JP2675073B2 - Compression molding apparatus and compression molding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a compression molding apparatus for plastics and a compression molding method using the compression molding apparatus, and more particularly to compression molding of SMC (sheet molding compound).

<Prior art> SMC molded products have excellent appearance, water resistance, chemical resistance, mechanical strength, and high productivity. In recent years, in addition to bathtubs, water tank panels, etc., aero parts, trunk lids,
It is used in automobile parts such as bonnets. When using SMC for the above applications, it is most often compression molded. The molding die is usually composed of a fixed die having a cutout portion and a movable die, which are made of rope, and the clearance of the cutout portion is 0.01 to 0.10 mm. After charging a predetermined amount of SMC material, it is compression molded at 30-150 kgf / cm ² , 120-180 ° C. At this time, the SMC flows out of the mold from the clearance at a part of the cut-out portion and burr is generated. Since this burr is unnecessary for a molded product, it is removed by an appropriate means after molding, but it requires manpower and time, which hinders productivity. Also, if burrs remain attached to the cut-off part, when the molded product is released from the mold, especially if the end of the molded product is thin, the burrs adhering to the mold will pull it and the end will be damaged, resulting in defective molding. Cause productivity to be impaired.

Furthermore, in most automotive applications it is painted,
Pinholes, cavities and the like inside the molded product are often exposed at the portion where burrs have been removed, which causes pinholes, craters, etc. in the coating film, and significantly impairs the appearance.

In order to prevent burrs from occurring, the clearance at the cut-out portion can be reduced, but in a mold with a steel cut-out portion, if the clearance is reduced, both edges that make up the cut-out portion interfere due to thermal expansion. There is a risk of chipping, and the clearance cannot be reduced to the extent that burrs do not appear.

<Problems to be Solved by the Invention> The present invention solves the above-mentioned problems, and the edges of the fixed and movable molds do not interfere with each other, and the clearance is substantially eliminated in the chamfer formed by the both edges. An object of the present invention is to provide a compression molding device that does not have the above.

Another object of the present invention is to provide a compression molding device in which burrs do not remain on the edges of molded products, and a compression molding method.

<Means for Solving Problems> A compression molding apparatus of the present invention includes a first mold having a first edge on the outer periphery, a pair with the first mold, and a cutout portion on the outer periphery. An apparatus having a second mold having a second edge that mates with the first edge to form, wherein at least one of the first and second edges comprises plastic, the plastic Is characterized by having a thickness of 10 mm or more in both vertical and horizontal directions on a cross section in a direction orthogonal to the edge line formed by the plastic.

The compression molding method of the present invention comprises the first mold and the second mold.
Sheet using the compression molding apparatus of the present invention having the mold
Characterized by compression molding of the molding compound.

Here, the edge of the mold refers to a ridge and a side surface that come into contact with the mating mold.

As the plastic used for either edge of the biting part of the compression molding device of the present invention, the molding temperature,
There are thermosetting resins and thermoplastic resins having sufficient strength at the molding pressure, that is, thermosetting resins and heat resistant resins having a heat resistance of 140 ° C to 150 ° C or higher. Examples of the thermosetting resin include Bakelite, epoxy resin, phenol resin, melamine resin, urethane resin, thermosetting polyester amide (CP resin), and the like, and examples of the thermoplastic resin include polytetrafluoroethylene and polytrifluoro resin. Examples include ethyne. A thermosetting resin having a flexural modulus at 140 ° C. of 50 kgf / mm ² or more is preferable, and an epoxy resin and a thermosetting polyesteramide (CP resin: manufactured by Takeda Chemical Industries, Ltd.) are preferable.

Fillers and reinforcing fibers may be added to these plastics to increase hardness and strength, and polytetrafluoroethylene powder may be added to improve slidability. Further, in order to reduce the adhesion of burrs, silicone resin or polytetrafluoroethylene resin may be coated, or the surface may be metal-plated.

<Operation> When the steel edge and the plastic edge interfere with each other, the plastic side is scraped off, so that galling does not occur unlike the case of the steel edges. As a result, the clearance at the cut-off portion is sufficiently small to the extent that burrs do not appear. Plastic materials are more elastic than metals and have a large Poisson's ratio, so when the pressure in the mold increases, the small clearance is blocked by the deformation of the material, and a completely zero clearance state is realized. Is an important feature of the present invention, the strength of the plastic edge is ensured by setting the thickness in the vertical and horizontal directions in the cross section orthogonal to the edge line to 10 mm or more, and It is possible to reliably perform each of the above-mentioned actions.

Further, when the plastic edge is worn during use and the clearance of the bite portion is increased, the clearance can be made sufficiently small again by immediately replacing the plastic edge.

<Embodiment> An embodiment of the device of the present invention will be described with reference to FIG.

The fixed mold 1 and the movable mold 2 form a pair. In the compression molding state in which the movable mold 2 is lowered, a molding space 3 having a predetermined shape is formed as shown by a chain double-dashed line. Fixed mold 1
A plastic edge member 4 is provided around the molding space 3. The outer side surface of the plastic edge member 4 and the ridgeline of the upper end thereof form a fixed edge 4a. A protrusion 5 is formed around the molding space 3 of the movable mold 2,
The inner side surface of the protruding portion 5 and the ridge line at the lower end thereof are movable edges 5a.
Is composed. The fixed edge 4a and the movable edge 5a cooperate with each other to form a cutting edge.

The fixed mold 1 is attached to the press lower plate 7, and the movable mold 2
Is attached to the press upper plate 6, and the press upper plate 6 is
Driven by the ram 10. A guide pin 8 and a guide pin hole 9 which are fitted to each other for alignment are provided on the outer peripheral portion of the fixed mold 1 and the outer peripheral portion of the movable mold 2.

The edge member 4 is usually formed by molding a plastic into a predetermined shape, for example, a quadrangular prism, and then cutting this if necessary, and fixing it to the die peripheral portion. The size of the edge member is
From the viewpoint of strength, those having a thickness of about 1 to 10 cm (in the case of a square pole, vertical and horizontal, respectively) are used.

Further, as shown in FIG. 5, a surface 44 having an oblique inclination angle α may be formed from the ridge to the side surface of the plastic edge member 4. According to the test, no burr was generated when α = 1.5 ° to 2 °.

Means for attaching the plastic edge member 4 to the mold body may be mechanically fixed with screws, bolts or the like, or may be adhered with an adhesive, or may be directly cast, cast or compressed on the mold. The plastic portion may be formed by a method such as molding or discharge molding.

When molding SMC etc. using the mold of the present invention, burrs do not appear, so air pockets may occur in molded products with complicated shapes, but at this time, eliminate air in the mold It is also possible to use a so-called vacuum compression molding method in which the inside is evacuated and then the SMC is caused to flow.

FIG. 3 shows that the movable die 2 has a plastic edge member 41.
The edge of the fixed mold 1 is attached to the mold, and the edge is made of the same material as the mold.

FIG. 4 shows that the fixed mold 1 has a plastic edge member 42.
Attached to the movable mold 2 and plastic edge member
An example in which 43 is attached is shown. In this case, plastic materials having different hardness or elasticity can be adopted.

Next, examples of the method of the present invention will be described. As shown in Fig. 1, SM pre-weighed on the fixed mold 1
When C11 is placed and the movable mold 2 is lowered, the SMC fills the molding space 3 as shown in FIG. Both molds 1 and 2 are preheated to a predetermined temperature. When the pressing force of the ram 10 reaches a predetermined value, the descent of the ram 10 is stopped and the pressure is maintained for a predetermined time. The chemical reaction of SMC proceeds during this holding time. Then, the ram 10 rises to obtain a predetermined molded product 11 '. Examples will be described below.

Example 1 A molded product was produced under the following conditions using an SMC for automobile skin.

Molded product dimensions 300 × 300 × 2.5mm Molded product weight 400g Lower mold edge material Thermosetting polyesteramide (CP resin) Mold temperature 145 ℃ Deadline speed 2mm / sec Compressing pressure 100kgf / cm ² Keep time 120sec Burr-free molding Goods have been obtained.

Example: 2 Using a colored SMC having the following composition, a parabolic antenna having a diameter of 40 cm was molded.

Molded product size Diameter 40cm, average thickness 3.5mm Molded product weight 1,050g Lower mold edge material Thermosetting polyesteramide (CP resin) Mold temperature Upper / lower 150/140 ℃ Deadline speed 1.0mm / sec Compression pressure 80kgf / cm ² Keep time 150 seconds A burr-free molded product was obtained.

<Effects of the Invention> According to the present invention, a compression-molded product free from burrs is obtained, and the productivity is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state before SMC compression of an embodiment of the present invention, FIG. 2 is a view showing a compression completed state thereof, and FIG. 3 is a longitudinal section showing a compression completed state of another embodiment of the present invention. FIG. 4 is a vertical sectional view showing a compression completed state of still another embodiment of the present invention. FIG. 5 is an enlarged view showing a modified embodiment of the plastic edge member 4. 1,2 …… Mold 3 …… Molding space 4,41,42,43 …… Plastic edge 5 …… Movable mold protrusion 5a …… Movable edge 11 …… SMC 11 ′ …… before compression molding SMC during compression molding

Claims (2)

(57) [Claims] 1. A first mold having a first edge on its outer periphery, and a first mold which is paired with the first mold and which engages with the first edge to form a cutout portion on the outer periphery. In a device having a second mold with two edges, the first
Alternatively, at least one of the second edges is made of plastic, and the plastic has a thickness of 10 mm both in the vertical and horizontal directions on the cross section in the direction orthogonal to the edge line formed by the plastic. The above is a compression molding apparatus characterized by the above. 2. A compression molding method, wherein a sheet molding compound is compression molded by using the compression molding apparatus having the first mold and the second mold according to claim 1.