JP2002273748A - Method for molding thermosetting resin molding compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily molding a large-sized thin thermosetting resin molded product, which is difficult to mold heretofore in a method for molding a molded product from a thermosetting resin molding compound low in resin content and low in flowability, with high accuracy. SOLUTION: In the method for molding the thermosetting resin molded product with a plane size of 200 cm<2> or more and a thickness of 2.5 mm or less, a composition containing a thermosetting resin and a base material is melted and kneaded by a heating roll to be taken out as a sheetlike molding material and this sheetlike molding material is subsequently processed so as to have a size being 40-100% of the plane size of the molded product and this processed sheetlike molding material is molded in a mold under heating and pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a thermosetting resin molding material having a small resin content and a low fluidity. An object of the present invention is to provide a method for easily and accurately molding an article. The molding method of the present invention is suitably used particularly for molding a fuel cell separator excellent in moldability and gas impermeability.

[0002]

2. Description of the Related Art Generally, when a molded article is to be obtained from a thermosetting resin molding material, compression molding, transfer molding or injection molding is performed using a crushed or granular thermosetting resin molding material. Alternatively, a crushed or granular molding material is once preformed into a columnar tablet, and the tablet is used for compression molding. However, when trying to obtain an unprecedented large-sized thin plate-shaped thermosetting resin molded product, the usual molding method may cause insufficient filling. In particular, when trying to mold a thermosetting resin molding material with low fluidity in which a base material or the like is blended more than usual, molding defects due to insufficient filling, poor appearance, insufficient strength, and molded product dimensions due to deformation of the mold. There has been a problem such as a decrease in accuracy.

As a method for solving the above problems, Japanese Patent No. 3008022 discloses a method in which a specific resin composite is preformed at a specific pressure and then further molded into a final shape. However, in this method, a large amount of voids are likely to remain between particles of the molding material of the preformed body due to insufficient molding pressure at the time of preliminary molding, and air in the voids cannot be sufficiently removed at the time of molding. Insufficiency occurs, for example, when a fuel cell separator is formed, there is a problem that strength and gas impermeability are reduced. In addition, since a step of forming a preform is required before forming into a final shape, a production cost is required.

[0004]

SUMMARY OF THE INVENTION The present invention aims at improving the above-mentioned drawbacks in a method for molding a thermosetting resin molded article having a small resin content and a low fluidity. An object of the present invention is to provide a method for easily and highly accurately molding a large and thin thermosetting resin molded product.

[0005]

The present invention provides (1) a plane size of 2
In a method for molding a thermosetting resin molded article having a thickness of not less than 00 cm ² and a thickness of not more than 2.5 mm, the composition containing the thermosetting resin and the base material is melt-kneaded by a heating roll, and is taken out as a sheet-shaped molding material. Next, the molded article is processed to a size of 40 to 100% of the plane size, and the molded article is heated and pressed in a molding die. (2) Thermosetting resin (1) The method of molding a thermosetting resin according to (1), wherein the base material contains 70 to 90% by weight of graphite with respect to the entire resin molding material. (3) Thermosetting resin molding The method for molding a thermosetting resin molding material according to the above (1) or (2), wherein the article is a fuel cell separator. In other words, instead of the conventional pre-formed tablet, the sheet-shaped molding material melt-kneaded by a heating roll is processed into a size of 40 to 100% of the planar size of the molded product and used.
The step of producing a preformed tablet is omitted, and the cost can be significantly reduced. In addition, it compensates for the insufficient filling, which was a problem when trying to mold a thermosetting resin molding material having a low fluidity in which the base material and the like were blended more than usual, and a surface that hangs on the mold cavity during molding. The pressure is more uniform compared to the conventional preformed tablet, so that the deformation of the mold can be suppressed. As a result, the plane size with excellent dimensional accuracy such as thickness is 200 cm ² or more, and the thickness is 2.5 mm or less. And a molding method for obtaining the thermosetting resin molded article of the present invention.

Hereinafter, the present invention will be described in detail. The present invention has a plane size of 200 cm ² or more and a thickness of 2.5 mm.
An object of the present invention is to provide a method for molding the following thermosetting resin molded article. Normally, it is difficult to form a molded product having such a shape with high dimensional accuracy, while for a molded product having a plane size of less than 200 cm ² and a thickness of more than 2.5 mm, the dimensional stability accuracy is determined by a normal molding method. This is because it can be molded well.

In the present invention, a composition such as a thermosetting resin, a base material, and a release agent is melted and kneaded by a heating roll, and a sheet-shaped molding material is used. It is characterized in that a thermosetting resin molded product having a plane size of 200 cm ² or more and a thickness of 2.5 mm or less can be formed at a lower cost compared to a method of forming a preform. Furthermore, for example, when a fuel cell separator is molded, the sheet-shaped molding material is rolled by rolls after melt-kneading, so that the gap between the particles of the molding material such as a conventional preformed tablet is small and remains in the gap. There is no reduction in moldability such as small blisters or insufficient filling due to the air and no reduction in gas impermeability associated therewith.

Next, the conditions for producing the sheet-like molding material will be described. In the present invention, the sheet-shaped molding material is obtained by melt-kneading a composition comprising a thermosetting resin, a base material, a release agent and the like with a heating roll. Although the temperature of the heating roll varies depending on the type and composition of the resin used, the molding material can be sufficiently kneaded, the kneaded material can be easily taken out as a sheet-like molding material, and the thermosetting resin can be kneaded at the time of roll kneading. Is set so that the fluidity during molding can be ensured. In the present invention, when the melt-kneading by the heating roll is insufficient, the composition can be mixed in advance with a Henschel mixer or the like to compensate for the insufficient kneading by the heating roll.

Further, in the present invention, the sheet-shaped molding material is processed to a plane size of 40 to 100% of the molded product. This is because the sheet-shaped molding material having such a plane size can compensate for the lack of fluidity of the molding material.
To describe an example of a specific processing method, a sheet-shaped molding material is taken out to a required width by a tentering plate or a roll cutter installed on a roll, and then cut to a required length for use.

The planar size of the sheet-shaped molding material is preferably 40 to 100% of the planar size of the molded product. If it is less than 40%, the peripheral portion may not be sufficiently filled even when a large and complicated thin plate-like molded product such as a fuel cell separator is molded. 100%
When the thickness exceeds, the planar size of the sheet-shaped molding material is larger than that of the molded product, and the molding material remains on the parting surface, so that sufficient thickness accuracy of the molded product may not be obtained. In consideration of the thickness accuracy and filling property of the molded product, the content is more preferably 70 to 100%. Further, the shape of the sheet-shaped molding material is not particularly limited, but is preferably similar to the planar shape of the molded product in order to further improve the filling property. Note that the average thickness of the sheet-shaped molding material is determined by the weight of the molded product, the size of the sheet-shaped molding material, the specific gravity of the material, and the like, and is not particularly limited. .

The difference between the maximum thickness and the minimum thickness of the sheet-shaped molding material is preferably 1 mm or less. When the difference between the maximum thickness and the minimum thickness is more than 1 mm, the uniformity of the surface pressure applied to the mold cavity during molding is lost, and particularly, a thermosetting resin having a low fluidity in which a substrate or the like is blended more than usual. In the case of a molding material, the mold is elastically deformed, and as a result, dimensional accuracy such as thickness may be reduced, or insufficient filling may occur locally in a portion where the sheet is thin.

The thermosetting resin used in the present invention is not particularly limited. For example, a phenol resin, an epoxy resin, an unsaturated polyester resin, a diallyl phthalate resin and the like are used. Among them, epoxy resin is preferable in terms of balance of dimensional stability, chemical resistance, and moldability, and as a fuel cell separator, cost, heat resistance,
Phenolic resins are particularly preferred in terms of the balance of chemical resistance.

When graphite is used as the base material in the present invention, the type of graphite is not particularly limited. For example, artificial graphite, natural scale graphite, earthy graphite and the like are used. Among them, as a fuel cell separator, conductive,
From the viewpoint of thermal conductivity and the like, artificial graphite and natural scaly graphite are particularly preferable. In addition, these graphites can be used in combination for the purpose of improving the conductivity and moldability of the fuel cell separator.

Further, when the molded article is used as a separator for a fuel cell, it is necessary to contain 70 to 90% by weight of graphite based on the whole thermosetting resin molding material. If the graphite content is less than 70% by weight, it becomes difficult to obtain the conductivity required for the fuel cell separator. If the amount of graphite is more than 90% by weight, the amount of graphite having low adhesion to the resin tends to be excessive, so that it is difficult to take out the molding material in a sheet form after kneading with a heating roll, and it is brittle even if it is taken out in a sheet form. In addition, since the fluidity during molding is small, poor filling is likely to occur, and it is difficult to obtain a large and thin molded article such as a separator. Considering the workability when forming the molding material into a sheet, the moldability and strength of the molded product, the more preferred amount of graphite is 75 to 85% by weight.

The sheet-like molding material obtained as described above can be put into a usual compression molding machine and molded. For example, a mold temperature of 140 to 200 ° C. and a molding pressure of 30
300 × 300 × 2m under conditions of 0~500kg / cm ²
A molded product having a size of m can be easily obtained.

[0016]

The present invention will be described in more detail with reference to the following examples.
However, the present invention is not limited by these examples. Further, “parts” and “%” described in Examples and Comparative Examples are all “parts by weight” and “% by weight”.
Is shown.

<Production of phenol resin> 100 kg of phenol (P), 87% paraformaldehyde (F)
60 kg (F / P molar ratio 1.64), zinc acetate 0.5 k
g in a 300 liter reactor equipped with a reflux condenser stirrer, a heating device and a vacuum dehydrator,
Time went. The phenol conversion at this point was 92%. Then, the mixture was heated to 115 ° C. while dehydrating, and further maintained at 115 ° C. and a degree of vacuum of 100 Torr for 1 hour. 100 kg of resin A (solid) was obtained.

Example 1 Resol type phenolic resin A
12 parts by weight, artificial graphite 85 parts by weight, release agent 2%, solvent 1
% Was kneaded with a heating roll (16 inches) at 80 ° C. for 2 minutes. The sheet-shaped molding material taken out with a thickness of 3.8 mm and a width of 220 mm was cut into a length of 220 mm to obtain a sheet-shaped molding material having a thickness of 220 mm x 220 mm x 3.8 mm. This sheet-shaped molding material is formed into a mold 300
mm × 300mm, placed at the center of a mold with a depth of 2mm,
Compression molding was performed at a mold temperature of 180 ° C., a molding pressure of 400 kg / cm ² , and a molding time of 3 minutes to obtain a molded product having a size of 300 × 300 × 2 mm. 53.7%). Table 1 shows the properties of the obtained molded product.

<Example 2> The size of the sheet-shaped molding material was set to 250 mm x 250 mm x 3 mm (6
9.4%) in the same manner as in Example 1.
A molded article having a size of 0 × 300 × 2 mm was obtained.

Example 3 Resol type phenolic resin A
10 parts by weight, artificial graphite 87 parts by weight, release agent 2%, solvent 1
% Of the composition containing 290 mm × 290 mm × 2.2 mm
Except for using a sheet-shaped molding material having a thickness (93.4% of the mold input area), the same method as in Example 1 was applied to 300 ×
A molded product having a size of 300 × 2 mm was obtained.

<Comparative Example 1> Except that the size of the sheet-shaped molding material was set to 180 mm x 180 mm x 5.7 mm (36.0% of the injection area of the mold), the same method as in Example 1 was adopted. A molded product having a size of 300 × 2 mm was obtained.

Comparative Example 2 Resol type phenol resin A
10 parts by weight, artificial graphite 87 parts by weight, release agent 2%, solvent 1
% Is kneaded with a heating roll at 80 ° C. for 2 minutes, and the obtained molding material is adjusted to an average particle size of 3 mm or less using an impact-type pulverizer or the like, and then is molded into a mold having a 290 mm × 290 mm cavity. Charged uniformly. Mold temperature is 60 ℃
The mold is clamped at a mold clamping pressure of 100 kg / cm ² for about 1 minute, and 290 mm × 290 mm × 2.2 m
An m-shaped preform was obtained. This preform is molded into a mold 30
0 mm × 300 mm, placed at the center of a mold having a depth of 2 mm, mold temperature of 180 ° C., molding pressure of 400 kg / cm ² ,
Compression molding was performed in a molding time of 3 minutes to obtain a molded product having a size of 300 × 300 × 2 mm.

<Comparative Example 3> The phenolic resin molding material having an average particle size of 3 mm or less obtained in Comparative Example 2 was used in a mold 300
mm × 300 mm, 2 mm deep, directly into the center of the mold, mold temperature 180 ° C., molding pressure 400 kg / cm ² ,
Compression molding was performed in a molding time of 3 minutes to obtain a molded product having a size of 300 × 300 × 2 mm.

Comparative Example 4 Resole type phenol resin A
4 parts by weight, artificial graphite 93 parts by weight, release agent 2%, solvent 1%
The composition containing was tried to form a sheet-shaped molding material in the same manner as in Example 1, but a good sheet-shaped molding material could not be obtained. Therefore, the kneaded product was unavoidably averaged in particle size using an impact-type pulverizer or the like. After adjusting to 3mm or less, mold shape 300mm × 3
It is directly poured into the center of a mold having a thickness of 00 mm and a depth of 2 mm, and is compression-molded at a mold temperature of 180 ° C., a molding pressure of 400 kg / cm ² and a molding time of 3 minutes to obtain a molded product having a size of 300 × 300 × 2 mm. Was.

The formulations used in the examples and comparative examples are as follows. 1. 1. Artificial graphite: average particle size 50 μm Release material: stearic acid Solvent: ethylene glycol

(Measurement method) Sheet property: A sheet obtained as a roll sheet which can be sufficiently processed into a predetermined size was evaluated as ○, and other cases were evaluated as ×. 2. Fillability: Completely filled was evaluated as ○, and even partially unfilled was evaluated as ×. 3. Thickness accuracy: The thickness at one point and four corners of the molded product was measured with a micrometer, and the difference between the maximum value and the minimum value was defined as the thickness accuracy. 4. Gas permeability: Measured according to JIS K 7126 A method. 5. Volume resistivity: Measured according to JIS K 7194.

[0027]

[Table 1]

In Examples 1 and 2, compared with Comparative Example 1, a sheet-like molding material having a plane size within the range described in claim 1 was used, so that the filling property was excellent and the thickness accuracy was good. A molded article can be obtained. Example 3 is Comparative Examples 2 and 3
In comparison with Comparative Example 3, since the form of the molding material is in the form of a sheet, it is excellent in gas impermeability, and further excellent in filling property,
A molded product having good thickness accuracy can be obtained. In Examples 1, 2 and 3, since the amount of graphite is within the range described in claim 2, the molding material is favorably processed into a sheet.
On the other hand, it is shown in Comparative Example 4 that if the upper limit of the range is exceeded, the sheet-shaped molding material cannot be realized.

[0029]

The present invention relates to a method for forming a large thin-walled molded product with high dimensional accuracy. Particularly, it is possible to obtain a molded product having excellent fluidity and excellent characteristics by compensating for the lack of fluidity of the material. It is a possible molding method. Therefore, even a molding material having low fluidity can easily and easily obtain a large-sized thin molded product with high precision, and the present invention can be used to form a fuel cell separator with good dimensional accuracy and gas. A fuel cell separator having good impermeability can be obtained. Further, since the step of manufacturing a preformed body is unnecessary and inexpensive, it is suitable as a more industrial method for forming a fuel cell separator.

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Claims (3)

[Claims] 1. A plane size of 200 cm ² or more and a thickness of 2.
In a method of molding a thermosetting resin molded product having a size of 5 mm or less, a composition containing a thermosetting resin and a base material is melt-kneaded by a heating roll, taken out as a sheet-shaped molding material, and then has a planar size of 40 mm. A method for molding a thermosetting resin molding material, which is processed to a size of about 100% and then heated and pressed in a mold. 2. The method for molding a thermosetting resin molding material according to claim 1, wherein the base material contains 70 to 90% by weight of graphite based on the entire thermosetting resin molding material. 3. The method for molding a thermosetting resin molding material according to claim 1, wherein the thermosetting resin molded product is a fuel cell separator.