JPS5947647B2 - How to insert metal etc. into synthetic resin - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for inserting inorganic materials such as metals and ceramics, plastics, etc. (hereinafter sometimes abbreviated as metals, etc.) into synthetic resins. The purpose is to prevent cracks from forming.

BACKGROUND OF THE INVENTION There have been many articles in which metal or the like has been inserted into synthetic resin, such as tableware such as knives, forks, spoons, and pot lid knobs, and parts of various devices with inserts such as bolts and ceramics.

These are useful for achieving purposes such as insulation, heat insulation, aesthetics, and tactility. However, on the other hand, if the insert fitting comes off or rotates from the synthetic resin part,
Not only do they fail to achieve the above objectives, but their original functions are often lost as well. To prevent this, the insert metal fittings are made into a spiral shape or have irregularities. However, there were no good measures to prevent cracks, which is another drawback of insert products. Cracks occur due to stress concentration, and they are particularly likely to occur at the bonding surface between metals with different coefficients of expansion and synthetic resin.This not only impairs the aesthetics, but if left untreated, it can cause cracks in the synthetic resin part. Otherwise, the insert metal fittings may come off. The present invention is an insert method for preventing the occurrence of cracks, and its gist is that the part of the main body made of metal etc. that is bonded to the synthetic resin is inserted with a structure in which a groove is bored around the insert fitting (first step). Furthermore, in order to further ensure the achievement of the object of the present invention, there is a method (second invention) in which, in addition to having the above structure, a fibrous material is attached to the base of the insert metal fitting.

To explain the present invention with drawings, FIG. 1 shows a knife having a handle 3 made of synthetic resin, and FIGS. FIG. 2 is a diagram showing the inside, which is the key point of the present invention.

That is, in the conventional metal body 2, the surface from which the insert metal protrudes is flat, as shown in FIG. Grooves 6 and 61 are bored around the periphery of the grooves 6 and 61.
It is also possible to use a groove with a taper on the inside of 4' as shown in Fig. 4. Furthermore, the fibrous material is attached to the base of the metal insert as shown in FIGS. 4 and 5, and in particular, the one in FIG. 3 corresponds to that in FIG. 5. The reason why cracks can be prevented by drilling grooves is not clear, but it is possible that metal etc. and synthetic resin are bonded in an intricate manner rather than on a flat surface as shown in Figure 6. It is thought that this would make it difficult for stress to concentrate, and that it would be possible to further prevent stress concentration by interposing fibers in that area.

Further, by forming the groove, the contact area between the metal etc. and the resin becomes larger, so it is thought that the insert metal fitting becomes difficult to come off. The present invention is applicable to synthetic resins in general, and there is no distinction between thermoplastic resins and thermosetting resins.

Since cracks are likely to occur in thermosetting resins,
The effects of the present invention are particularly remarkable for melamine resins and phenolic resins. Conventional methods such as compression molding, injection molding, and transfer molding are commonly used for insert molding. The degree of difficulty in generating cracks depends on the type of synthetic resin as mentioned above, but it also depends on the thickness of the insert metal fitting and the thickness of the synthetic resin.

Therefore, the present invention does not mean that cracks will not occur regardless of the thickness of the synthetic resin, and even the present invention cannot prevent cracks from occurring if the thickness of the synthetic resin is extremely thin. Also, the deeper the groove, the more effective it is in preventing the occurrence of cracks, but if the groove is too deep, the synthetic resin will not flow and the synthetic resin will not penetrate deep into the groove, resulting in an incomplete molded product. There is a certain relationship between the thickness of the synthetic resin (d in FIG. 2) and the depth of the groove (h in FIG. 2) to prevent this from occurring. For example, in the case of melamine resin as a typical thermosetting resin h, 2>->0d (where d is 1 or more) is appropriate, and synthetic resins other than melamine resin also have a relationship similar to the above.

This can also be applied to the shape of the groove as shown in FIG. In order to further ensure the prevention of crack occurrence in the present invention, the fibrous material to be attached to the base of the metal insert may be either inorganic or organic, such as asbestos, glass wool, or long fiber cellulose.

To attach these to the metal insert, you can wrap a fibrous material around the metal insert to a certain width (Fig. 4a) and height (Fig. 4b), or wrap it to a certain thickness to satisfy Asb. You may cut out a non-woven fabric with intertwined fibers, etc. into a circular packing shape with the center hollowed out as shown in Figure 7, and insert it into the insert metal fitting, or if the insert metal fitting is short, you may wrap it around it, or use the same method as above. Methods similar to these may be adopted if they are effective.
In addition, when attaching the fibrous material to the metal insert, the fibrous material may be used as it is, or it may be impregnated with or adhered to a synthetic resin of the same quality as the synthetic resin to be molded so that the fibrous material is easily compatible with the synthetic resin. The present invention includes not only metals but also inorganic materials such as ceramics and ceramics, and plastics different from the synthetic resin to be inserted.

The insert method of the present invention completely prevents the occurrence of cracks in the synthetic resin part, and the contact area between the metal fittings and the resin is larger than in conventional methods, resulting in better adhesion.
The insert metal fittings do not come off and can withstand long-term use, while maintaining their aesthetic appearance.

The present invention is widely useful for various devices such as handles of tableware such as forks and spoons, knobs, handles of kettles, etc., as well as parts of electrical devices.

The present invention will be explained in detail below with reference to Examples, but the present invention is not limited thereto.

Example 1, Comparative Example 1 Groove (h/
A knife with d=1) was inserted into the melamine wood.

Melamine phenol resin (manufactured by Nikalets MPl Nippon Carbide Co., Ltd.) 359 was placed in a mold at 175°C, 200Kp/
Compression molding was performed using Ct7i. On the other hand, an insert knife was obtained by compression molding the knife 7 shown in FIG. 6, which has a flat adhesive surface with the synthetic resin, under the same conditions as above. :;:! The occurrence of cracks was observed in Table 1.ResultsExample 2, Comparative Example 2A punching-like plate shown in Fig. 7 was punched out from an asbestos plate into a knife with the groove type shown in Fig. 3, and the plate was inserted into the insert fitting. Insert molded.

At this time, the groove had h/d=1.2, and the asbestos board had an outer diameter of 5 mm and a thickness of 6 mm. Melamine resin (Nicalet MCl manufactured by Nippon Carbide Co., Ltd.) was used as the synthetic resin.
Compression molding was performed at 75°C and 200K'/Cd. A similar knife was also obtained by compression molding under the same conditions except that a knife as shown in FIG. 6 with a flat adhesive surface to the synthetic resin was used (no fibrous material was used). Table 1 shows the occurrence of cracks in both cases.
The results were obtained. After drying in a hot air dryer at 100°C for 30 minutes, take it out, immediately put it in water at 10°C to quench it, and leave it for 5 minutes.

This cycle is considered as 1 cycle, and 50 in 20 cycles.
Occurrence of cracks in the book.

[Brief explanation of the drawing]

FIG. 1 is a front view of the knife, FIGS. 2 and 3 are sectional views of the first embodiment of the present invention, and FIGS. 4 and 5 are sectional views of the second embodiment of the present invention. A cross-sectional view, Figure 6 is a cross-sectional view of the vicinity of a conventional insert fitting. The figure shows a perspective view of the fibrous material according to the second aspect of the present invention. 1...Knife blade, 2...Metal body, 3...Synthetic resin handle, 4, 4゜, 4゜'', 4''''...Outer edge of metal body, 5, 5', 5 '', 5'''...Insert fitting, 6,6°...Groove, T, T°...Fibrous material.

Claims (1)

[Scope of Claims] 1. When inserting a metal etc. into a synthetic resin, the part of the main body of the metal etc. to be bonded to the synthetic resin has a structure in which a groove is bored around the insert fitting as shown in the figure, and the insert is inserted by a conventional method. A method of inserting metal, etc. into synthetic resin, characterized by insert molding. 2. When inserting metal, etc. into synthetic resin, the part of the main body of the metal, etc. that will be bonded to the synthetic resin should have a structure with a groove drilled around the insert fitting as shown in the diagram, and then a fibrous material should be inserted into the base of the insert fitting. A method of inserting metal, etc. into synthetic resin, which is characterized by adhering it and then insert molding using a conventional method.