption was performed 5 times (to) for convenience.

The measuring method was the same as the first time. The results are shown in Table 2. In addition, the sample [Lm-Ni alloy 75
% Containing fluororesin molding for hydrogen storage]
The curve was determined. The result of the first measurement is shown in FIG. 1, and the result of the second PCT measurement is shown in FIG.

[0043]

[Table 2]

According to Table 2, especially in the sample (Example 1), the maximum hydrogen storage amount at the second time is remarkably increased as compared with the first time. It is considered that this is because, in the fluororesin molded product for hydrogen storage having a large content of fluororesin, hydrogen can be smoothly circulated in the molded product by repeating hydrogen absorption and desorption.

No change in shape such as cracking was observed in any of the above samples. In the above, although part of the alloy powder fell off from the hydrogen storage fluororesin molding, no drop of alloy powder from the hydrogen storage fluororesin molding was observed in any of (1) to (3).

Further, in the hydrogen storage fluororesin molded product according to the present invention, the hydrogen absorption after that is shorter than the time required for the initial activation of the alloy in the molded product, and once activated. Then, it can be seen that the subsequent hydrogen absorption / desorption is performed extremely smoothly.

[Brief description of drawings]

FIG. 1 is a PCT curve created based on the results of the first PCT measurement for a sample (Example 2).

FIG. 2 is a PCT curve created based on the results of the second PCT measurement for the sample (Example 2).

[Explanation of symbols]

1 and 2, the left vertical axis represents the pressure (atm), and the horizontal axis represents the atomic ratio (H) of hydrogen (H) and alloy atoms (M).
/ M) is shown.

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Claims (4)

[Claims] 1. A fluororesin molded product for hydrogen storage, comprising a hydrogen storage alloy powder dispersed and fixed in the fluororesin. 2. The fluororesin molding for hydrogen storage according to claim 1, wherein the hydrogen storage alloy powder is dispersed and fixed in an amount of 70 to 85% by weight. 3. The hydrogen storage fluororesin molding according to claim 1, wherein the fluororesin is polytetrafluoroethylene (PTFE). 4. A fluororesin molding in which the hydrogen storage alloy powder is mixed with the fluororesin powder, and the resulting mixture is preformed and then fired to disperse and fix the hydrogen storage alloy powder in the fluororesin. A method for producing a fluororesin molded product for hydrogen storage, which comprises: