JPH0511529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a film-like plastic molded article by a powder slush molding method.

(Prior Art) Conventionally, film-like plastic molded products used as outer skins of vehicle armrests, furniture cushion products, etc. have been manufactured by various methods. Among these manufacturing methods, the powder slush molding method is a method that has been attracting attention in recent years because it can easily produce thin films or films with elaborate patterns, shapes, etc.

As shown in FIG. 3, this method of manufacturing a film-like plastic molded product by the powder slush molding method includes a bucket 12 containing a thermoplastic plastic powder 10, and a heatable mold 14 having a cavity surface 14a. The outline of the process is as follows. First, the mold 14, which has been heated in advance by a heating means 16 such as a heating medium circulation pipe, is placed over the bucket 12 containing the thermoplastic plastic powder 10 with a lid, and the mold 14 and the bucket 12 are placed together with a lid. The thermoplastic powder 10 is moved into the cavity of the mold 14 by rotating it upside down. Thermoplastic powder moved into the cavity 1
0 adheres to the heated cavity surface 14a in a layered manner by coming into contact with the cavity surface 14a. Thereafter, the mold 14 and the bucket 12 are rotated again to return to their original positions, and the surplus thermoplastic powder that was not used for the deposition is stored in the bucket 12. Then, if necessary, the mold 14 is further heated to melt and gel the adhered powder 10 to form a molten film. Subsequently, the mold 14 is cooled, thereby hardening the molten film to fix its shape, and by removing the cured film from the mold, a desired film-like plastic molded article is obtained.

By the way, the bucket 12 is usually larger than the product molding part of the mold 14 so that it can be used in various molds, and the mold cavity surface is also larger than the product molding part to match the bucket. be done. For this reason, in the past, when the thermoplastic powder was inverted, it adhered to the periphery of the molded part of the product on the cavity surface 14a, and unnecessary burrs were formed on the outer periphery of the product, so burr removal work was required after demolding the molded product. As this became necessary, there was a loss of raw materials.

Therefore, in order to solve these problems and produce film-like plastic molded products, the present applicant filed an invention relating to a powder slush molding apparatus in Japanese Patent Application No. 60-286683. As shown in FIG. 4, the powder slush forming apparatus includes a plate-shaped peripheral wall 20 provided in the thermoplastic powder storage portion 18 of the bucket 17 so as to substantially match the outer peripheral shape of the product molding portion a of the mold 22, and A sealing material 24 is provided at the upper end of the peripheral wall 20, and when the mold 22 is placed on the bucket 17, the sealing material 24 is pressed against the cavity surface to seal that part. By manufacturing a film-like plastic molded product using this molding equipment, it is possible to prevent, or mask, thermoplastic plastic powder from adhering to the cavity surface other than the product molded part a, and the above problem can be solved. It was.

(Problem to be Solved by the Invention) However, most of the cavity surface 23 of the mold 22 is a concave curved surface, and depending on the plate-shaped peripheral wall 20 erected on the bucket side, it may touch the cavity surface perpendicularly. There is an intractable problem. Therefore, depending on the shape of the cavity surface (product shape), there is a risk that sealing defects may occur during the production of film-like plastic molded products. In addition, in order to bring the plate-shaped peripheral wall 20 into contact with the cavity surface perpendicularly, it is necessary to provide a plane substantially perpendicular to the peripheral wall 20 on the cavity surface.
If you want to change the position of 0 (change the masking part) or change the shape of the peripheral wall 20, you have to change the shape of the cavity surface, which requires a huge number of man-hours. There is.

This invention solves the problems of the prior art, namely, that depending on the shape of the cavity surface, it may not be possible to completely prevent the formation of a plastic film on unnecessary parts of the cavity surface. The purpose is to solve the problem that it is not easy to mask any part, and furthermore, to provide a manufacturing method that can perform masking more efficiently.

(Means for Solving the Problems) The first invention uses a powder slush molding method in which thermoplastic plastic powder is adhered to the mold cavity surface and the adhered powder is melted to form a film. In a method for manufacturing a film-like plastic molded product, a masking member having a desired shape is brought into contact with and fixed to a cavity surface via a heat insulating material so as to cover a predetermined portion of the cavity surface, and the thermoplastic plastic powder is attached to the cavity surface. It is characterized by melting powder and forming a film.

A second invention is a method for manufacturing a film-like plastic molded product using a powder slush molding method, in which a masking member having a desired shape is placed so as to cover a predetermined portion of a cavity surface, and to leave a space between the masking member and the cavity surface. The thermoplastic powder is adhered to the cavity surface through a heat insulating material, and while the air in the space is circulated with outside air or cold air, the thermoplastic plastic powder is attached to the cavity surface and the adhered powder is melted. and forming a film.

(Operation) First, the first invention will be explained. A first aspect of the invention is to apply a masking member having a desired shape to cover a predetermined portion of the cavity surface, and to contact and fix the masking member to the cavity surface via a heat insulating material, and to apply thermoplastic to the cavity surface using a powder slush molding method. A film-like plastic molded article is produced by depositing powder, melting the deposit, and cooling and hardening the melt. That is, a film is formed by covering a predetermined portion of the cavity surface with a masking member. Therefore, it has the following effects.

The cavity surface is heated in advance to a predetermined temperature by a heating medium flowing through a circulation pipe provided in the mold in order to adhere and melt the thermoplastic powder. However, in the portion where the cavity surface is covered by the masking member, the masking member is in contact with the cavity surface via the heat insulating material, so the heat of the cavity surface is difficult to be transmitted to the masking member, and the temperature of the masking member surface is low. It is maintained below the cavity surface temperature and below the melting temperature of the thermoplastic powder. Furthermore, if a space is provided between the masking member and the cavity surface, the influence of heat radiation from the cavity surface can also be reduced. Therefore, even if thermoplastic powder comes into contact with or accumulates on the masking member by inverting the mold and bucket, the powder will not be heated because the temperature of the surface of the masking member is lower than the melting temperature of the powder. It does not become semi-molten and does not adhere to the masking member.
That is, only the portion of the cavity surface covered by the masking member is free from adhesion of the thermoplastic plastic powder, and the powder is adhered to the other portions. As a result, even if a film is formed on the cavity surface by the subsequent melting and gelling of the thermoplastic plastic powder and cooling and hardening of the melt, the film will not be formed on the portion covered by the masking member. be.

Therefore, by masking (covering) the portions of the cavity surface where the film is not desired to be formed with the masking member, the formation of the film on the outside can be prevented.

In addition, since the masking member is brought into contact with the cavity surface via the heat insulating material and fixed to the mold by the fixing means, the heat insulating material is sandwiched between the masking member and the cavity surface, and the heat insulating material also acts as a sealing material. I will do it. As a result, it is possible to reliably seal between the masking member and the cavity surface.

Furthermore, since the heat insulating material is located between the masking member and the cavity surface and the sealing material acts very well as described above, even if the shape of the cavity surface at the mounting part of the masking member is not flat, the seal between the masking member and the cavity surface can be ensured. can do. Therefore, any part of the cavity surface can be masked without being affected by the shape of the cavity surface, and the masking position can be easily changed without changing the shape of the cavity surface.

On the other hand, the second invention provides a masking member with a space between the masking member and the cavity surface,
As in the first invention, the thermoplastic powder is fixed to a mold, and the thermoplastic powder is adhered to the cavity surface, melted, and a film is formed while circulating the air or cold air in the space.

Therefore, in this second invention, in addition to the effect of the first invention, the masking member is forcibly cooled, so that the masking member is made of thermoplastic powder by heat dissipation from the cavity surface. It is possible to reliably prevent the body from being heated above its melting temperature, and it is possible to more reliably prevent the thermoplastic plastic powder from adhering to the masking member.

(Example) This invention will be explained below based on an example using drawings.

FIG. 1 is a sectional view of a mold 30 and a bucket 32 used when carrying out the first invention.

The mold 30 is usually made of an electroforming mold, has a cavity surface 34 formed on its inner surface, and has a heat medium circulation pipe 36 as a heating means arranged on its outer surface. There are various heating means other than circulating a heat medium, and depending on the means, a circulation pipe may not be necessary.

Further, the cavity surface 34 is larger than the product forming part (the part that will become the product) for reasons such as matching the size of the bucket 32. A masking member 38 is fixed to the mold 30 so as to cover a predetermined portion of the cavity surface 32, that is, a portion to which thermoplastic powder is not desired to adhere.

The masking member 38 is made of a material having high rigidity and a predetermined heat resistance, such as a molded product of fiber reinforced plastic (FRP) or a molded ceramic product, and its shape is approximately the same as a predetermined portion of the cavity surface shape. It has the same flat plate shape or a hollow box shape as in this example, or any other shape that can cover a predetermined portion of the cavity surface. In particular, in order to prevent thermoplastic powder from accumulating on the outer surface of the masking member and to allow it to easily slide off the outer surface, the outer surface shape of the masking member 38 is designed to be free from recesses and relative to the depth of the cavity. and a masking member 38 to form a slope.
It is preferable to make the outer surface as smooth as possible.

The heat insulating material 40 is made of an asbestos board, a rock wool board, etc., and is sandwiched between the masking member 38 and the cavity surface 34. Therefore, the heat insulating material 40 acts not only as a heat insulator but also as a sealing material. Further, as shown in FIG. 2 showing a cross section of a part of an example of a mold used in the second invention, a heat-resistant elastic body 40a such as silicone rubber or fluorine rubber is provided between the heat insulating material 40 and the masking member 38. It's okay. In this way, even if the cavity surface 34 has large irregularities and the sealing action of the heat insulating material 40 alone cannot completely seal between the cavity surface 34 and the masking member 38, the heat-absorbing elastic body 40a can connect the heat insulating material 40 and the masking member 38 and is compressed and deformed, the sealing can be performed completely. Therefore, any part can be masked without being affected by the cavity surface shape.

Further, as means 42 for attaching the masking member 38 to the mold 30, screwing with bolts and nuts, or fixing a clip to the inner surface of the masking member 38 and locking the clip to the mold 30, etc. There is a means of

The masking member fixed to the mold by the fixing means and the cavity surface may be in close contact with each other with a heat insulating material in between, but as shown in FIG.
It is preferable that the masking member 38 and the cavity surface 34 be in contact with each other with a space 39 between them. The reason for this is that by providing the space 39, the influence of heat radiation from the cavity surface 34 can be reduced.

On the other hand, the bucket 32 has an internal housing section 44 for thermoplastic powder, and an external flange section 46 having a shape that matches the mold 30.

Next, an example of manufacturing a film-like plastic molded article according to the first invention will be explained in accordance with the steps.

First, a thermoplastic powder 48 such as vinyl chloride resin powder or polyethylene powder is put into the powder container 44 of the bucket 32 .

Next, the bucket 32 is covered with the mold 30 which has been heated in advance by passing a heating medium such as thermal oil through the circulation pipe 36, and the mold 3 is closed.
0 and the bucket 32 are rotated and placed upside down.

By this inversion, the thermoplastic plastic powder 48 contained in the bucket 32 is transferred to the mold 3.
0 and comes into contact with the cavity surface 34, and is immediately turned into a semi-molten state by the heat of the cavity surface 34 and adheres to the cavity surface 34. At this time,
The thermoplastic powder 48 also contacts the outer surface of the masking member 38, but the heat insulating material 40 prevents heat transfer from the cavity surface 34 to the masking member 38, so that the masking member 38 is lower than the cavity surface temperature. Since the temperature is also lower than the melting temperature of the powder, the contact powder is not heated and becomes a semi-molten state, and does not adhere to the masking member 38. In particular, there is a space 3 between the cavity surface 34 and the masking member 38.
9, heating of the masking member 38 due to heat dissipation from the cavity surface 34 is suppressed, so that the temperature of the masking member 38 can be lowered, and the adhesion of the powder is more reliably achieved. It can be prevented. The powder that has come into contact with the outer surface of the masking member 38 slides down from the outer surface of the masking member 38 due to the slope of the outer surface of the masking member 38 and the smoothness of the outer surface, and does not accumulate on the outer surface of the masking member 38. As a result, for example, if the temperature of the masking member 38 is close to the melting and gelling temperature of the thermoplastic plastic powder 48 and the powder 48 comes into contact with the masking member 38 for a long time, it may become semi-molten and adhere to the masking member 38. Even if there is, such adhesion will not occur.

Thereafter, the mating mold 30 and the bucket 32 are rotated, and the bucket 32 is returned to its original position, ie, the bucket 32 is placed down, and the surplus thermoplastic powder not used for the deposition is stored in the storage part 44 of the bucket.

In this way, the thermoplastic plastic powder adhering to the cavity surface 34 except for the portion covered by the masking member 38 is melted and gelled by continuing to heat the mold 30, if necessary, to form a molten film. Form.

Thereafter, the mold 30 is cooled to harden the molten film, and the cured film is removed from the mold to obtain a film-like plastic molded product having a desired shape.

The obtained molded product has no film formed on the portion covered by the masking member 38. Therefore, by providing the masking member 38 in a part of the mold other than the product forming part, a product without burrs can be obtained.

Next, the production of a film-like plastic molded article according to the second invention will be explained.

FIG. 2 is a sectional view of a main part of an example of a mold 30a used in the second invention. The masking member 38 having the desired shape is attached to the cavity surface 34 of the mold 30a.
A space 39 is formed between the insulation material 40 and the insulation material 40.
It is fixed to a predetermined portion of the cavity surface by fixing means 42 via the heat-resistant elastic material 40a. Cavity surface 3 covered with masking member 38
A hole 49 is formed in a predetermined portion of the hole 4a.
9 is connected to an air pressure hose 50 for blowing cold air or outside air into the space 39.

The second invention is to manufacture a film-like plastic molded product by a powder slush molding method using this mold 30a and the bucket 32, and the content thereof overlaps with the invention in the first invention. Since there are many parts, the second invention will be explained by simplifying the overlapping parts.

First, pour thermoplastic powder into a bucket.
The bucket 32 is covered with the heated mold 30a. At this time, in the space 39 between the masking member 38 and the cavity surface 34a,
Cold air or outside air is press-fitted from the air press-fitting hose 50, and the air in the space 39 is circulated together with the cold air or outside air. This cools the masking member 38 and ensures that it remains below the melting temperature of the thermoplastic powder at a lower temperature than the first invention. Further, if a small hole is provided in the mold 30a around the hole 49 for connecting the hose 50, the air in the space 39 can be circulated better.

Next, as in the first invention, the mold and bucket are rotated, turned upside down, and further rotated and returned to their original positions, thereby adhering the thermoplastic plastic powder to the cavity surface. At this time, the masking member 38 is cooled by the circulation of the air in the space 39 with outside air or cold air, and the temperature is lower than the cavity surface temperature and lower than the melting temperature of the powder. , masking member 38
Thermoplastic powder will not adhere to the material. Therefore, on the cavity surface, only the portion covered by the masking member 38 is free from adhesion of thermoplastic plastic powder.

As described before and after, the adhering powder is melted and gelled to form a molten film, the mold is then cooled, the molten film on the cavity surface is made into a hardened film, and the film is removed from the mold to form the desired film shape. Obtain plastic molded products. The molded product does not have a film formed on the portion where the cavity surface is covered by the masking member.

(Effects of the Invention) The first invention is such that when manufacturing a film-like plastic molded product by a powder slush molding method, a masking member having a desired shape is used to cover a predetermined portion of the cavity surface via a heat insulating material. By forming a film by abutting and fixing, we were able to obtain the following effects.

That is, by covering with a masking member, it was possible to prevent the thermoplastic plastic powder from adhering to a predetermined part of the opening surface and the masking member, and to prevent the formation of a film on the part (masking). It is. Therefore, by providing a masking member to cover a predetermined portion of the cavity surface where a film is not desired to be formed, it has become possible to obtain a film-like plastic molded product without unnecessary burrs.

Furthermore, it has become possible to reliably mask any part of the cavity surface without being affected by the shape of the cavity surface.

On the other hand, the second invention provides that when manufacturing a film-like plastic molded product by a powder slush molding method, a masking member having a desired shape is inserted into the cavity through a heat insulating material so as to form a space between the masking member and the cavity surface. Because the film was formed by adhering to the surface and circulating the air in the space with outside air or cold air, the following effects could be obtained.

That is, since the masking member can be kept at a lower temperature more reliably, it is possible to completely prevent thermoplastic powder from adhering to the masking member, and masking can now be performed more reliably.

Furthermore, the effect of the first invention, which is that any part can be reliably masked without being affected by the cavity surface shape, can be achieved without impairing it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold and bucket used in the first invention, and FIG. 2 is a sectional view of a part of the mold used in the second invention. Further, FIG. 3 is a sectional view of an example of a mold and bucket used in the conventional manufacturing method, and FIG. 4 is a sectional view of a conventional powder slush forming apparatus. 30, 30a...Mold, 38...Masking member, 39...Space, 40...Insulating material, 40a...
Heat-resistant elastic material.

Claims (1)

[Scope of Claims] 1. A method for producing a film-like plastic molded product by a powder slush molding method in which thermoplastic plastic powder is adhered to the mold cavity surface and the adhered powder is melted to form a film. In this step, a masking member having a desired shape is brought into contact with and fixed to a predetermined part of the cavity surface via a heat insulating material, and the thermoplastic powder is adhered to the masking part without forming a film on the masking part. A method for producing a film-like plastic molded product, which comprises melting and forming a film. 2. The method for manufacturing a film-like plastic molded product according to claim 1, wherein a space is provided between the cavity surface and the masking member. 3. In a method of manufacturing a film-like plastic molded product by a powder slush molding method in which thermoplastic plastic powder is adhered to the mold cavity surface and the adhered powder is melted to form a film, masking of a desired shape is performed. The member is fixed in contact with the cavity surface via a heat insulating material so as to cover a predetermined portion of the cavity surface and to form a space between the member and the cavity surface, and the air in the space is replaced with outside air or cold air. 1. A method for producing a film-like plastic molded article, which comprises adhering thermoplastic plastic powder, melting the adhering powder, and forming a film while circulating the following steps.