JPS5938083B2 - Continuous forming method for graphite compacts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of stacking a plurality of flexible graphite sheets (hereinafter simply referred to as sheets), pressing them together and molding them.

More specifically, the present invention relates to a method of supplying an appropriate number of sheets between a pair of upper and lower forming rolls and continuously pressing them together to form a graphite molded body.

Graphite has excellent heat resistance, chemical resistance, and lubricity, and its sheet-like products are used as gaskets in various mechanical devices, automobiles, etc.
It is widely used in practical applications such as backing.

However, due to its excellent physical properties, there has been a strong demand for gutter-shaped or other irregularly shaped products, and the development of molded products that would make this possible has been desired from all walks of life.

Conventionally, when trying to obtain a gutter-like shape like a cylinder split vertically from a sheet of graphite, when a single sheet was deformed under pressure, the plasticity was extremely small due to the graphite's crystal structure, resulting in cracks and cracks.・It is known that wrinkles etc. may occur.

For example, a sheet with a density of i, o, y/= and a wall thickness of 0.5 mm will wrinkle when bent into a curved surface with a radius of curvature of 10 mm or less.
A sheet with a thickness of 1.5 mm will wrinkle if bent into a curved surface with a radius of curvature of 50 mm or less, and will break if the radius of curvature is 30 mm or less.

Similarly, as can be easily inferred from its crystal structure, graphite sheets have a small degree of stress relaxation, making it impossible to maintain the desired shape when external force is removed.

Therefore, instead of pressing and molding a single relatively thick graphite sheet, a method may be considered in which a suitable number of relatively thin graphite sheets are piled up and pressure molded.

In other words, by pressing and molding a plurality of graphite sheets into one piece, wrinkles and cracks do not occur, and the adhesive strength of each sheet allows it to maintain the desired shape even when external forces are removed.

However, when pressure forming multiple graphite sheets using the conventionally known mold press method, air remains between the sheets because the gas permeability of the graphite sheets is extremely low.
It comes as a blister.

In addition, in this case, the structure of graphite is a layered lattice made up of layers of six carbon terms.
Since the sheets are not crimped and integrated at all corresponding points, stress remains in the molded body.

This stress is not relieved, and therefore, after being removed from the mold, it cannot maintain the same shape as the mold.

Alternatively, in severe cases, the sheets may peel off from each other.

Furthermore, in such a molding method, the density is 1.8. ! il/cn
In order to obtain a molded product of about t, at least 400 kg/
Since a pressure of 800 to 1000 kg/d is required depending on the cvL and shape, an extremely large press is required and is expensive.

Furthermore, there is a major drawback in terms of labor and time, since graphite sheets must be supplied each time the molding is performed.

Therefore, the present inventors conducted extensive research to eliminate these drawbacks, and as a result, they arrived at the present invention.

Accordingly, one object of the present invention is to provide a method for obtaining a molded article free from blisters and residual stress caused by residual air when a plurality of thin graphite sheets are laminated and pressed and integrally molded.

Another object of the present invention is to provide the above-mentioned method which is economical and suitable for mass production of target products.

These and other features, features and benefits will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

According to the present invention, a graphite sheet stack consisting of a plurality of flexible graphite sheets is formed by a pair of upper and lower forming rolls each having a roll surface of a predetermined shape, and the crimping width of the stack is increased in stages. By continuously introducing the crimping roll between the crimping rolls with the largest crimping width of a plurality of crimping roll groups, and sequentially transferring the crimping roll to the crimping roll with the largest crimping width,
There is provided a method for continuously forming a graphite molded body, which is characterized in that the entire graphite sheet stack is integrated by pressure bonding while gradually widening the pressure bonding width.

The present invention will now be described with reference to the accompanying drawings.

FIG. 1 shows an example of the shape of a graphite molded body obtained by the present invention.

This molded article has a gutter-like shape with a width of 56 crf, a height of 44, a radius of the curved surface of the bottom of the basket of 24 mm, and a thickness of about 0.5 mm, and can be obtained by the apparatus 1 shown in FIG. 2.

FIG. 2 shows a schematic diagram of a continuous forming apparatus for graphite compacts for carrying out the present invention.

The graphite sheet 3 supplied from the graphite sheet supply rolls 2 2a 2b 2c is superimposed and guided between the lower forming roll 4 and the lower forming roll 5 that constitute the pressure forming roll, and is sequentially guided between the lower forming roll 4a and the lower forming roll 5. Forming roll 5a
The material is pressure-molded while being guided between the lower forming roll 4b and the lower forming roll 5b, and between the lower forming roll 4c and the lower forming roll 5c.

As a method of introducing a stacked graphite sheet, which is made by stacking a plurality of graphite sheets, into a pressure-bonding roll, it is possible to introduce a stacked graphite sheet in advance between the pressure-bonding rolls, or by introducing a stacked graphite sheet between the pressure-bonding rolls. They may be overlapped at the same time.

Each roll rotates at the same speed.

Lower forming rolls 5, 5a by roll gap adjustment handles 6° 6a, 5b, 6c.

By raising and lowering 5b and 5c and adjusting the distance between the lower forming rolls, the thickness, density, etc. of the molded product can be changed.

Although FIG. 2 shows a single-support type roll forming machine in which the roll is supported only on one side, a double-support type roll forming machine is preferred.

FIG. 3, FIG. 4, FIG. 5, and FIG. 6 show a lower forming roll and an enlarged front view of the lower forming roll.

The apparatus for carrying out the method of the invention is equipped with several sets of crimping rolls.

The lower forming rolls are shaped to match the shape of the intended molded product, and those having the same concave surface can be used.

The width of the suppressing convex surface of the lower forming roll is gradually increased so that the crimping width gradually increases.

For example, if the width of the first lower forming roll is such that the central part or one end of the sheet is crimped and integrated with a width of 10 to 20 mm, the second lower forming roll is 10 to 20 mm wider than that width.
Make the sheet 25mm wide enough to pressurize it.

The width of the pressing convex surface of the third lower forming roll is made wider so that the sheet can be pressed to a width 10 to 25 m1 wider than the crimping width of the second lower forming roll.

In this way, the width of the suppressing convex surface of the lower forming roll is gradually increased, and the width is finally set to be the same as the desired formed object.

Therefore, the larger the width of the molded body, the greater the number of rolls required.

The amount of increase in the width of the lower forming roll (Δmπ) can be appropriately designed as follows.

Flat part 20≦Δ≦30 The curved surface part varies depending on the radius of curvature (Rim), and R is 5
If 0mm or more, 181m≦Δ≦25imR is 35m
If rn ~50mm, 131m≦Δ≦20mm If R is 20mm to 35mm, 10 fights≦Δ≦17mrnR
is 10mm to 20mm, 8mm≦Δ≦13m5R
<10 mm, Δ-R However, the larger the central angle, the smaller Δ should be, and the smaller the central angle, the better Δ should be larger.

If the radius of curvature is R1 and the central angle is θ (however, θ<1600) is the standard, but Δ is 25r/1r
Do not exceed 11.

The sheet used in the present invention has a density of O,'#/cd~1
．． Og/i, preferably 0.8. ! 9/i~0.9. ! i
Use l/ffl.

If it is less than O,'#/cd, it will be brittle and crack easily, and if it exceeds 1.0,9/i, a skin layer with metallic luster will be formed on the sheet surface, and it will not self-adhesive even if it is pressed. Not only is it difficult to integrate due to poor adhesion, but the bonding strength is also weak.

The thickness is selected depending on the thickness and density of the desired molded object, but the thicker the sheet, the greater the brittleness, so when molding a curved surface with a small radius of curvature, a thick sheet cannot be used, and a large number of thin sheets must be used. Overlap.

Generally, one with a thickness of 0.25 to 0.4 mm is used.

In the present invention, the forming load (kg/crI
Table 1 shows the relationship between L) and compact density (9/=).

In order to properly press and integrate this sheet, the density of the molded product must be 1.0 g/ff1 or more.

Generally, the density of the compact is 0.2% compared to the density of the original sheet.
! 9/i9/i or preferably 0.25. ! The density and thickness of the sheet are selected so that it is greater than il/i.

This is the same even if a sheet with a high density of 1.59 g/i or more is used, but a sheet with a density of 1.5 g/i or more is 0.25 g/i or more. ! In order to increase the density by 7/CIrt or more, a large molding load is required.

The lower the density of a flexible graphite sheet, the more brittle it becomes and the easier it is to break when it is bent.

Therefore, if the density of the sheet is less than O,'#/cd, the sheet itself is likely to break.

In addition, when producing a graphite molded body with high density, many sheets with low density must be crimped together, so it is not rational for manufacturing to use a material sheet with a density of less than 0.7 g/cr/. .

Therefore, unless you want to obtain a molded product with a particularly low density (below 0,9,!lit/cI?L), the density is 0.79/cr/
! It should be avoided to use sheets of less than

On the other hand, relatively high-density compacts, e.g. density 1.8g
/C11t, wall thickness Q, if you want to obtain a molded body of 5 mrn, the density is 1.5. ! 9/i 3 sheets with a wall thickness of 0.2
Density 1゜Og/cril, wall thickness 0.3m than crimping one sheet
The crimping strength is greater when three sheets of m are crimped together.

According to the invention, the density is 0.7 to 1.11/cIi1. By using a sheet with a density of 1.0 to 1.8. ! il
A molded article of /i is obtained in good condition.

The thickness of the material sheet is determined by determining the density of the material sheet and the number of material sheets to be crimped from the density of the formed object and the thickness of the formed object.
．． Since it will be wrapped around 2a, 2b, and 2c, it is desirable that the thickness not exceed 0.5 mm in order to avoid bulk.

If there is a problem with the thickness, adjust the number of sheets to be crimped.

FIG. 7 shows a schematic cross-sectional view of another example of the shape of a graphite molded body obtained by the present invention.

In the case of a molded body having such a wave-shaped cross-sectional shape,
Pressure forming may be performed in stages from one end of the sheet to the other end.

For example, the height is 10 mrn, the length is 64 mm, and the radius of the curved surface is 2.
When obtaining a wavy molded body as shown in FIG. 7 with a diameter of 0 mm,
The first roll has a width of 16 mm crimped and integrated from one end, and the second roll has a width of 32 mm, which is the sum of the adjacent width of 16 mm to the part crimped and integrated with the first roll.

Further, the third roll has a width of 48 fins, and the fourth roll has a width of 64 fins.

FIG. 8 shows a preferred shape of the earth-acid roll used in the present invention.

By eliminating the corners of the ends of the suppressing convex surface in this way, it is possible to prevent streaks and scratches from forming on the molded article.

If the method of the present invention is carried out, the air existing inside the graphite sheets and between the sheets during molding will be exhausted, and at the same time, the corresponding parts of each sheet will be pressed together without any force, so no residual stress will be left and no swelling or swelling will occur. It is possible to continuously mold a molded product that does not rise and has substantially uniform wall thickness, density, and peel strength between sheets, and can be cut to the desired length by cutting it appropriately.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited to the Examples.

Example 1 Density 0. 'l/cyyt, thickness 0.25 mm, width 110 graphite sheets 3 are placed on graphite sheet supply rolls 2, 2a.

The upper forming roll 5 has a width of 15 mm, the width of 5a is 30 mm, and the width of 5b is 30 mm.
The four sheets were superimposed and fed between the pressure forming rolls of a continuous forming apparatus 1 having a width of 45 mm and a width of 5 cm.

At this time, the gap between the upper forming roll and the lower forming roll is determined depending on the thickness of the desired formed product, and in this example, the gap is 0.5 mm.
mm.

The density of the compact at this time is becomes.

In this way, the graphite sheets are formed from forming rolls 4 and 5 to 4a and 5a.
, 4b and 5b, 4c and 50 were molded under pressure in sequence.

In the forming roll 45, a width of 15 mm at the center of the molded body is crimped, and in the forming rolls 4a and 5a, 15 mm in width on both sides adjacent to the 15 mm width at the crimped center are formed by forming rolls 4 and 5.
is pressure-molded, and furthermore, on forming rolls 4b and 5b, a 15 mm wide portion on both sides of the outer side adjacent to the 30-mm width portion pressure-formed on forming rolls 4a and 5b is pressure-molded, and then on forming rolls 4c and 50, the remaining portion is pressure-molded. was pressure-molded, and the molding was completed.

The resulting molded body has a cross-sectional shape as shown in Figure 9a, and the peel strength between the second and third sheets of this molded body was measured using a Shimadzu Autograph 15-2000. As a result, a peel strength chart as shown in FIG. 9 was obtained.

AA/ indicates both ends of the trough-like molded body, B and B' indicate the transition from a curved surface to a flat surface, and C indicates the position of the lowest part of the molded body.

Comparative Example 1 A graphite sheet with the same density and thickness as the graphite sheet used in Example 1 was cut into pieces of 1101 m wide and 70 pieces long, and four sheets were stacked and press-molded using a conventional mold consisting of male and female sets. did.

The molded product obtained as a result had a cross-sectional shape as shown in FIG. 10a, and the peel strength of this molded product was measured in the same manner as in Example 1. A peel strength chart was obtained.

In the conventional pressing method using a mold, a minimum value appears on the chart due to residual air, but this is not shown because it is not quantitatively reproducible.

Comparative Example 2 A graphite sheet with the same density and thickness as the graphite sheet used in Example 1 was cut into pieces of 110 mm in width and 70 mm in length, and four sheets were stacked one on top of the other and pressed using a hydrostatic press method (Figure 12). Pressure molded.

The resulting molded body had a cross-sectional shape as shown in Figure 11a, and the peel strength of this molded body was measured in the same manner as in Example 1, and the results were as shown in Figure 11. A peel strength chart was obtained.

In FIG. 12, 7 is a graphite sheet, 8 is rubber, 9 is a mold (male mold), 10 is a frame material, and 11 is a liquid which is a pressure medium.

Although the hydrostatic press method provides ideal uniform pressure, it is not suitable for mass production or the production of long objects, and the equipment is expensive.

As is clear from the peel strength charts shown in Figures 9b, 10b, and 11, the method of the present invention is more suitable for mass production and requires less expensive equipment than the hydrostatic pressing method. Despite this, it is possible to obtain a graphite molded body with peel strength properties close to those of graphite molded bodies obtained by the isostatic pressing method, and far superior peel strength characteristics compared to the conventional mold pressing method. A graphite molded body having the following properties is provided.

Furthermore, the method of the present invention, like the isostatic pressing method, yields graphite compacts free of residual air.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the shape of a graphite compact obtained by the present invention, FIG. 2 is a schematic diagram of a continuous molding apparatus for carrying out the method of the present invention, and FIGS. 3, 4, and 5 6 and 6 are schematic front views of the pressure forming roll, and FIG. 7 is a schematic diagram showing another example of the shape of the graphite molded body obtained by the present invention.
FIG. 8 is a schematic diagram of a rounded upper forming roll preferably used in the present invention, FIG. 9a is a schematic cross-sectional diagram of a graphite molded body obtained by the present invention, and Peel strength chart, Figure 10a is a schematic cross-sectional view of a graphite molded body molded with a conventional mold, Figure 10 is a peel strength chart of the graphite molded body, and Figure 11a is a graphite molded body obtained by the isostatic pressing method. FIG. 11 is a peel strength chart of the graphite compact, and FIG. 12 is a schematic diagram of an apparatus for the hydrostatic pressing method. 1... Continuous molding device, 2, 2a, 2b, 2c.
...Graphite sheet supply roll, 3...Graphite sheet, 44a, 4b, 4cm lower forming roll, 5.
5a. 5b, 5c-earth acid rolls, 6, 6a, 6b. 6c...Roll gap adjustment bundle.

Claims (1)

[Scope of Claims] 1. A graphite sheet stack consisting of a plurality of flexible graphite sheets stacked one on top of the other is made up of a pair of upper and lower forming rolls each having a roll surface of a predetermined shape, and the crimping width thereof increases in stages. By sequentially introducing the crimping rolls between the crimping rolls with the smallest crimping width in a group of crimping rolls, and sequentially transferring the crimping rolls to the crimping rolls with the larger crimping widths, the crimping width is gradually widened and the crimping width is gradually increased. A continuous forming method for a graphite molded body, which is characterized in that the entire graphite sheet stack is crimped and integrated. 2. The continuous forming method of a graphite molded body according to claim 1, characterized in that the central part of the graphite sheet stack is first crimped, and the crimped width is gradually widened to both ends. 3. The continuous forming method of a graphite molded body according to claim 1, characterized in that one end of the graphite sheet stack is first crimped, and the crimping width is gradually expanded to the other end. .