JPH0446729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an in-mold molding method in which a foil material having a metallic luster or the like is provided on the front or back surface simultaneously with molding.

"Conventional technology" Traditionally, in-mold molding is a technology in which a foil material (in-mold film) is placed in a mold to mold a plastic product, and at the same time a metal layer is attached to the product to obtain a bright decorative object. In law,
Injecting synthetic resin material into the mold has been done using the general injection molding method, but since extremely thin foil material is used, there are limitations to the molding conditions such as injection pressure, injection speed, and temperature. However, the width of the application is narrow, and if the width is incorrect, the foil material may be misaligned, meandering, wrinkled, or the foil applied to the foil material and printing ink may flow, resulting in poor appearance as a product. rate becomes significantly higher. This problem is further aggravated by the complex shape of the molded product (the presence of irregularities or curved surfaces).

In other words, distortion of the molded product that occurs during molding due to the shape of the molded product (so-called sink marks), injection marks left on the molded product (so-called welds), and white areas caused by the presence of air in the molded product (so-called silver flash). ) etc. In this way, the shape of the molded product is limited, and at the same time, the foil material meandering and wrinkles occur, resulting in the flow of the foil applied to the foil material and the printing ink, etc. Consideration has been a significant bottleneck in providing high-quality, inexpensive products using in-mold molding.

"Problems to be Solved by the Invention" The present invention aims to provide a high quality and stable in-mold molded product regardless of the shape of the molded product.

``Means to solve the problem'' A foaming agent is uniformly mixed into the synthetic resin material for molding in advance, a foil material is set in the mold, and after the mold is clamped, an appropriate pressure is applied inside the cavity. Next, the synthetic resin material for molding is filled into the cavity space to a certain extent, and upon completion of filling, the pressure is returned to normal atmospheric pressure, and during this time, the outer surface of the filled resin material is At the same time as the layer begins to cool, internal pressure is generated in the inner layer of the filled resin material along with a foaming phenomenon, and the molded product is completed with the foil material tightly attached to the molded product.Then, the mold is opened and the molded product is finished. This is a method for producing a decorative body for a plastic product by simultaneous molding, which is characterized by taking out a plastic product.

"Function" When injection molding synthetic resin material mixed with a foaming agent into a cavity under pressure,
By filling approximately 95% of the hollow volume of the cavity, the foil material can be used after the pressure is removed, and the foaming energy of the foaming agent (generation of internal pressure) can significantly ease restrictions on molding conditions. As a result, the foil adheres to the molded product, which has a densely formed surface, in a very natural manner, so that the foil material is not damaged.

"Example" In mold A for molding shown in Fig. 1, A ₁ is male mold A ₂
is a female mold, and the foil material 1 is set in contact with the male mold _A1 . Here, 2 is a nozzle for injecting the synthetic resin material 3 for molding.

A foaming agent is uniformly mixed into the synthetic resin material 3 for molding in advance, and after the mold A is clamped, a pressure of about 20 kg/cm ² is applied to the cavity C, which is the hollow part of the mold A. Figure 2). In the figure, 4 is a valve that supplies and releases the pressure. Next, the molding resin material 3 mixed with the above-mentioned foaming agent is added to the space of 95% of the space volume of the cavity C.
% (Figure 3). When this filling is completed, the valve 4 is opened to release the pressure and return to normal atmospheric pressure. During this time, at the same time that cooling starts from the contact surface with the filling resin material in the mold A, a foaming phenomenon occurs in the molding synthetic resin material 3 mixed with the foaming agent, and the cavity C is filled with foam (Fig. 4). . In other words, this means that the synthetic resin material 3 for molding, which had been prevented from foaming until then due to the pre-applied pressure, starts foaming, and at that time, the inner layer of the synthetic resin material 3 for molding mainly foams. I will do it. The outer layer of the synthetic resin material 3 for molding has already come into contact with the inner surface of the mold A during injection, and its temperature has decreased somewhat compared to the inner layer and has begun to solidify, but due to the pressure of foaming. The entire outer layer of the synthetic resin material 3 for molding reaches the inner wall of the cavity C, and a surface layer is formed on the surface of the molded product, making the surface extremely smooth. Since it comes into close contact with the foil material 1 in this state, the contact and adhesion are performed in an ideal state without damaging the thin foil material 1. Next, mold A is opened and the molded product is product 5.
Take out (Figure 5). At the same time, the foil material 1 is reset.

According to this invention, when the synthetic resin material 3 for molding is injected into the cavity C, the injection pressure, injection speed, etc. can be set over a wide range by filling the cavity C with a filling amount of about 95% of its volume. It is. In other words, the present invention greatly relaxes the injection pressure, injection speed, etc. that are strictly regulated in the conventional in-mold molding method, and allows the synthetic resin material 3 for molding to be fed into the cavity C relatively gradually. , there is very little effect on the foil material 1 [thickness of about 25 to 50μ] due to the flow of the filled resin material, and there is no misalignment, meandering, wrinkling, distortion, etc. of the foil material, and the accuracy and appearance are improved. This makes it extremely easy to obtain in-mold molded products made of good foil material.

However, in conventional foam molding techniques, the foaming phenomenon also occurs on the surface, resulting in a roughened surface and poor adhesion of the foil material, making it impossible to obtain a product with good appearance.

The method of the present invention is not only capable of supplying a continuous in-mold foil material having a thickness of, for example, about 25 to 50μ, as shown in FIG.
It is also possible to manufacture products by setting a synthetic resin plate with a thickness of about 1000 μm in a mold.

"Effects of the Invention" According to the present invention, by significantly relaxing the molding conditions, the foil material is stably fixed and its adhesion state is extremely good. The in-mold molding method improves the yield of molded products and significantly reduces the defective rate (compared to the 5-20% defective rate for products made using conventional methods). You can easily obtain high-quality products.

In addition, by relaxing the molding conditions, there is no need for special in-mold foil materials as in the past, and ready-made foil materials can be used, making it possible to use various crystalline and amorphous thermoplastic synthetic resin materials. This means that a wide range of synthetic resins can be used, and a wide range of synthetic resins can be selected that are suitable for the adhesive layer of ready-made in-mold foil materials.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the state in which the mold is prepared for molding in this invention, Figure 2 is a diagram showing the state in which the mold is closed and pressure is applied, and Figure 3 is a cross-sectional view showing the state in which the mold is closed and pressure is applied. FIG. 4 is a diagram showing the state in which the pressure is released and foaming occurs, and FIG. 5 is a diagram showing the state in which the mold is opened and the product is taken out. 1... Foil material, A... Mold, A ₁ ... Male mold, A ₂ ...
...Female mold, 2...Nozzle, C...Cavity, 3...
...Synthetic resin material for molding, 4...Valve, 5...Product.

Claims (1)

[Claims] 1. Mix a foaming agent uniformly in advance with a synthetic resin material for molding, set a foil material in a mold, and after clamping the mold, apply a pressure of approximately 20 kg/cm ² in the cavity to complete the molding process. About 95% of the synthetic resin material for the mold is filled into the cavity space, and upon completion of filling, the pressure is returned to normal atmospheric pressure, and during this time, as cooling begins in the mold, internal pressure is generated due to the foaming phenomenon of the foaming agent. Therefore, a method for producing a decorative body for a plastic product by simultaneous molding is characterized in that the foil material is brought into close contact with the molded product.