JPS6144050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for molding a multilayer container molded from different resins, in which it is possible to very easily identify whether the thickness of each layer in the container has a desired thickness.

BACKGROUND ART Conventionally, multi-colored multi-layered molded products for the purpose of decorative effects, or multilayer containers simply laminated with different resins for the purpose of exhibiting composite physical properties, have been known. Various methods such as blow molding, rotary molding, and injection molding are known for obtaining these molded products.

The present invention is applicable to the above-mentioned various known methods, and provides a method for molding a multilayer container, which allows for faster, easier, and more accurate inspection of the layer thickness of a molded product. That is, when molding a multilayer container, the present invention colors each layer with a different pigment, and when light is projected, the color of the reflected light or transmitted light is observed and the color is determined appropriately for each layer. This feature is characterized in that it is possible to identify whether each layer of the molded product has the desired thickness by comparing the color with the color when the thickness is the desired thickness.

When molding a multi-layer container, if the designed thickness of each layer is considerably thick, even if the thickness of each layer of the multi-layer container is not formed as designed, there will be little problem in terms of performance. No special measures are required if the resin used has good fluidity. This is especially true when the multilayer molded article is intended for decorative effects.

However, if some of the layers are thinner than others, and the resin in the thicker layers has poor fluidity when melted, the thin resin layer may be It is extremely difficult to maintain a uniform wall thickness over the entire area of the molded product in order to achieve this effect. For this reason, molded products are often molded that do not exhibit the specified performance. Containers made of such non-uniform layers have been considered to be a very serious drawback when used as containers that require extremely strict gas barrier properties and solvent resistance, such as automobile gasoline tanks.

However, there has been no simple and accurate inspection method for distinguishing defective products from non-defective products. The present invention solves the above-mentioned problems, and thereby enables molded products such as gasoline tanks for automobiles to be manufactured with extremely reliable quality.

Examples will be described in more detail below.

Example An automobile gasoline tank was molded by the following steps.

(1) The inner layer of the tank structure, in which the tank was divided into three blocks, was formed from a white-colored 0.1 mm nylon-11 sheet by vacuum forming.

(2) The inner layer molded according to (1) was tightly charged into the male mold (core) of an injection molding machine.

(3) The mold of the molding machine was closed, and the black ultra-high molecular weight polyethylene that would form the outer layer of the tank structure was injected to obtain a tank structure with a thickness of 3 mm in which the outer layer and the inner layer were in close contact.

(4) A white light source was projected onto the molded tank structure from the inner layer side, and the color of the reflected light was observed.

As a result of observing a large number of tank components, approximately 99%
The whole surface of the tank structure was observed as a gray color, which is a mixture of white and black layers. However, about 1% of the tank structures were black near the injection molding gate, and It was confirmed that part of the inner layer was cut near the gate due to the heat and injection pressure of the injected resin in step 3), and that the inner layer had become extremely thin in some areas, and it was immediately checked as a defective product.

(5) The tank components that passed the inspection process in (4) were integrated using a high-frequency welder to obtain a gasoline tank.

The gasoline tank obtained as described above has extremely excellent chemical resistance and gas barrier properties,
Values of 1.1 gr/day·cm ² for gas barrier property and 150 Kg/cm ² for compressive strength (tensile strength of the welded part) were obtained.

Example 2 A tank was molded in the same manner as in Example except that an intermediate layer of adhesive was provided between the outer layer and the inner layer.

A 0.11 mm thick laminate sheet is obtained by coextruding 0.1 mm thick nylon-11 and Admer (unsaturated carboxylic acid modified polyethylene manufactured by Mitsui Petrochemicals). This sheet is used in step (1) of the example. In this case, the nylon layer is colored white and used on the inside, and the Admer layer is colored red and used on the outside (which becomes the intermediate layer).

Hereinafter, a tank structure was obtained in the same steps as (2) and (3) of Example. When a large number of molded tank structures were inspected, approximately 85% of them were observed to have a slightly dark pink color on the entire surface, confirming that the intermediate layer and inner layer were properly molded. However, the remaining 15% have black parts near the gate,
It was observed that the almost red parts were mixed together, and it was confirmed that the middle layer and inner layer were torn and the outer layer was mixed inside.

In the above embodiment, the method for forming a multilayer molded product was explained in which injection molding is performed on a preformed sheet, but the method of the present invention can also be applied to the case where a multilayer molded product is obtained by blow molding or rotational molding. . Further, the color combination is not limited to the above example, and any color combination that is easy to identify may be used.

Claims (1)

[Claims] 1. In a method for molding a multilayer container consisting of different resin layers, each resin layer is colored with a color that allows it to be determined by projecting light whether or not each layer is molded to a desired thickness; cast light on it,
By looking at the color of the reflected light or transmitted light and comparing that color with the color when each layer has the appropriate thickness, it is possible to determine whether each layer of the molded product has the desired thickness, and to identify defective or defective products. A method for forming a multilayer container characterized by distinguishing good products.