JP2002248640A - Method for molding large-sized thin plate-shaped molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily mold a large-sized thin plate-shaped molded product with high accuracy in a method for molding the large-sized thin plate-shaped molded product from a thermosetting resin molding compound much in the content of a base material and low in flowability. SOLUTION: In the method for molding the large-sized thin plate-shaped molded product with a plane size of 200 cm<2> or more and a thickness of 2.5 mm or less from a thermosetting resin molding compound containing 80-95 wt.% of an inorganic or organic base material, a preformed molded object, which is molded so as to have a size being 95-100% of the plane size of the molded product and the thickness of the peripheral part of the molded object to the thickness 1 of the center part thereof of 1.1-1.4, is used to be subjected to compression molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily and accurately forming a large thin plate-shaped molded product using a molding material having a large content of a base material and low fluidity. The molding method of the present invention is suitably used, for example, for molding a fuel cell separator containing a large amount of graphite as a base material.

[0002]

2. Description of the Related Art Generally, when a thermosetting resin molded product is to be obtained, it is molded by compression molding, transfer molding or injection molding using a crushed or granular molding material. However, the base material content ratio is large,
When trying to obtain a large, thin plate-shaped molded product using a molding material with low fluidity, the usual molding method does not have sufficient fluidity and may cause problems in moldability. A method of forming a plate-shaped preform having a size of 40 to 100% of the product plane size and press-forming the preform in a molding die to prevent dimensional accuracy deterioration due to insufficient filling or deformation of the mold during compression. May be taken.

However, the content of the base material is 80 to 95% by weight.
In the case of a molding material that is highly filled with a base material such as that described above, the flowability is extremely small, so even with a method of molding using a plate-shaped planar preform, in order to ensure moldability, the molded product planar size A preform having an area of almost 100% of the above is required. However, when such a preform is put into a mold, there is no gap between the mold wall surface and the preform. It was not satisfactory.

In order to avoid such a problem, it is conceivable to reduce the size of the planar preform to 98% or less of the molded product so as to provide a gap between the mold wall surface and the preform. However, in this method, there are cases where the peripheral portion of the molded product is not filled or the central portion becomes thick.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a method of forming a large thin plate formed from a thermosetting resin molding material having a high content of a base material and a low fluidity, which has the above-mentioned disadvantages. It is another object of the present invention to provide a method for easily and accurately forming a large thin plate-like molded product, which has been difficult in the past.

[0006]

According to the present invention, a thermosetting resin molding material containing 80 to 95% by weight of an inorganic base material or an organic base material is prepared by using a thermosetting resin molding material having a plane size of 200 cm ² or more and a thickness of 2.5 m.
m, which has a size of 95 to 100% of the planar size of the molded product, and a thickness of 1.1 to 1. 4 is a method for molding a large thin plate-shaped molded product, which is performed by compression molding using a pre-formed body molded to be 4.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a molding material having a large content of a base material and a low fluidity during molding, and a planar size of 2%.
It is an object of the present invention to provide a method for molding a molded product having a thickness of not less than 00 cm ^{2 and not} more than 2.5 mm. Usually, it is difficult to mold a molded article having such a shape with high dimensional accuracy, while a molded article having a plane size of less than 200 cm ² and a thickness of more than 2.5 mm has a good appearance and a dimensional size by a normal molding method. This is because molding can be performed with high stability and accuracy. The present invention uses a preform that is equal to or slightly smaller than the plane size of the molded product to reduce the flow distance of the material during molding as much as possible, and makes the thickness of the preform thicker at the periphery and thinner at the center. By doing so, it is possible to provide a method for easily and accurately forming a large thin plate-like molded product.

[0008] The size of the preform must be as close as possible to the planar size of the molded product in order to complement the fluidity of the molding material. Therefore, the plane size of the preformed body is preferably 95 to 100% with respect to the formed product. Since it is better to secure a gap between the bodies, the plane size of the preformed body is more preferably 95%.
~ 98%.

A molding material having a low flowability filled with a high proportion of a base material tends to be insufficiently filled at the peripheral portion of the molded product when a planar preform is molded, and the peripheral portion has a small thickness.
In many cases, required thickness accuracy cannot be obtained. Therefore, assuming that the thickness of the central portion is 1, the thickness of the peripheral portion is 1.1 to 1.4.
It is preferable that the cross-sectional shape has a slope such that When the thickness ratio is less than 1.1, the peripheral portion may be unfilled, and when it exceeds 1.4, the thickness of the central portion tends to be thin and sufficient thickness accuracy may not be obtained.

The thickness of a molding material or molded article having a substrate content of more than 85% by weight and not more than 95% by weight is 1.0 mm or more.
Under conditions that are difficult to fill, such as less than 5 mm and a plane size exceeding 300 cm ² , the thickness ratio of the preform needs to be more strictly adjusted, and the thickness ratio of the preform is preferably 1. 2 to 1.3. On the other hand, under the condition that the thickness of a molding material or a molded article having a base material content of 80% by weight or more and 85% by weight or less and a thickness of 1.5 mm or more and 2.5 mm or less and a plane size of 200 cm ² or more and 300 cm ² or less is relatively easy to fill. The thickness ratio of the central portion to the peripheral portion of the preform may be selected in the range of 1.1 to 1.4 because the material has good fluidity.

The mold for molding the preform is usually provided with a cavity surface of the lower mold so that the thickness of the peripheral portion is 1.1 to 1.4 with respect to the thickness of the central portion of the preform. To process. The shape may be a quadrangular pyramid or a cone having an apex at the center thereof, or a shape in which the thickness is increased only at the peripheral portion. However, the shape is not particularly limited, and can be selected depending on the type of a molded product or a molding material. The upper mold may have a normal flat shape.
When the molding material is charged into the mold, it is desirable that the material be leveled in the lower mold before molding. If the input material is not flat, the density of the preform becomes uneven, and the thickness accuracy of the molded product cannot be obtained.

The thermosetting resin to be added to the molding material 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 can be used. The substrate is not particularly limited, but wood powder, glass fiber, glass beads, silica, graphite, and the like can be used.

As a method for producing the thermosetting resin molding material used in the present invention, an ordinary method is employed. That is, after adding and mixing a resin, a base material, and if necessary, a curing agent, a curing assistant, a pigment, a release agent, and the like, melt kneading with a heating roll or the like;

Next, the molding conditions for molding the preformed body will be specified. Since the molding of the preform must be performed at a low temperature at which the curing does not proceed, compression molding that can be molded without sufficiently melting the molding material is optimal. The molding temperature is preferably from 40 to 90 ° C. If the temperature is lower than 40 ° C., the adhesion between particles of the molding material is poor, so that it is difficult to form a large thin plate-shaped preform. On the other hand, when the temperature exceeds 90 ° C., the adhesion between the mold and the molding material increases, and the releasability of the preform is hindered. The molding pressure is suitably 200 to 300 kg / cm ² .

The thus obtained preform is put into a usual compression molding machine and molded. For example, mold temperature 1
70-200 ° C, molding pressure 500-800kgf / cm
^Under the condition ² , a molded product having a size of 300 × 300 × 2.0 mm can be easily obtained.

[0016]

The present invention will be described below in more detail with reference to examples.

Example 1 A phenol resin molding material comprising 85% by weight of graphite powder, 14% by weight of a resol type phenol resin and 1% by weight of a release agent (stearic acid) is used as a molding material. The particle size is adjusted to 3 mm or less in a production stage or a post-process using an impact-type pulverizer or the like. 350 g of this molding material is uniformly charged into a preforming die having a 290 × 290 mm cavity set at 60 ° C. and a lower die shape of a quadrangular pyramid. The upper mold is clamped at 300kgf / cm
² for about 1 minute to produce a preform having a center portion of 2.0 mm and a peripheral portion of 2.4 mm.
Placed at the center of a mold having a size of 0 × 300 mm and a depth of 2.0 mm, a mold temperature of 170 ° C. and a molding pressure of 300 kgf / cm
^2. Compression molding in 3 minutes molding time 300 × 300 × 1.
An 8 mm molded product was obtained.

<Example 2> A preform having a shape of 300 mm x 300 mm x 1.1 mm was used in the same manner as in Example 1 except that a preform having a shape of 2.1 mm at the center and 2.3 mm at the periphery was used.
An 8 mm molded article was molded.

Example 3 90% by weight of graphite powder, 7% by weight of resol type phenol resin, release agent (stearic acid) 3
A molded product having a size of 300 × 300 × 1.8 mm was molded in the same manner as in Example 1 except that a phenol resin molding material consisting of weight% was used.

Comparative Example 1 290 × 290 × 2.0 mm
A molded product of 300 × 300 × 1.8 mm was molded in the same manner as in Example 1 except that the planar preform was used.

<Comparative Example 2> The size of the preform was 270
X 300 mm in the same manner as in Example 1 except that
A molded product of × 300 × 1.8 mm was molded.

Comparative Example 3 Example 1 was repeated except that the thickness of the preform was 1.8 mm at the center and 2.7 mm at the periphery.
A molded product of 300 × 300 × 1.8 mm was molded in the same manner as in the above.

Table 1 shows the characteristics of the molded articles obtained in the examples and comparative examples.

[Table 1]

(Measurement method) Fillability: Completely filled was evaluated as ○, and even partially unfilled was evaluated as ×. 2. Thickness accuracy: The thickness at the center 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.

As is clear from Table 1, in Examples 1 to 3, the thickness of the preform is 1.1 to 1.2, and the area ratio of the preform to the molded product is 93%. Both fillability and thickness accuracy were good. In Comparative Example 1, since the planar preform was used, defective filling occurred in the peripheral portion, and the thickness accuracy was deteriorated. In Comparative Example 2, although the thickness ratio of the preformed body was 1.2, the area ratio was as small as 81%, so that the thickness accuracy was good, but filling failure occurred in the peripheral portion. Further, in Comparative Example 3, since the thickness ratio was set to 1.5, poor filling occurred at the center of the molded product, resulting in poor thickness accuracy.

[0026]

According to the present invention, an inorganic substrate or an organic substrate is used.
In a method of molding a thermosetting resin molding material containing 0 to 95% by weight into a large thin plate-shaped molded product having a planar size of 200 cm ² or more and a thickness of 2.5 mm or less, a size of 95 to 100% of the planar size of the molded product. Compression molding using a preformed body formed so that the thickness of the peripheral portion is 1.1 to 1.4 with respect to the thickness of 1 at the central portion. This is a molding method of a product, and can compensate for insufficient fluidity during molding in a thermosetting resin molding material having a large content of a base material, and can easily and highly precisely mold a large thin plate-like molded product. Thus, the present invention is suitable as an industrial molding method.

Claims (1)

[Claims] 1. A thermosetting resin molding material containing 80 to 95% by weight of an inorganic base material or an organic base material is prepared by a method using a flat plate having a plane size of 200%.
cm ² or more and a thickness of 2.5 mm or less in the method of molding into a large thin plate-like molded product, the molded product plane size of 95-10
It is characterized by being compression molded using a preform having a size of 0% and a thickness of 1.1 to 1.4 at a peripheral portion with respect to a thickness of 1 at a central portion. A molding method for large thin plate-like molded products.