JPS62244608A - Compression molding device - Google Patents

Abstract

PURPOSE:To keep the tip end of resin, spread by the force of compression, in vacuum and permit the obtaining of high-quality molded form stably by a method wherein an outer box is formed at the outside of the pinch-off section of a mold and the outer wall of the outer box is provided with sealing material to constitute the mold so as to evacuate the peripheral space of the resin. CONSTITUTION:A fixed mold 1 and a movable mold 2 are provided with mutually engaging edges 3, 4 at the outer peripheries thereof while these edges 3, 4 constitute the pinch-off section of seat molding compound (SMC). A fixed outer wall 7 is formed along the whole periphery of the outside of the fixed mold 1 and a movable outer wall 8 is formed along the whole periphery of the outside of the movable mold 2 while a loop-type seal material 9 is mounted on the movable outer wall 8. A loop-type outer box 10 is formed at the outside of both of the fixed mold and the movable mold under a condition that the fixed outer wall 7 is engaged with the movable outer wall 8 through the seal material 9. A vacuum evacuating pipe 11 is guided to an arbitrary position in the outer box 10 and is connected to a vacuum pump through a valve. The sealing material 9, provided with rubber elasticity at the temperature of 120-180 deg.C which is the molding temperature of the SMC, is employed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a compression molding apparatus for plastics, particularly for SM
Regarding compression molding of C (sheet molding compound).

<Conventional technology and its problems> SMC molded products have excellent appearance, water and chemical resistance.

In addition to its mechanical properties, it has good productivity, and in recent years it has been used for bathtubs,
Used in buttons, panels, automotive exterior parts, and outer panels. When used in the above applications, SMC is most often compression molded. A molding die usually consists of a movable die having a cut-off part and a fixed die. After opening the mold and charging a predetermined amount of SMC material, 30 to 150 kg/cs*
2. Compression molded at 120-180'C. At this time, the air in the mold and the air contained in the SMC are released from the cutout portion to the outside of the mold when the material flows, and a molded product with virtually no pinholes is obtained. However, this release of air is not perfect, and even when the SMC charging method and compression speed are taken into account, residual air sometimes remains in the molded product in the form of pinholes, cavities, blisters, cranks, etc., causing inconvenience. When molded products are given, the defective rate is high when compared to so-called injection molding of thermoplastic resin, especially SM
When a C-molded product is baked and painted like an automobile exterior panel, residual air expands and blows out during the paint baking process, causing defects such as pinholes, blisters, and craters in the paint film.
It seriously spoils the aesthetic appearance. On the other hand, JP-A-61-123
No. 10 discloses a technique in which air filling a lip hole formed in communication with a molding surface of a fixed mold is actively exhausted to the atmosphere while molding is performed. However, even with this method, when the SMC is rolled from the center to the periphery of the mold, the rib holes are quickly clogged, so that the remaining air in the mold is not effectively discharged.

The purpose of the present invention is to produce molded products of various shapes in which SMC spreads from the center to every corner of the periphery, such as a thin flat plate, a thin flat plate with ribs, or a box with a thin wall. It is an object of the present invention to provide a compression molding apparatus which can be commonly used for various types of compression molding apparatuses and which can effectively discharge residual air even when performing compression molding at a rapid rate.

Means for Solving the Problems> The compression molding apparatus of the present invention comprises a fixed mold having an edge on its outer periphery, and an edge that is paired with the fixed mold and engages with the edge of the fixed mold on its outer periphery. a movable mold forming a cutout portion; a fixed outer wall formed over the entire outer circumference of the fixed mold; and a fixed outer wall formed over the entire outer circumference of the movable mold and fitted with the fixed outer wall via a sealing material. and a vacuum exhaust pipe provided in an outer box formed by the fixed outer wall, the movable outer wall, and the fixed and movable molds, and the fixed outer wall and the movable outer wall are fitted together. It is characterized by that the cutout portion is configured to be in an unfitted state.

<Embodiment> FIG. 1 shows a state before SMC compression according to an embodiment of the present invention, and FIG. 2 shows a state after SMC is compressed.

The fixed mold 1 and the movable mold 2 have edges 3 and 4 on their outer peripheries that fit into each other, and these edges 3 and 4 constitute the cut-off portion of the SMC. The fixed mold 1 is firmly fixed to a fixed mold stand 5, and the movable mold 2 is firmly fixed to a movable mold stand 6. A fixed outer wall 7 is formed all around the outside of the fixed mold l, and a movable outer wall 8 is formed all around the outside of the movable mold 2, and a loop-shaped sealing material 9 is attached to this movable outer wall 8. and is fixed via this sealing material 9.

In a state in which the movable outer walls 7.8 are fitted, a loop-shaped outer box 10 is formed outside the fixed and movable molds. A vacuum exhaust pipe 11 is led out to an arbitrary position of this outer box 10 and communicates with a vacuum pump via a valve.

The sealing material 9 has a molding temperature of 120°C to 1
A material that has rubber elasticity at a temperature of 80°C is used.
For example, silicone rubber, urethane rubber.

Fluororubber, neoprene, butyl rubber, and NBR are used. This sealing material 9 may be fitted into a groove on the facing surface of the outer wall, or may be glued. Alternatively, a plurality of grooves may be provided and the position where the sealing material is fitted can be selected depending on the type of mold. You may.

As shown in FIG.
When the two edges are isolated from the outside world, edges 3 and 4 are not yet engaged and are in an open state. Note that the mold 1 may be configured such that the outer wall 5 is fitted inside the outer wall 6.
and the outer wall 7, or the mold 2 and the outer wall 8 may be integrally constructed.

When using this device, first place a predetermined amount of SMC approximately in the center of the fixed mold l, then lower the movable mold 2 and its mold stand 6, and as shown in FIG. becomes cut off from the outside world.

Here, when the valve leading to the vacuum pump is opened, the air between the outer box and the mold is evacuated, creating a vacuum state.

The degree of vacuum at this time may be 300-■H or less, preferably 150m-11g or less.
continues to descend, and the SMC is compressed and stretched until it reaches the compressed state shown in FIG.

Test Example 1 A molded article was made using SMC for automobile outer panels under the following conditions.

Charge amount 2.1kg SMC single i! 300g /300IX30C11 Charge size 600 x 400a++m 2-brie mold temperature Movable type / Fixed type -145°C / 140°C
Depressurization degree in the mold When the cut-off part contacts: 200mm
) When closing a 1 g mold: 30 Hg Closing speed 2 mm/sec Compression pressure 400 tons Keeping time 120 seconds A molded product with a wall thickness of 2.05 nuw and good surface smoothness was obtained. There are pinholes on the surface of the molded product due to residual air.

No blisters or cracks were observed.

Comparative Example 1 A molded article was made under the same conditions as Test Example 1 without reducing the pressure inside the mold. On the surface of the molded product, 5 pinholes with a diameter of 1 crane or less, 2 cavities, and 1 blister were observed.

Test example 2 A molded article was made using SMC for bathtubs under the following conditions.

Charge 4kg SMC weight! 300g /30cm Speed 1.5
A perfect molded product with no pinholes or color separation was obtained at a compression pressure of 1 ater/sec and a holding time of 300 tons for 180 seconds.

Comparative example 2 A molded article was made under the same conditions as Test Example 2 at normal pressure.

In addition to pinholes and blisters appearing on the surface, color separation occurred in some corners, and filling defects were observed at the tips of ribs and bosses.

Test example 3 245 molded plates were produced under the same conditions as Test Example 1.

No damage or wear was observed to the silicone rubber used for the seal.

The molded products in the above test examples and comparative examples were all 50
0w+s+

<Effects of the Invention> According to the present invention, an outer box is formed outside the cutout part of the mold, and a sealing material is provided on the outer wall of the outer box to evacuate the area around the resin. The expanding tip is always kept in a vacuum, making it possible to stably obtain high-quality molded products. In addition, since the mold is heated, it reaches a high temperature, but since the sealing material is located on the outermost periphery, the temperature is lower than that of the mold, making it possible to use a highly elastic and inexpensive sealing material, and the durability of the sealing material. Improves sex.

Furthermore, regardless of the shape and structure of the molded product, only one vacuum exhaust pipe needs to be installed at any position on the outer box, so even if the mold is replaced, the mold stand, outer box, and exhaust pipe are common. can be used. In addition, as mentioned above, the resin expands due to the compression force (the tip is always kept in a vacuum, so it is possible to increase the compression speed, improving productivity).

Incidentally, when the vacuum evacuation was not performed, the compression process required 15 seconds, but with the vacuum evacuation of the present invention, it was shortened to 5 seconds.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the state before SMC compression of the embodiment of the present invention, and FIG. 2 is a diagram showing the state when the compression is completed. 1...-Fixed mold 2-Movable mold 3.4--
Edge of cut-off part 5-・Fixed mold stand 6...Movable mold stand 7-
- Fixed outer wall 8 - Movable outer wall 9 - Seal material 10 - Outer box 11 - Vacuum exhaust pipe

Claims (1)

[Claims] a fixed mold having an edge on its outer periphery; a movable mold that is paired with the fixed mold and has an edge on its outer periphery that fits with the edge of the fixed mold to form a cut-out portion; and an outside of the fixed mold. a fixed outer wall formed over the entire circumference; a movable outer wall formed over the entire outer circumference of the movable mold and fitted with the fixed outer wall via a sealing material; the fixed outer wall, the movable outer wall, and the fixed movable molds. A compression molding device comprising a vacuum exhaust pipe provided in an outer box formed by a mold, and configured such that the cutout portion is in an unfitted state when the fixed outer wall and the movable outer wall are in a fitted state. .