JP2007182035A - Manufacturing method of vacuum-formed product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a vacuum-formed product, transferring a fine uneven shape of embossing even by vacuum forming. <P>SOLUTION: When a thermoplastic resin sheet 12 is vacuum drawn with a mold 1, because the mold 1 is cooled while the vacuum forming is under way, the fine uneven embossed shape 10 of the thermoplastic resin sheet 12, which has been transferred in correspondence to the cavity surface 3 of the mold 1 at the initial time of the vacuum forming, can be stabilized as it is. Accordingly, it is possible to transfer the fine uneven embossed shape 10 even with vacuum forming not requiring large-scale equipment. It is preferable that the heating temperature of the mold 1 is 100-140°C and the cooling temperature is 60-80°C. Upon conducting the vacuum forming of the thermoplastic sheet 12 with the mold 1, if compressed air of 0.05-0.5 MPa is applied from a plug assist 2, the transfer is improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a vacuum molded product having a fine uneven-drawing shape on its surface.

In order to enhance the texture, the surface of a resin molded product used for an automobile interior material or the like is provided with a fine uneven drawing shape such as high-quality suede tone, natural leather tone, and fine pore tone. Such a fine concave-convex drawn shape is formed by applying sufficient temperature and pressure by, for example, injection molding of a thermoplastic resin (see, for example, Patent Document 1).
JP 2004-322392A

  However, since injection molding requires a large-scale facility and has a large cost burden, it has been studied whether or not a fine uneven-drawing shape can be formed by vacuum forming that requires relatively simple facilities. In vacuum forming, even if the surface of the resin sheet is temporarily shaped into a shape that corresponds to the fine concave and convex shape of the mold in the initial stage of vacuum suction, the fine concave and convex shape formed by the restoring force of the resin is the mold. There is a risk of collapse.

  The present invention has been made by paying attention to such a conventional technique, and provides a method for manufacturing a vacuum molded product capable of transferring a fine uneven drawing shape even by vacuum forming.

  According to the first aspect of the present invention, a fine concave / convex drawn shape that can be transferred by vacuum forming is formed on the cavity surface of a vacuum forming mold, and the thermoplastic resin sheet is heated at least from the surface side at a temperature not lower than the softening point. The heated thermoplastic resin sheet is vacuum-sucked by a mold and vacuum-molded, and the mold is cooled while being vacuum-sucked, and the fine uneven-constricted drawn shape is transferred to the surface of the thermoplastic resin sheet. To do.

  According to the first aspect of the present invention, when the thermoplastic resin sheet is vacuum sucked by the mold, the mold is cooled while being vacuum formed. Further, the fine uneven drawing shape of the thermoplastic resin sheet can be stabilized as it is. Accordingly, it is possible to transfer a fine uneven-shaped drawing even in vacuum forming that does not require a large-scale facility.

  The object of the present invention is to provide a manufacturing method of a vacuum molded product capable of transferring a fine unevenness drawn shape even in vacuum forming, and to provide a fine uneven drawn shape capable of being transferred by vacuum forming to a cavity surface of a vacuum forming mold. The thermoplastic resin sheet is heated at least from the surface side at a temperature equal to or higher than the softening point, and the heated thermoplastic resin sheet is vacuum-sucked by a mold and vacuum-molded. This was realized by cooling and transferring the fine irregularities drawn shape onto the surface of the thermoplastic resin sheet. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1-8 is a figure which shows one Example of this invention. The structure of the mold 1 used in this embodiment will be described with reference to FIGS. The mold 1 is also used in combination with a core-type plug assist 2.

  The mold 1 is an electroforming mold in which a cavity surface 3 on the surface is formed by an electroformed layer 4. On the cavity surface 3, a fine uneven diaphragm shape 10 is formed. The electroformed layer 4 is easy to form a fine irregularity narrowed shape 10 on the cavity surface 3 and is excellent in terms of durability. A vacuum suction hole (not shown) is formed on the entire cavity surface 3. The diameter of the vacuum suction hole is preferably 100 μm or less, although it depends on the size of the fine uneven diaphragm shape 10. If it is 100 μm or less, transfer of the vacuum suction hole itself can be prevented.

  A plurality of hot pipes 5 and cold pipes 6 are alternately provided on the back surface of the electroformed layer 4. A warm fluid can flow through the warm pipe 5 and a cold fluid can flow through the cold pipe 6. The warm pipe 5 and the cold pipe 6 are respectively connected to the back surface of the electroformed layer 4 by brazing 7. It is necessary to set the pitch of the hot pipe 5 and the cold pipe 6 as finely as possible so that the temperature does not easily vary. The hot pipe 5 and the cold pipe 6 are surrounded by a heat insulating material 8, and the electroformed layer 4 and the heat insulating material 8 are held by a backing material 9.

  Next, a method for manufacturing a resin-made vacuum molded product 11 to which the fine concave and convex diaphragm shape 10 is transferred using the mold 1 will be described.

  First, as shown in the molding cycle of FIG. 7, in step 1, a thermoplastic resin sheet (TPO) 12 serving as an automobile interior material is set while being held by a clamp 13, and heating of the mold 1 is started. The electroforming layer 4 of the mold 1 is heated by flowing a warm fluid through the warm pipe 5.

  Next, in Step 2, the thermoplastic resin sheet 12 is heated to 190 ° C. from the upper and lower surfaces by the heater 14. Heating only from the front side may be used, but temperature variation is less likely to occur when heating from both sides. The thermoplastic resin sheet 12 needs to be heated to the softening point or higher. In the case of TPO, the transferability can be improved by heating to 160 to 210 ° C. (preferably 170 to 200 ° C.). As shown in FIG. 8, the heating of the mold 1 was tested at eight temperatures from 150 ° C. to 70 ° C.

  Next, in step 3, when the mold 1 reaches a predetermined temperature, the plug assist 2 is lowered and the thermoplastic resin sheet 12 is pressed against the cavity surface 3 of the mold 1.

  Next, in Step 4, a pressure of 0.2 MPa (preferably 0.05 MPa to 0.5 MPa) is applied from the plug assist 2 and vacuum suction is performed from the cavity surface 3 with a delay of about 0.1 second. Although there is no need for compressed air from the plug assist 2, the presence of the air improves transferability.

  Next, in step 5, the compressed air is stopped, the supply of the hot fluid to the hot pipe 5 is stopped while maintaining the vacuum suction, and the cold fluid is circulated through the cold pipe 6 instead. Cooling. Cooling is performed in a short time until the electroformed layer 4 of the mold 1 reaches 70 ° C. By cooling in a short time, it is possible to stabilize the shape of the fine concavo-convex drawn shape 10 transferred to the molded thermoplastic resin sheet 12 and to facilitate release from the mold 1.

  Next, in Step 6, since the cooling of the mold 1 is maintained, the vacuum is released to atmospheric pressure, the plug assist 2 is raised, and the vacuum molded product 11 is removed from the mold. When the cooling temperature of the mold 1 is extremely lowered, there arises a problem that the molding cycle time is extended and the productivity is lowered, and therefore, 60 ° C. to 80 ° C. is preferable. Further, if the mold release is performed at a high temperature, there arises a problem that the vacuum molded product 11 is plastically deformed at the time of mold release or the dimensional stability of the product is lacking.

  The shape transferability of the eight types of samples (Nos. 1 to 8) obtained for each heating temperature of the mold 1 and the transferability of the fine irregularities narrowed shape 10 were evaluated and shown in FIG. "Skin" indicates the thermoplastic resin sheet 12).

  Sample No. Those of 2 to 5 were good in both shape transfer and squeeze transfer. Accordingly, even the fine portions of the fine concave and convex narrow shape 10 were reliably transferred to the surface of the vacuum molded product 11. In this way, the fine irregularities of the fine irregularity-constricted shape 10 could be reliably transferred because the mold 1 was cooled while the thermoplastic resin sheet 12 was vacuum-formed, and the fine irregularities transferred corresponding to the cavity surface 3 This is because the aperture shape 10 can be stabilized as it is.

  Sample No. 1 where the temperature of the mold 1 is high. No. 1 had an inferior R shape at the bent portion in terms of shape transfer. Further, in terms of the drawing transfer property, an air pool is likely to occur in the portion that has previously contacted the cavity surface 3, and the appearance is poor.

  Sample No. 1 where the temperature of the mold 1 is low. In 6-8, it was not reliably transferred to the fine portion of the fine uneven diaphragm shape 10. In Sample 8, the R shape of the bent portion was slightly poor in terms of shape transfer. From the above, in the case of the thermoplastic resin sheet (TPO) 12, it can be said that the heating temperature of the mold 1 is preferably 100 to 140 ° C.

  In the above description, an example in which the mold 1 is provided with the warm pipe 5 and the cold pipe 6 and the mold 1 is heated and cooled by flowing the warm fluid and the cold fluid in the mold 1 is shown. The heating and cooling of the mold 1 may be selectively performed by supplying a warm fluid to all the pipes or by supplying a cold fluid by switching valves or the like. Further, the present invention is not limited to automobile interior parts, and can be applied to any vacuum-formed product having a fine uneven drawn shape.

Sectional drawing which shows the metal mold | die and plug assist which concern on one Embodiment of this invention. FIG. 2 is an enlarged sectional view showing a DA part indicated by an arrow in FIG. 1. Sectional drawing which shows the heating state of a thermoplastic resin sheet. Sectional drawing which shows the state just before vacuum-sucking a mold thermoplastic resin sheet. Sectional drawing which shows a vacuum formed product. The expanded sectional view which shows the arrow DB part in FIG. The figure which showed the shaping | molding cycle in the table | surface. The figure which showed the molding conditions and the molding result in a table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold 2 Plug assist 3 Cavity surface 4 Electroformed layer 5 Warm piping 6 Cold piping 10 Fine uneven | corrugated narrow shape 11 Vacuum molded article 12 Thermoplastic resin sheet

Claims (1)

Forming a fine concave and convex constricted shape (10) that can be transferred by vacuum forming on the cavity surface (3) of the vacuum forming mold (1),
The thermoplastic resin sheet (12) is heated at least from the surface side at a temperature equal to or higher than the softening point,
The heated thermoplastic resin sheet (12) is vacuum-sucked by the mold (1) and vacuum-molded, and the mold (1) is cooled while vacuum-sucking,
A method for producing a vacuum-molded product, comprising transferring the fine irregularities narrowed shape (10) onto the surface of the thermoplastic resin sheet (12).

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