JP2006281707A - Molding method of resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a resin molded product of good quality having no borderline called as the so-called shock line when a heated and softened thermoplastic resin sheet is brought into contact with a mold to be molded like stamping molding or vacuum forming. <P>SOLUTION: When the heated and softened thermoplastic resin sheet W is brought into contact with a first mold 1 to be molded, the protruded parts A and B, with which the sheet W comes into contact precedently, are coated with an epoxy resin of which the heat conductivity is lower than that of the first mold 1 to form low heat conductivity layers (x) so as to make it hard to transmit the heat of the first contact part of the sheet W to the first mold 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molding method in which a heat-softened resin sheet is brought into contact with a mold and molded into a predetermined shape.

Conventionally, for example, in stamping molding or vacuum molding, a thermoplastic resin sheet is heated and softened and brought into contact with the molding surface of the mold, and the sheet is pressed from the opposite direction of the molding surface side, or a vacuum is applied to the molding surface side. Or the like, and the sheet is formed in close contact with the molding surface.
At this time, in the stage where the sheet is brought into contact with the molding surface of the mold, the portion where the sheet first contacts the molding surface is deprived of heat from the sheet by the mold, so that solidification proceeds compared to the surrounding portion. Difficult to deform locally. For this reason, the thickness of the part that contacts the mold in the initial stage is thick as it is at the initial thickness, and the thickness of the part that is stretched and then molded is thin, and the sheet is formed with wrinkles or the like. In this case, the depth of the first contact portion is deep and the depth of the portion to be molded later is also shallow, so that a so-called shock line boundary is generated.

In order to prevent such problems, for example, in an apparatus for stamping and molding a thermoplastic resin sheet, a hot air outlet is provided at a protruding portion where the sheet contacts the molding surface of the mold, and the sheet is placed on the mold. At this time, a technique for preventing the sheet from solidifying locally by supplying hot air is known (for example, see Patent Document 1).
Japanese Patent Publication No. 5-50374

  However, the above-described technique requires the improvement of the mold structure, has a complicated structure, and increases the running cost.

  Therefore, the present invention provides a good quality with no boundary line called a so-called shock line when molding a heat-softened thermoplastic resin sheet in contact with a mold, such as stamping molding or vacuum molding. The purpose is to obtain goods.

  In order to achieve the above object, the present invention provides a method for molding a resin molded product in which a heat-softened thermoplastic resin sheet is brought into contact with a mold and molded into a predetermined shape, and the thermoplastic resin sheet is brought into contact with the mold. In this case, at least a part of the protruding portion of the molding surface of the mold with which the sheet comes into contact first is covered and molded with a member having a thermal conductivity lower than that of the mold.

In this way, if a molded product is formed by covering the protruding portion of the molding surface of the mold with which the sheet comes into contact first with a member having low thermal conductivity, the thermoplastic resin sheet that first contacts the mold The temperature of the contact portion is slowed down by the metal mold and decreases, and local premature solidification is prevented.
Here, as a member having low thermal conductivity, it is preferable to obtain adhesion to a mold. For example, if a resin, a paint, or the like is applied or coated, it is easy to work and is suitable.

When the heat-softened thermoplastic resin sheet is brought into contact with the mold and molded, the molding surface of the mold that comes into contact with the sheet in advance is coated with a member having low thermal conductivity to form the initial stage. Local solidification of the abutting portion is prevented, generation of a boundary line called a so-called shock line can be suppressed, and molding quality is improved.
In this case, it is possible to deal with the cost cheaply and easily compared with the case where a mold for blowing hot air is provided.

Embodiments of the present invention will be described with reference to the accompanying drawings.
Here, FIG. 1 is an explanatory diagram showing an example of a molding die to which the molding method according to the present invention is applied, FIG. 2 is an explanatory diagram of the present molding method, FIG. 3 is an explanatory diagram of a conventional molding method, and FIG. It is explanatory drawing of the shock line produced in the molded article shape | molded by the method.

  The method for molding a resin molded article according to the present invention is a vacuum in which vacuum forming is performed by bringing a heat-softened thermoplastic resin sheet into contact with a molding surface of a mold and vacuuming from a vacuum hole provided in the mold. In the molding method, it is possible to prevent the occurrence of a so-called boundary line called a shock line. Before explaining the molding method of the present invention, the conventional molding method and its defects are shown in FIGS. This will be explained based on this.

  As shown in FIG. 3, in vacuum forming, as shown in FIG. 3A, the periphery of the heat-softened thermoplastic resin sheet W is held by the gripping frame 52, and then the gripping frame 52 is lowered to move the sheet W. While covering the upper surface of the molding surface of the mold 51 and evacuating from a number of vacuum holes opened in the molding surface of the mold 51, the sheet W is formed in close contact with the molding surface. In the stage of covering the molding surface of the mold 51 with the sheet W, as shown in (b), the mold 51 is deprived of heat at the sheet portions Wa and Wb that first contact the protruding portions A and B of the mold 51. Since it is cooled and solidified locally and then becomes smaller than the elongation of the sheet portion Wc in contact with the mold 51, a boundary line s called a shock line is generated at the boundary part.

  When the sheet W is decorated with a texture pattern or a satin finish, the depth of the texture or the like becomes different at the boundary line s, which reduces the appearance.

  Here, when the molded product W is a skin material of the instrument panel of the vehicle, as shown in FIG. 4, the boundary line s of the shock line is generated in the vicinity of the protruding portion. Since it is a place that is easily noticeable, it is not preferable in terms of quality.

  Therefore, in the present invention, the protrusion of the mold forming surface with which the sheet W comes into contact first is coated with a member having a thermal conductivity lower than the thermal conductivity of the mold, specifically, a resin or paint. The gist is to do.

  That is, as shown in FIG. 1, the molding method according to the present invention is applied to vacuum molding using a vacuum molding die, and the vacuum molding die includes a first molding die 1 as a die having a molding surface, and heating. A gripping frame 3 that holds the periphery of the thermoplastic resin sheet W to be softened and a second mold 2 that presses a predetermined portion of the sheet W from above are provided.

  And the low heat conductive layer x with low heat conductivity, such as resin and paint, is formed on the top surface of the projecting portions A and B where the sheet W is first brought into contact by lowering the sheet W of the molding surface of the first mold 1. Is forming.

Then, by forming the low heat conductive layer x on the top surfaces of the protruding portions A and B, even if the sheet W first comes into contact, it becomes difficult for the heat of the same portion to be transmitted to the first mold 1, Therefore, it is possible to maintain the same degree of deformation as that of the peripheral portion.
Here, examples will be described.

  The first mold 1 is an aluminum mold, the second mold has an iron frame structure, and the top surface of the protruding portions A and B of the first mold 1 has an epoxy resin thickness of about 0.05 mm. Coated. In this embodiment, this coating is applied by brush or the like, but it may be sprayed or the like, or other methods may be used.

  On the other hand, as the thermoplastic resin sheet W, a TPO sheet or PP sheet decorated with an embossed pattern such as a concavo-convex pattern, a leather pattern, or a geometric pattern is used, and a temperature at which the sheet W can be deformed. While being heated to about 180 ° C. and held by the gripping frame 3, the mold temperature of the first mold 1 is set to about 70 ° C. at which the sheet W can be solidified, and as shown in FIG. Is lowered and the sheet W is placed on the molding surface of the first mold 1, and at the same time, the second mold 2 is lowered to press a predetermined portion of the sheet W, and a vacuum is drawn as shown in FIG. Then, it was brought into close contact with the molding surface and cooled and solidified.

The molded product W molded in such a manner was neatly molded without causing a boundary line called a shock line and without causing a difference in the depth of a texture pattern or the like.
As a result, the effectiveness of the present invention was confirmed.

In the present embodiment, an epoxy resin is used as the resin of the low thermal conductive layer x for the first mold 1 made of aluminum. This is because the epoxy resin is approximately 1 / the thermal conductivity of aluminum. The combination of an aluminum mold and an epoxy resin is as low as about 1000, and the epoxy resin is excellent in adhesion to metal, and the epoxy resin is excellent in heat resistance, toughness, corrosion resistance, etc. It is.
Of course, resins other than epoxy resins can be used as long as the heat insulating property can be lowered.
Moreover, it is applicable also to resin molding other than vacuum forming.

  When the heat-softened thermoplastic resin sheet is brought into contact with the molding surface of the mold and molded, the protruding portion of the molding surface that comes into contact with the sheet is covered with a member having low thermal conductivity and molded. In addition, appearance defects such as shock lines are suppressed, and the procedure is simple and inexpensive.

Explanatory drawing which shows an example of the shaping | molding die with which the shaping | molding method concerning this invention is applied Illustration of this molding method Explanatory drawing of conventional molding method Explanatory drawing of shock line generated in a molded product molded by the conventional method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st shaping | molding die, W ... Thermoplastic resin sheet, x ... Low heat conductive layer.

Claims (1)

A method of molding a resin molded product in which a heat-softened thermoplastic resin sheet is brought into contact with a mold and molded into a predetermined shape, wherein the sheet precedes when the thermoplastic resin sheet is brought into contact with the mold. A molding method for a resin molded product, comprising: molding at least a part of a protruding portion of a molding surface of a mold that comes into contact with a member having a thermal conductivity lower than that of the mold.