JPH0442978B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to a foam molding method, in which expandable thermoplastic resin particles are heated and fused in a mold cavity of a mold,
It concerns a method of manufacturing molded products.

<Prior Art> In the above foam molding method, the mold is very important in order to obtain a foam molded product with a desired shape.
Conventionally, a metal mold has been used as a mold, and the mold has good precision and excellent durability.

However, the above-mentioned molds have the disadvantage that they require technology to manufacture and are very costly. In addition, in the case of molds, there is a limit to the manufacturing dimensions, making it difficult to manufacture very large molded products, and there is also a limit to the capacity of the molding machine that carries out molding with the mold installed. It was impossible to produce molded articles. Furthermore, when manufacturing a mold, it is necessary to manufacture a wooden model in advance and then manufacture the mold by means such as casting or cutting according to the shape of the wooden model. It took a lot of time and effort to manufacture the mold.

Therefore, in the case of molds, the method is not cost-effective unless the amount of molded products produced is quite large, and the method is unsuitable for small-volume production of molded products with a small number of products.

It has also been proposed to use a mold made of gypsum or the like for vacuum forming foam sheets instead of the above mold, but gypsum has poor strength and is not suitable for bead molding where strong foaming pressure is applied. Although it was suitable, the mold accuracy was poor and it was impossible to manufacture large molds, making it impractical.

<Purpose> Therefore, the purpose of this invention is to solve the problems of the above-mentioned conventional technology and to develop a foam molding method that can easily produce large molded products and can also produce molded products in small quantities at low cost. It is said that

<Structure> In order to achieve the above objective, the outer surface of the prototype model is divided into two parts, and FRP resin is laminated separately along the outer surface of each part.
In the process of forming skin materials for a pair of molds, after joining a cross-shaped rigid frame to the back of each skin material, the space between the rigid frames is filled with a filler such as plaster. Step of reinforcing the back side and forming a pair of molds, introducing a filling nozzle from the outside of the mold into the cavity of the mold, and filling the cavity with expandable thermoplastic resin particles from this filling nozzle. After that, a heating probe is inserted into the mold cavity from the outside of the mold, and the resin particles are heated and fused using the heating medium ejected from the heating probe to produce a molded product. It is characterized by

<Example> Next, an example of the present invention will be described below with reference to the drawings.

1 to 5 show the manufacturing process of a surfboard core material as a molded product in the order of steps.

In Fig. 1, 1 is a prototype model, which can be formed by using the same wooden mold as before, by using the actual foam molded product manufactured in the past, or by cutting a block-shaped foam into the desired shape. It also does not require the precision and strength of wooden molds for traditional mold making.

Then, as shown in FIG. 2, uncured FRP resin is pasted along the outer surface of the prototype model 1, laminated to a certain thickness, and hardened to form the skin material 2. In addition, in the figure, the original model 1 is divided into upper and lower halves, and the upper and lower parts are separated.
A pair of upper and lower skin materials 2 are formed by laminating FRP resin. Further, a flange 20 extending horizontally is formed on the outer periphery of the skin material 2, and the upper and lower skin materials 2 are opposed to each other with the flange portions 20 in contact with each other.

After the skin material 2 is hardened and formed, the skin material 2 is peeled off from the original model 1. In addition, the original model 1
When laminating the FRP resin, it is preferable to apply a mold release agent to the surface of the prototype model 1 in advance, as this makes it easier to perform the work of peeling off the skin material 2.

Next, as shown in FIG. 3, the back side of the skin material 2 is reinforced, and a mold M is manufactured. That is, as shown in detail in FIG. 6, first, a cross-shaped rigid frame 3, which is made by combining rigid materials such as steel vertically and horizontally, is joined to the back surface of the skin material 2 to prevent the skin material 2 from deforming. Improves rigidity and strength. In addition, in the space created between the frame-shaped rigid frames 3, a filler 4 such as plaster is filled and hardened to embed the entire rigid frame 3, and this filler 4 also covers the back surface of the skin material 2. It is reinforcing.

Furthermore, a cooling pipe 5 is buried between the back surface of the skin material 2 and a slight space therebetween. That is, at appropriate locations on the entire surface of the mold M, cooling pipes 5 are embedded inside the filler 4 by penetrating a part of the rigid frame 3, and cooling water or cooling air can be introduced into the cooling pipes 5. The cooling of the molded product, which will be described later, is accelerated.

A pair of upper and lower molds M configured as described above
As shown in Fig. 4, the skin material 2 on the inner side
When the flange portions 20 of the two are aligned and the mold is closed, a mold cavity C corresponding to the outer shape of the original model 1 is formed inside the skin material 2. In addition, in order to reliably fix the mold closed state, the molds M may be fixed to each other by a fastening mechanism such as a bolt.

In this state, a filling nozzle is inserted into the mold cavity C to fill the mold cavity C with expandable thermoplastic resin particles. Therefore, an insertion hole for a filling nozzle is formed in advance in a part of the mold M and the skin material 2.

Next, the heating probe 6 is inserted into the mold cavity C instead of the filling nozzle. Then, a heating medium such as heated steam is ejected from the tip of the heating probe 6 to heat and foam the resin particles in the mold cavity C to fuse and integrate them, so-called probe molding. That is, as shown in FIG. 7, the heating probe 6 is first inserted deep into the mold cavity C, and the heating medium is ejected from the heating probe 6 to heat and fuse the resin particles at that location. The heating probe 6 is gradually pulled out as the particles are fused and hardened, and as the heating probe 6 is pulled out and moved, the resin particles in the entire mold cavity C are heated and fused, thereby manufacturing the molded product P.

The above-mentioned probe molding itself can be performed by a method similar to a conventionally known method, and prior examples of probe molding are disclosed in, for example, Japanese Patent Publication No. 52-32781 or Japanese Utility Model Publication No. 34-4689. .

After heating and fusing the resin particles in the entire mold cavity C as described above, the entire mold M is cooled to cool and harden the molded product P. After that, the mold M is opened, and the molded product P Once removed, the foam molding is complete.

As shown in FIG. 5, the manufactured molded product P has the same external shape as the original model 1, and the inside of the molded product P has a small hole h at the location where the heating probe 6 was inserted. remains.

In addition, if the above-mentioned mold M is closed and each process is performed sequentially from the step of filling the expandable thermoplastic resin particles again, the molded product P can be manufactured repeatedly, and it is not as durable as conventional molds. However, if the number is relatively small, it is fully possible to repeatedly manufacture the molded product P.

Among the foam molding methods explained above, the prototype model 1 only needs to have enough strength to not be deformed or crushed when forming the skin material 2 using FRP resin, and there is no need for a precise wooden mold like in the past. , models made of foam, plaster, etc. can be used satisfactorily. In particular, if the actual molded product P manufactured in the past is used as the prototype model 1, the manufacturing cost will be low, the precision of the external shape will be high, and this will be a practical and suitable implementation.

Next, in the process of forming the skin material 2, it is sufficient to appropriately divide the prototype model 1 and manufacture separate skin materials 2 for each part. The division positions can be changed as appropriate. In addition, by forming a flat flange 20 as shown in the figure at the joint between the plurality of skin materials 2, it is possible to easily form the mold M, and also to facilitate mold matching in the molding process. I can do it accurately. Note that the thickness of the FRP resin laminated as the skin material 2 may be relatively thin, and even for a large molded product P, a thickness of approximately 10 mm is usually sufficient.

In the manufacturing process of the mold M, the rigid frame 3
In addition to steel, structural materials with excellent rigidity and strength, such as various metal materials and wood, can be freely used.The above materials are combined in the form of crosspieces vertically and horizontally over the entire back surface of the skin material 2. What is necessary is just to reinforce it, and the combination pattern of steel materials, the number of steel materials, etc. used can be changed as appropriate other than those shown in the drawings. In addition, as a means of joining the rigid frame 3 to the skin material 2, in addition to using an adhesive, the rigid frame 3 may be brought into contact with the back surface of the skin material 2 before the FRP resin that will become the skin material 2 hardens. For example, the rigid frame 3 can be joined simultaneously with the hardening of the skin material 2.

The filler material 4 that fills the space of the rigid frame 3 can be easily filled and hardened, such as plaster or plaster, and has a certain degree of rigidity, so that it can be molded together with the rigid frame 3. It is preferable to use a material that can improve the strength of the entire M and prevent deformation of the skin material 2. Moreover, especially when embedding the cooling pipe 5 inside the filler 4, a material with good heat conductivity during cooling is desirable.

Note that the cooling pipe 5 is effective for promoting cooling of the molded product P and the mold M after molding, but
It is also possible to perform cooling only by cooling without using the cooling pipe 5. Further, the mold M may be provided with cooling fins.

Next, in the molding process, the expandable thermoplastic resin particles to be filled into the mold cavity C are polystyrene,
Expandable particles made of polyethylene, polypropylene, styrene-ethylene copolymer, and various other thermoplastic resins can be freely used, and are appropriately selected and used depending on the purpose of the molded product P.

By inserting a plurality of heating probes 6 at the same time as appropriate depending on the shape and size of the mold cavity C, the resin particles can be heated quickly and the efficiency of the molding process can be improved. In particular, as shown in FIG. 7, by inserting the heating probe 6 from both ends of the mold cavity C and heating simultaneously from the center to both ends of the mold cavity C, the insertion length of the heating probe 6 can be shortened. , heating efficiency is also good and suitable. Furthermore, the heat fusion of the resin particles is controlled by adjusting the extraction speed of the heating probe 6, the temperature of the heating medium, the injection amount, etc.

<Effects> According to the method of the present invention configured as described above, a mold formed by reinforcing the back surface of the skin material 2 made of FRP resin without using a conventional mold as a mold. M is used. The skin material 2 is formed by laminating and curing the FRP resin directly on the outer surface of the prototype model 1, so it can be formed very easily and efficiently. In addition, it is now possible to form the skin material 2 directly from the actual model without the need to create a wooden mold.
The manufacturing cost of the entire mold M is also much lower than that of a metal mold. Moreover, since the mold is directly taken from the original model 1, the skin material 2, that is, the mold M, can be manufactured with an accurate shape corresponding to the outer shape of the original model 1. Furthermore, in the case of molds, it is technically very difficult to manufacture molds with very large shapes, and the cost is also high, but with the skin material 2 of the present invention, the above-mentioned There are no restrictions at all, and even fairly large products can be manufactured without any problems and at a relatively low cost.

If only a thin skin material 2 is used, it is inferior in rigidity and strength, and there is a risk of deformation due to foaming pressure in the foam molding process. Since the reinforcement is applied, the above deformation can be reliably prevented, and the finishing accuracy of the molded product P is as accurate as that of conventional molds. In addition, regarding the durability of the mold M, if the number of molded products P produced is relatively small, even if the mold M uses the skin material 2 of the present invention, there will be no problem and the durability will be sufficient. It can be used practically.

Next, the mold M formed as described above
After inserting a filling nozzle directly into the mold cavity C from the outside of the mold M to fill the raw material resin particles, the heating probe 6 is further inserted into the mold cavity C to blow out a heating medium such as steam. By performing so-called probe molding, in which the molded product P is produced by heating and fusing resin particles, it is possible to attach the attachment mechanism to the molding machine, the raw material filler, etc., like a conventional mold. No need to install. Therefore, even with the mold M of the present invention, which is somewhat inferior in strength and precision in external shape and difficult to form a complicated attachment mechanism, etc. compared to a mold, it is possible to perform foam molding satisfactorily. It is something.

Furthermore, since complicated equipment such as a molding machine is completely unnecessary and the molding work is easy, there is no longer any restriction on the size of the molded product P due to the capacity of the molding machine, and large molded products P can be formed freely. become.

For example, as a molded product P produced by the method of this invention,
We were able to manufacture core material for surfboards with a length of 4000 mm, width of 600 mm, and thickness of 160 mm.

As stated above, according to the method of this invention,
It is possible to manufacture large molded products P, which was difficult in the past, extremely easily and efficiently, and is extremely effective, especially in the case of molded products P whose production is relatively small, and is suitable for foam molding applications or This can also greatly contribute to expanding demand.

[Brief explanation of drawings]

The figure shows an embodiment of the invention.
5 to 5 are sectional views showing the sequential molding process, FIG. 6 is a perspective view of the main part at the stage of FIG. 4, and FIG. 7 is a schematic plan view. 1...Prototype model, 2...Skin material, 3...Rigid frame, 4...Filling material, 5...Cooling piping, 6...
...heating probe, M...molding mold, P...molded product.

Claims (1)

[Claims] 1. The outer surface of the prototype model is divided into two parts, and FRP resin is laminated separately along the outer surface of each part,
In the process of forming skin materials for a pair of molds, after joining a cross-shaped rigid frame to the back of each skin material, the space between the rigid frames is filled with a filler such as plaster. Step of reinforcing the back side and forming a pair of molds, introducing a filling nozzle from the outside of the mold into the cavity of the mold, and filling the cavity with expandable thermoplastic resin particles from this filling nozzle. After that, a heating probe is inserted into the mold cavity from the outside of the mold, and the resin particles are heated and fused using the heating medium ejected from the heating probe to produce a molded product. A foam molding method characterized by: 2. The foam molding method according to claim 1, wherein cooling piping is buried near the back surface of the skin material in the mold forming step.