JP2721392B2 - In-mold coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is to form an SMC material into a product shape,
The present invention relates to an improvement of an in-mold coating method for forming an in-mold coating layer on the surface.

(Prior art) Conventionally, as this kind of in-mold coating method,
For example, as disclosed in Japanese Patent Application Laid-Open No. 61-273921, first, an SMC material is placed in a molding die, pressed at a predetermined die pressure for a predetermined time and formed into a product shape. A method of forming an in-mold coat layer on the surface of the SMC molded product by injecting an in-mold coat layer forming material at a high pressure is generally well known.

Then, when the in-mold coat layer is formed by injecting the in-mold coat layer forming material at a high pressure,
In practice, the mold pressure (for example, 70 kg / cm ² ) of the mold is reduced to the mold pressure (for example, 30 kg / cm ² ) required for forming the in-mold coat layer, and in this state, the material for forming the in-mold coat layer is injected. It has been made to be.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional in-mold coating method, since the mold pressure at the time of injecting the in-mold coat layer forming material is rapidly reduced, the density of the SMC material is not uniform. When the material density becomes non-uniform as described above, the surface of the SMC molded product is not smooth due to the waving phenomenon, and the in-mold coating layer forming material injected into the molding die has the above-mentioned SMC molded product. However, there was a problem that the coating was not uniformly performed, and as a result, it was impossible to reliably obtain a product having excellent quality.

The present invention has been made in view of such a point, and an object thereof is to form an in-mold coat layer by appropriately controlling the mold pressure of a mold when injecting the in-mold coat layer forming material. Prevents the mold pressure from dropping rapidly during material injection, makes the density of the SMC material uniform over the whole, and eliminates the waving phenomenon of the SMC molded product, and therefore the in-mold injected into the molding die An object of the present invention is to uniformly coat the SMC molded product with a coating layer forming material to reliably obtain a product having excellent quality.

(Means for Solving the Problems) In order to achieve the above object, a solution of the invention according to claim 1 is to arrange an SMC material in a molding die and press it at a predetermined mold pressure for a predetermined time to form a product shape. A first pressing step for forming is provided. Furthermore, the SMC molded product having passed through the first pressing step is
A second pressing step of pressing at least once for a predetermined time at least in a state where the die pressure of the molding die is lower than the die pressure in the first pressing step is provided. Further, the second
While the SMC molded product that has passed through the pressing process is pressed with the mold pressure required for forming the in-mold coat layer, the material for forming the in-mold coat layer is injected into the above mold at a high pressure, so that the surface of the SMC molded product is in-mold coated. An in-mold coat layer forming step of forming a layer is provided.

Here, in the invention of claim 2, the mold pressure in the second press step in claim 1 is higher than the mold pressure required for forming the in-mold coat layer and lower than the mold pressure in the first press step. It shall be.

(Operation) According to the first and second aspects of the present invention, the SMC material is first placed in a molding die in a first pressing step and then pressed at a predetermined die pressure for a predetermined time. After being formed into a product shape and then pressed in the second pressing step at least once or more for a predetermined time with the mold pressure of the molding die being at least lower than the mold pressure in the first pressing step, In the mold coat layer forming step, while being pressed with the mold pressure required for in-mold coat layer formation,
An in-mold coat layer forming material is injected into the mold at a high pressure, and an in-mold coat layer is formed on the surface.

Therefore, the mold pressure of the molding die is gradually reduced over a plurality of stages until the in-mold coat layer forming material is injected, and is prevented from sharply decreasing during the in-mold coat layer forming material injection. The density of the SMC material is made uniform over the whole to eliminate the waving phenomenon of the SMC molded product, whereby the in-mold coating layer forming material injected into the molding die is uniformly coated on the SMC molded product. As a result, a high quality product can be surely obtained.

(Example) Hereinafter, an in-mold coating method according to an example of the present invention will be described with reference to FIG. 1 to FIG.

FIG. 1 is a process chart showing a procedure for forming an in-mold coat layer on the surface of a resin sheet material by the method of the present invention. First, an SMC material is prepared. As the SMC material, for example, an unsaturated polyester resin-based material is used, and its gel time is determined by the die pressure of the molding die B (shown in FIG. 3) in the first pressing step 1, that is, the primary pressure ( For example, 70kg / cm ² )
The cure time is set to 15 to 17 seconds from the start of holding, and the cure time is set to 80 seconds in a 150 ° C. atmosphere. At this time, the mold temperature of the molding die B was 150 ° C. for the upper mold b _{1 and} 145 ° C. for the lower mold b _2.
It is.

Next, the SMC material is subjected to the third pressing in the first pressing step 1.
As shown, set on the lower mold b ₂ of the mold B, 70 kg / c
Press for 5 to 15 seconds at a mold pressure of m ² , preferably 8 seconds before the transformation phase (gelation state) where the SMC material changes from a liquid phase to a solid phase as shown in the data diagram of FIG. Form into shape. The reason why the press time is set to 5 to 15 seconds is that if the press time is less than 5 seconds, the press becomes insufficient and the SMC molded product A
On the other hand, if the smoothness of the surface is deteriorated, a gelling state or a solid state occurs after 15 seconds, and a waving phenomenon appears in the SMC molded product A, or an in-mold coating layer forming material is formed on the in-mold coating layer C described later. This is because there is a possibility that an uncoated portion may occur.

Then, in the second pressing step 2, the first pressing step 1
The SMC molded product A which has passed through the above-mentioned process is in a state where the mold pressure of the mold B is higher than the mold pressure required for forming the in-mold coat layer C and lower than the mold pressure in the first press step 1, that is, 70 kg. Press for 12 to 32 seconds, for example, at a mold pressure in the range of 0.5 to 0.7 cm / cm ² . Thus, the mold pressure is reduced to 70 kg / cm ² × 0.5 to 0.7
The reason is that if it is less than 70 kg / cm ² × 0.5, the press will be insufficient and blisters will be generated on the surface of the SMC molded product A and the density of the material will be non-uniform, while exceeding 70 kg / cm ² × 0.7 This is because an uncoated portion of the in-mold coat layer forming material may be generated in the in-mold coat layer C.

Thereafter, in the in-mold coat layer forming step 3, the SMC molded article A that has undergone the second pressing step 2 is pressed at a mold pressure (for example, 30 kg / cm ² ) required for forming the in-mold coat layer C. An in-mold coating layer forming material C is formed on the surface of the SMC molded product A by injecting an in-mold coating layer forming material at a high pressure as shown by an arrow from a material discharge device (not shown) into the mold B, and this state is maintained for a predetermined time. Thus, a product D is obtained.

Thus, in this embodiment, first, the SMC material is first
In the pressing step 1, after being placed in the molding die B, it is pressed at a predetermined die pressure for a predetermined time to form a product shape.
In the pressing step 2, after pressing the molding die B for a predetermined time in a state in which the molding pressure of the molding die B is higher than the molding pressure required for forming the in-mold coat layer and lower than the molding pressure in the first pressing step 1, In the mold coat layer forming step 3, in a state where the mold is pressed with a mold pressure required for forming the in-mold coat layer C,
The material for forming the in-mold coat layer is injected into the mold B at a high pressure, and the in-mold coat layer C is formed on the surface of the SMC molded product A.
To form

Therefore, the mold pressure of the mold B is gradually decreased over two stages before the in-mold coat layer forming material is injected, thereby preventing the mold B from suddenly dropping during the in-mold coat layer forming material injection. Thus, the density of the SMC material can be made uniform throughout the entirety, and the waving phenomenon of the SMC molded product A can be eliminated. Therefore, the in-mold coat layer forming material injected into the molding die B can be uniformly applied to the SMC molded product A. To obtain a high quality product D without fail.

In the above example, the mold pressure of the molding die B in the second press step 2 was set higher than the mold pressure required for forming the in-mold coat layer and lower than the mold pressure in the first press step 1. In the state, the pressure is lowered in two stages, but the invention is not limited to this. For example, the mold pressure may be lowered in three or more stages. In addition, the timing may be appropriately determined according to the gel time of the SMC material.

(Effects of the Invention) As described above, according to the invention methods of claims 1 and 2, the SMC material is formed into a product shape, and when the in-mold coating layer is formed on the surface thereof, the SMC material is injected into the molding die. Before the mold coat layer forming material is injected, the SMC molded article is pressed at least once or more for a predetermined time while the mold pressure of the mold is at least lower than the mold pressure required for molding. Preventing a sharp decrease in mold pressure during injection of the mold coat layer forming material, the above-mentioned in-mold coat layer forming material can be uniformly coated on the above-mentioned SMC molded product, thereby reliably obtaining a high quality product. be able to.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a process diagram showing a procedure for forming an in-mold coating layer on the surface of an SMC molded product by the method of the present invention, and FIG. 2 shows a relationship between a mold pressure and a press time. FIG. 3 is a schematic configuration diagram of a molding die showing a state where the SMC material is molded into a product shape, and FIG. 4 is a longitudinal sectional view of a product on which an in-mold coat layer is molded. 1. First press step 2. Second press step 3. In-mold coat layer forming step A. SMC molded product B. Mold C. In-mold coat layer

Claims (2)

(57) [Claims] 1. A first pressing step of placing an SMC material in a molding die and pressing it at a predetermined pressure for a predetermined time to form a product shape; A second pressing step of pressing the die at least once or more for a predetermined time at least in a state where the die pressure of the die is lower than the die pressure in the first pressing step, and in-mold coating the SMC molded product having passed through the second pressing step An in-mold coat layer forming step of forming an in-mold coat layer on the surface of the SMC molded product by injecting the in-mold coat layer forming material into the mold at a high pressure while pressing at a mold pressure required for layer formation; An in-mold coating method comprising: 2. The mold pressure in the second press step is higher than the mold pressure required for forming the in-mold coat layer and lower than the mold pressure in the first press step.
The in-mold coating method described.