JPS6054180B2 - How to manufacture plastic products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a surface protective coating on a plastic product.

Although the present invention is particularly effective when applied to reinforced plastic products having complex shapes, it is not limited to that use. In recent years, in the reinforced plastic molding process, a thin resin film for surface protection is formed on the surface of the mold in advance, and then the plastic is molded and hardened.

A construction method called the so-called gel coat method has become widely known. This method saves the effort of preparing the substrate compared to applying a protective coating after molding the product, but when used on a double-sided mold, defects in the adhesion of the protective layer tend to occur, and when used on a single-sided mold, Although the adhesion of the protective layer was excellent in this case, it had the disadvantage that the protective coating could not be applied to both sides of the product at the same time. In other words, in the case of double-sided molds, due to variations in the amount of reinforced plastic material placed between the upper and lower molds, the molding pressure applied to the reinforced plastic layer may be locally over or under, resulting in air bubbles remaining in areas where resin is insufficient. However, this causes poor adhesion and pinholes in the protective film due to internal air bubbles.

In addition, in the single-sided vacuum bag molding method, which is widely used in the aircraft industry and the general public due to its economical nature, the mold is only the lower mold, and the bag material for vacuum pressurization is made of flat plastic. Due to the use of film, this method is only applied to the lower mold side where it is easy to preform the gel coat layer, and the gel coat method to the bag side is
This process could not be carried out due to defects such as the appearance of wrinkles due to the coating falling off due to deformation during pressure molding of the film. However, when considering the uses of plastic products, there are
In practice, a protective coating is very often required.

For example, in chemical tanks placed near the coast or the rudder of an aircraft, a thin resin film is applied on both sides to improve seawater resistance, chemical resistance, sunlight resistance, lightning resistance, abrasion resistance, scratch resistance, and aesthetic appearance. It is common to apply any suitable surface protective coating, such as paint layer plating, vapor deposited or thermal sprayed metal film. The purpose of the present invention is to provide a method that can simultaneously apply a good gel coat to the bag side of a plastic product using an inexpensive single-sided type, thereby providing a defect-free protective coating on both sides of the product without using a double-sided type. It allows for the formation of

That is, the present invention includes a step of forming a surface protective coating on one side of a flexible bag material molded to match the shape of an uncured plastic product, one side of the uncured plastic product is in contact with the coating, and the other side is in contact with the coating. It is characterized by the process of placing one side in contact with a rigid mold and hardening it under pressure using fluid pressure, so there are no defects on the bag side without losing the advantages of the one-sided mold. It is possible to obtain gel-coated plastic products with no surface protective coating.

According to this method, the bag material, which also acts as a support for the gel coat layer, is not a flat plastic film, but has a shape close to the final state of the product, that is, a thick wall with air bubbles and excess resin extruded during molding. It is possible to eliminate problems such as cracking, chipping, and wrinkles of the gel coat layer due to the use of flexible bag material that is molded into the product shape (the shape of an uncured plastic product) before the loss of heat. I can do it! In addition, fluid molding pressure is applied through this bag material, so the flexible molding surface of the bag material It gradually deforms and pushes out internal air bubbles and excess resin, while applying uniform molding pressure to the entire surface by closely contacting the Reinforced Plus 5 chip layer, making it possible to sufficiently extrude internal air bubbles even in areas where resin is insufficient. As a result, the protective coating is completely and evenly adhered to by the homogeneous base material with no internal defects, so it is free from defects and does not peel off during use. 4. The material of this bag material can be appropriately selected from flexible materials such as rubber or soft plastic.

It should be noted that, instead of performing mold release treatment depending on the chemical composition of the protective coating, it would be more convenient to make the protective film from silicone rubber or the like, which itself is peelable, since the labor of mold release treatment can be saved. In addition, the lungs of the flexible bag material with an appropriate thickness are thin enough to be able to follow the above-mentioned fluid pressure and are easy to apply and handle to form a surface protective film. Dimensions are selected that have a thickness that allows for easy processing.

If it is too thick, the necessary deformation will not occur, resulting in local excesses or deficiencies in pressurizing force, similar to the mold. If it is too thin, the shape will collapse due to gravity, making it impossible to form a protective film layer on the surface.

The preferred thickness range depends on the hardness of the material, but generally it is about 1 mm to 10 mm, and for ordinary rubber molds it is about 3 mm.
Millimeter to 4mm was good. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows that on one side of a molded flexible bag material 1,
The process of forming a surface protective film is shown. The material and thickness of this coating are determined according to the purpose of use of the product, and in some cases, it is possible to have multiple protective coating layers. In this case, it goes without saying that the surface layer of the product should be coated first.
In addition, since the flexible bag material can sufficiently serve its purpose if it is molded into a shape close to the final state of the product, it is not necessary to mold it into the same shape as the final state of the product, making it economical. Furthermore, it will be more economical if the material is thick enough to withstand repeated use during the necessary pressure curing process, and is also peelable and does not require application of a release agent.
For example, when transferring zinc chromate paint to the surface of a reinforced plastic product molded with glass cloth and epoxy resin, we used a bag mold made of silicone rubber that can be vulcanized at room temperature and about 3 mm thick. Since the putty can be omitted, the weight is reduced by about 60g per square meter, and the labor cost is saved by about 6 man hours, which is a good result.

Furthermore, in the case of similar materials such as vinyl paint and PVA bag, or urethane paint and urethane rubber bag, the flexible bag itself may not be able to be peeled off later, so it is necessary to perform mold release treatment beforehand. Next, FIG. 2 shows a state in which a plastic material 3 is laminated on the rigid mold 2, and FIG. 3 shows that the flexible bag 1 of FIG.
It shows the state where it is placed and hardened under pressure.

In this step, the protective coating is pressure-bonded to the uncured product 3 through the entire surface of the flexible bag 1 without causing any cracks or wrinkles. The pressurization and heating are no different from the vacuum bag forming method that is normally practiced. Furthermore, we took advantage of the fact that the bag material is not a disposable thin synthetic resin film, but a flexible mold with a certain thickness, and created grooves that allow vacuum and suction on the surface that contacts the rigid mold, and a suction cup. The so-called 1 self-seal bag (Reference 1974 if SPI
(See collection of lectures) Alternatively, it is also possible to pressurize with a liquid or powder through a flexible bag, regardless of the pressure difference of a certain gas. FIG. 4 shows the molded and hardened plastic product 4 separated from both molds.

In this state, the protective coating has been transferred from the flexible bag material 1 to the surface of the product 4. Of course, by forming the necessary gel coat layer on the surface of the mold made of a rigid body, it is possible to simultaneously apply the surface protective coating to both sides of the product.

Further, even if the product is made of reinforced plastic alone, or a single-sided or double-sided sandwich product in which reinforced plastic is used as an outer shell and bonded to a lightweight core material, the advantages of the present invention will not be lost. Furthermore, even when the protective coating is a metal layer, the present invention can be carried out by ordinary industrial means such as metal spraying. Thus, according to the present invention, double-sided gel coating of plastic products using a single-sided mold, which was previously impossible, can be performed without any defects regardless of the complexity of the shape, thereby reducing product weight and manufacturing costs. reduction is possible.

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are sectional views sequentially showing steps in an embodiment of the present invention. 1... Flexible bag mold, 2... Rigid body mold, 3
...Uncured plastic product, 4...Finished plastic product.

Claims (1)

[Claims] 1. A step of forming a surface protective film on one side of a flexible bag material molded to match an uncured plastic product;
one side of the uncured plastic product is in contact with the coating;
1. A method for molding a plastic product, comprising the steps of placing the other side in contact with a rigid mold and hardening the product under pressure using fluid pressure. 2. The method for molding a plastic product according to item 1 above, characterized in that the rigid body is coated with a surface protective film in advance. 3. The method for molding a plastic product according to item 1 above, wherein the flexible bag material is itself a peelable material. 4. The molding method according to item 1 above, wherein the product has a sandwich structure in which a reinforced plastic outer skin is bonded to both sides of a lightweight core material.