JP2000301554A - Method for molding tpo powder slush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform powder slush molding of a TPO (thermoplastic elastomer) molded article without generating pinholes and to improve mold release property of the TPO molded article after molding. SOLUTION: A mold 1 with venting holes 7 is heated. A TPO powder is brought into contact with a molding face 2 by rotating the mold 1 to form a TPO molten film 23 and the TPO molten film is sucked on the molding face 2 by making the back face side of the mold 1 vacuum to eliminate gaps 25 and to remove air 24 included in the TPO molten film by suction. The TPO molten film 23 is solidified by cooling the mold 1 to obtain a TPO skin molded article. The TPO skin molded article is air-pressed by pressurizing the back face side of the mold 1 to peel it off from the molding face 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a powder slush molding method using a plastic / olefin (ie, a polyolefin-based thermoplastic elastomer) powder.

[0002]

2. Description of the Related Art Conventionally, for example, instrument panels, glove boxes, consoles, lower covers,
When the skin of the interior of a biller or door is formed by a powder slush molding method, a powder of PVC (polyvinyl chloride resin) or TPU (thermoplastic urethane, that is, a polyurethane thermoplastic elastomer) is commonly used. I was In that case, an electroforming mold has been generally used for the mold.

[0003] In recent years, global environmental problems have been highlighted. In particular, PVC tends not to be used in the production of automobile parts in the near future as a material having a problem on the global environment. Therefore, olefin-based synthetic resins or elastomers, which can be recycled, can be reduced in weight, and cause little problem even when incinerated, have become the mainstream of materials for automobile parts. In particular, when the skin of the component such as the instrument panel is formed by the powder slush molding method, it is clear that TPO powder will be the mainstream of the material in the future.

[0004]

However, when TPO powder is used and powder slush molding is performed by the same method using the same electroforming mold as before, the following two points (1) and (2) are found. A source of difficulty and poor molding,
Practical application was difficult because the yield deteriorated.

(1) A gas pool phenomenon called a pinhole is apt to occur in each part (particularly, a convex corner) of a molded leather-like TPO molded article, and the molded article is likely to be defective.

FIG. 8 shows the mechanism by which a pinhole is formed in the flat portion of the TPO molded product. The flat portion of the mold 51 heated as shown in FIG.
When the PO powder 60 is put on the TPO powder 60, unlike PVC or TPU, which melts uniformly, a part of the TPO powder 60 is melted earlier because there is unevenness in the way of melting (melted portion 61). Then, as shown in (c) and (d), the melted portion 61 becomes the semi-melted portion 6.
When the semi-molten portion 62 melts with a delay, the air contained between the powders is confined as a pinhole 63 as shown in FIG.

FIG. 9 shows a mechanism in which a pinhole is formed at a convex corner portion of a TPO molded product.
The concave corner 52 of the mold 51 heated as shown in FIG.
When the TPO powder 60 enters (particularly where the radius is as small as about 1 mm) as shown in (b), the TPO powder 60 has a specific gravity (about 0.9) higher than that of PVC powder (about 1.25). Due to the small inertia, the gap 64 may be formed without clogging the corner of the concave corner 52. Once the gap 64 is thus formed, (c)
The melting of the TPO powder 60 proceeds as shown in FIG.
Even if 1 is formed, the gap 64 is not closed again and remains as the pinhole 63 as shown in FIG.

(2) When the skin-like TPO molded product obtained by powder slush molding is released from the molding die, the adhesion of the TPO molded product to the molding die is significantly larger than that of a conventional PVC molded product. Since it is very hard to peel off, it takes a lot of trouble and time to release the mold. Also, if the TPO molded product that does not come off is forcibly pulled and peeled off,
The molded product is stretched and deformed, resulting in defective dimensions, and the TPO molded product undergoes a whitening phenomenon (a phenomenon in which the surface color becomes white), resulting in poor appearance.

[0009] These elongation and whitening phenomena are treated by annealing in a PVC molded product (for example, 90 ° C to 1 ° C).
Heating with hot water of 00 ° C or heating for several minutes in an open state) can restore the original shape (return to the original shape of the mold, eliminate the whitening phenomenon).
In the case of O-molded products, such annealing treatment does not pass at all and does not return to the original state.

Further, when the TPO molded product is peeled off from the mold, if it is temporarily stopped and then restarted, glossy unevenness occurs at the point where the TPO is stopped, so it is necessary to continuously peel off without stopping midway. is there. Therefore, large TPO
It is difficult for one worker to release the molded product, and it is necessary to perform the work by a plurality of workers. For example, a release operation of a TPO skin having a size of an instrument panel class requires 3 workers.
About two workers were required.

Therefore, an object of the present invention is to provide a TPO molded product that can be powder slush molded without generating pinholes, and that the molded TPO molded product can be easily and quickly formed without any trouble from a molding die. It is an object of the present invention to provide a TPO powder slush molding method which can be released in time and can prevent elongation and whitening.

[0012]

In order to solve the above-mentioned problems, a TPO powder slush molding method according to the present invention comprises a step of heating a mold having air permeability, and a step of rotating the mold by rotating the mold. The TPO powder is brought into contact with the molding surface of the mold to form a TPO molten film, and the pressure on the back side of the mold is reduced to suck the TPO molten film to the molding surface to eliminate gaps and to suck air contained in the TPO molten film. Removing the TPO, cooling the mold to cure the TPO melt film to form a TPO molded article, and pressing the back side of the mold to evacuate the TPO molded article and peel it off the molding surface And

[0013] In the step of peeling the TPO molded product from the molding surface, the TPO molded product peeled from the molding surface is supported by a receiving surface which is one size smaller than the molding surface provided close to the molding surface. Is preferred.

Further, in the step of peeling the TPO molded product from the molding surface, it is preferable that a part of the TPO molded product is peeled off from the molding surface by an ejector before the compressed air. This is because a space is formed between a part thereof and the molding surface, and the TPO molded product can be easily and smoothly peeled from the space at the time of compressed air. Examples of the ejector include an ejector pin provided on the back side of the molding die and capable of protruding toward the molding surface, and an actuator including a fluid pressure cylinder for driving the ejector pin, an electromagnetic solenoid, and an actuator such as a shape memory alloy. it can. In the case where the receiving surface is provided, an ejector pin which can protrude from a part of the TPO molded product and can be adsorbed and pulled on the receiving surface side, and an actuator such as a fluid pressure cylinder or an electromagnetic solenoid for driving the ejector pin The following can also be adopted.

The "mold having air permeability" is not limited to a specific one, and the following molds (A) to (E) can be exemplified.

(A) As disclosed in Japanese Patent Publication No. 14434/1990, a conductive layer is provided on the surface of a mandrel, and a large number of minute nonconductive portions are provided on the surface of the conductive layer.
By performing electroforming on the surface of the mandrel, a mold main body is formed, and at the beginning of the electroforming, a minute non-electrodeposited portion is generated in the non-conductive portion. A molding die manufactured by forming a large number of ventilation holes in a mold body by penetrating by growing a part. This mold is
Although there may be a vent having an inner diameter of 100 μm or more, the vent can be manufactured at low cost.

(A) As disclosed in Japanese Patent Publication No. 5-39698, a conductive layer having no minute nonconductive portion is provided on the surface of the mandrel, and the conductive layer is substantially free from a surfactant. By performing electroforming on the surface of the mandrel, the mold body is formed, and a small non-electrodeposited portion is generated on the surface of the conductive layer in the early stage of the electroforming, and the non-electrodeposition is performed as the electroforming proceeds. A mold manufactured by forming a vent hole in a mold body by penetrating by growing a part.

(C) As disclosed in Japanese Patent Application Laid-Open No. 9-249987, a step of preparing a matrix having a conductive surface and an electroforming solution containing a surfactant substantially added are:
A first electroforming step of forming an electroformed shell surface layer having no holes by electroforming the conductive surface of the matrix, and removing the matrix and the electroformed shell surface layer from an electroforming solution; In the step of processing a small straight hole whose inner diameter is substantially constant in the hole length direction in the casting shell surface layer, and in an electroforming solution that does not substantially add a surfactant,
By performing electroforming on the back surface of the electroformed shell surface layer, at the same time as forming the electroformed shell back layer, a non-electrodeposited portion is generated in the opening of the fine straight hole at the beginning of the electroforming, and the electroforming is performed. Forming a non-electrodeposited portion as the process proceeds, thereby forming a large-diameter hole having a larger inner diameter toward the rear surface side in the electroformed shell rear surface layer. Although this mold slightly increases the cost, the inner diameter of the vent hole (fine straight hole) opened in the molding surface can be controlled to 100 μm or less.

(D) A gas-permeable porous mold produced by spraying molten metal droplets. Although this mold is not high in durability, it can be manufactured at low cost, so that it is suitable for small lot molding.

(E) A molding die manufactured by forming a ventilation hole in a molding die having no air permeability by machining (e.g., drilling) or laser processing.

In the above-mentioned molding die, the inner diameter of the vent hole opened on the molding surface is preferably as small as possible in order to keep the trace of the vent hole in the TPO molten film at the time of depressurization / suction. In order to reduce airflow resistance during pressurization and pressurization and perform strong suction and pressurization, it is preferable that the pressure is as large as possible.

The range of the inner diameter satisfying these two objectives in a well-balanced manner is 10 to 200 μm, and more preferably 30 to 1 μm.
00 μm. Further, in order to sufficiently satisfy both of these objects, it is preferable to intentionally change the inner diameter according to the portion of the mold. For example, the inside diameter is reduced to about 10 to 100 μm at a part where appearance is a problem (for example, a part that is easily visible or a part having a grain pattern), and a part where the appearance is not a problem (for example, a part that is hard to see or In areas where there is no grain pattern or where cutting is performed after molding, etc.)
For example, it may be increased to about 00 to 200 μm.

The method of heating the mold is not particularly limited, and the following methods (f) to (h) can be exemplified.

(F) A method in which the mold is heated from a remote place by a burner flame, radiant heat of an electric heater, or the like. In this method, the accuracy of the heating temperature control is not high, but the equipment cost is low.

(G) A method in which heated oil is supplied to a temperature control tube connected to the back surface of a mold and heated. Although this method requires equipment costs, it can rapidly and uniformly heat the mold, and has high accuracy of heating temperature control. The mode of connection of the temperature control tubes is not particularly limited, and may be, for example, a connection using a silver brazing, but a fixing structure disclosed in Japanese Patent Application Laid-Open No. 7-227851 is preferable. That is, the temperature control tube is disposed so as to abut on the back surface of the mold body, and a thin body having a large number of through holes and having conductivity on the surface is placed on the temperature control tube from the back surface side, and the mold body is covered with the thin body. An electroformed coating is electroformed on the back surface of the mold body, the temperature control tube, and the thin body, and the temperature control tube is connected to the back surface of the mold body through the thin body and the electroformed coating portion. An embodiment in which the surfaces are bonded to each other is preferable.

(G) A method of heating by supplying power to an electric heater coupled to the back surface of the mold body. Although this method requires equipment costs, it can rapidly and uniformly heat the mold, and has high accuracy of heating temperature control.

The method of cooling the mold is not particularly limited, and the following methods (g) to (g) can be exemplified. (G) A method of cooling the mold by applying water or the like. (G) A method of supplying cooled oil to a temperature control pipe connected to the back surface of a mold to cool the mold.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a TPO powder slush molding method for an instrument panel skin will be described below with reference to the drawings.

As shown in FIG. 1, a molding die 1 used in the present molding method is made of a nickel alloy having concave corners 3 at several places on a deep concave molding surface 2 and a flange 4 on the periphery. It is a shell. This molding die 1 is manufactured by the method shown in (c) of paragraph 0016, and has a small straight hole 8 whose inner diameter is substantially constant in the hole length direction and an inner diameter that is continuous from the minute straight hole 8 and has a back surface. A large number of ventilation holes 7 are formed, each having a diameter-enlarging hole 9 that becomes larger toward the side.

The area S shown in FIG. 1A is a portion having a grain pattern, and as shown in FIG. 1B, a vent hole 7 (a minute straight hole 8) opened in the molding surface 2 as shown in FIG. Has a small inner diameter of about 100 μm. Further, a range K is a portion for forming an opening in the instrument panel skin, and as shown in FIG.
The inner diameter of the (small straight hole 8) is as large as about 150 to 200 μm. The range N is a neck portion to be cut off after molding,
In this portion, the inside diameter of the ventilation hole 7 (the minute straight hole 8) opened in the molding surface 2 is as large as about 150 to 200 μm.

As shown in FIGS. 2 (a), 3 (b) and 3 (c), a temperature control tube 10 is connected to the back surface of the molding die 1. The temperature control tube 10 is the same as that described in Japanese Patent Application Laid-Open No. 7-227851.
Reference numeral 11 denotes a wire net as a thin body, and 12 denotes an electroformed coating portion. As shown in FIG. 3A and the like, an airtight box 14 is placed on the back side of the mold 1, and the flange portion 4 is fixed to the airtight box 14 by welding or the like. T performed using this mold 1
The PO powder slush molding method will be described below in the order of steps.

As shown in FIG. 2A, the temperature control tube 10
Is supplied with oil heated to about 300 ° C. to heat the mold 1. As described above, the heating method is not limited to this method. For example, as shown in FIG. 2B, the molding die 1 can be heated by a burner flame 6 from a remote place outside.

Next, as shown in FIG. 3 (a), the molding die 1 is placed on the powder box 13 containing the TPO powder 20 with the molding surface 2 facing downward, and the flange 4 is attached to the powder box 1.
3 is fastened and fixed by a clamp 15. In addition, a vacuum pump (not shown) connected to the plug 16 of the airtight box 14 is operated to reduce the pressure on the back side of the mold 1, and the mold 1, the powder box 13 and the airtight box 14
Rotate several times in about 0 seconds.

As shown in FIG. 3 (b), when the TPO powder 20 is placed on the molding surface 2 which faces upward during rotation, the molten portion 21 which is brought into direct contact with the molten portion 21 and the molten portion 21
The heat is transmitted from and a semi-molten portion 22 that is semi-molten occurs,
On top of that is the unmelted TPO powder 20. As shown in FIG. 3C, when the molding surface 2 faces downward, the TPO powder 20 that has not melted falls and returns to the powder box 13. The initial adhesion thickness of the fused portion 21 and the semi-molten portion 22 is, for example, about 2 mm,
As the melting of the semi-molten portion 22 progresses and integrates with the molten portion 21, this thickness decreases.

After the rotation is completed, the powder box is removed from the mold 1 as shown in FIG. FIGS. 4 (b) and (c) correspond to FIG.
(C) shows a state in which the melting of the semi-molten portion 22 is further advanced to be integrated with the molten portion 21 to form an integrated TPO molten film 23 (however, some semi-molten portion 22 remains). , When the semi-molten portion 22 is completely melted
The thickness of the PO molten film 23 is, for example, 1.0 to 1.3 mm. As shown in FIG. 4 (b), the air 24 generated and contained by the mechanism (FIG. 8) in the flat portion of the TPO molten film 23 is released from the ventilation hole 7 by the above-mentioned pressure reduction.
It is sucked and removed on the back side of the. As shown in FIG. 4C, the gap 25 generated by the mechanism (FIG. 9) at the convex corner of the TPO molten film 23 is formed by the pressure reduction so that the TPO molten film 23 It is lost by being sucked. Therefore, a pinhole unlike the related art does not occur.

Subsequently, cooled oil is supplied to the temperature control pipe 10 to cool the mold 1 and the TPO molten film 23 is cured to form a TPO skin molded article 26. As described above, the cooling method is not limited to this method. For example, FIG.
In the case of the molding die 1 shown in FIG. 5, as shown in FIG. 5, the hermetic box 14 is removed from the molding die 1 (a structure capable of being removed in advance), and cooling is performed by applying water 27 to the back surface of the molding die 1. it can.

Next, the operation proceeds to the releasing operation. That is, FIG.
As shown in (a), the molding die 1 is placed on a receiving jig 18 having a receiving surface 17 one size smaller than the molding surface 2 with the molding surface 2 facing downward. The receiving surface 17 is provided close to the molding surface 2 so as to allow a clearance (interval) of, for example, about 10 mm. A sealing portion 19 conforming to the shape of the neck portion N is projected from the periphery of the upper surface of the receiving jig 18, and the neck portion of the TPO skin molded product 26 is pressed against the flange portion 4 of the molding die 1 to seal. It has become. By operating a compressed air pump (not shown) connected to the plug 16 of the airtight box 14 to pressurize the back side of the mold 1, the TPO skin molded article 2 strongly adhered to the molding surface 2 is formed.
6 is evacuated from the air holes 7 and peeled off from the molding surface 2.

FIGS. 6 (b) to 6 (d) show the states of the range S and the range K sandwiched by S during the compressed air.
As shown in (b), in the range K, since the inner diameter of the ventilation hole 7 opened to the molding surface 2 is large, about 150 to 200 μm, and the ventilation resistance is small, the TPO skin molded article 26 is particularly strongly pneumatically compressed. From the molding surface 2. Subsequently, as shown in (c) and (d), the TPO skin molded product 26
Is gradually peeled off and falls, but immediately below the receiving jig 18
Supported by the receiving surface 17.

As described above, the main part (most of the TPO skin molded product 26 except the neck portion N) is peeled off from the molding surface 2 by the compressed air, so that the adhesion of the TPO skin molded product 26 to the molding surface 2 is strong. Nevertheless, TPO skin molded product 2
6 can be easily peeled off, so that the TPO skin molded article 26 does not undergo elongation deformation or whitening. Also, TP
Since the main portion of the O-skin molded product 26 can be continuously peeled off without stopping, the unevenness does not occur and a single worker can sufficiently perform the release operation. Further, since the falling TPO skin molded product 26 is supported by the receiving surface 17 of the receiving jig 18 immediately below, the elongation deformation and the shape change are prevented.

Subsequently, from the mold 1 to the TPO skin molded article 2
Release 6 completely. That is, the receiving jig 18 is removed from the molding die 1, and the neck portion of the TPO skin molded product 26 that is in close contact with the flange portion 4 of the molding die 1 for the sealing is peeled off from the molding surface 2 by, for example, a manual operation.

Note that, as described above, the TP
It is preferable that a part of the O-skin molded product 26 be peeled off from the molding surface 2 by an ejector.

Further, as shown in FIG. 7A, the back side of the molding die 1 can be pressed without using a receiving jig. In this case, as shown in FIGS. 7B to 7C, there is no support when the TPO skin molded product 26 is peeled off and dropped, so that elongation deformation or shape change may occur, Will be cheaper.

It should be noted that the present invention is not limited to the above-described embodiment, and can be embodied by appropriately changing it without departing from the spirit of the invention.

[0044]

As described above, the TP according to the present invention is used.
According to the O powder slush molding method, the TPO molded product can be powder slush molded without generating pinholes, and the molded TPO molded product can be easily and quickly produced without any trouble from the molding die. It has an excellent effect that it can be released from the mold, thereby preventing elongation and whitening.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold used in an embodiment of the present invention.

FIG. 2 is a sectional view showing a step of heating the mold.

FIG. 3 is a cross-sectional view showing a step of attaching a TPO powder to the mold.

FIG. 4 is a cross-sectional view showing a step of removing air from a TPO molten film adhered to the mold and melted.

FIG. 5 is a sectional view showing another example of a method of cooling the mold.

FIG. 6 is a sectional view showing a step of releasing a TPO skin molded product from the molding die.

FIG. 7 is a cross-sectional view showing another example of the step of releasing the TPO skin molded product from the molding die.

FIG. 8 is a cross-sectional view illustrating a mechanism in which a pinhole is formed in a flat portion of a conventional TPO molded product.

FIG. 9 is a cross-sectional view showing a mechanism in which a pinhole is formed at a convex corner of a conventional TPO molded product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Molding surface 3 Concave corner part 4 Flange part 7 Vent hole 8 Micro straight hole 9 Enlarged diameter hole 10 Temperature control tube 13 Powder box 14 Airtight box 17 Receiving surface 18 Receiving jig 19 Seal part 20 TPO powder 21 Melted part 22 Semi-molten portion 23 TPO molten film 24 Air 25 Gap 26 TPO skin molded product

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F205 AA03 AA45 AC04 AH25 AH26 AM01 AM28 AM32 GA13 GB01 GC04 GE02 GE07 GF30 GN01 GN04 GN13 GN18 GN28 GN29

Claims (3)

[Claims] 1. A step of heating a mold having air permeability, and rotating the mold to form a T on a molding surface of the mold.
The TPO molten film is formed by contacting the PO powder, and the pressure on the back side of the mold is reduced to suck the TPO molten film to the molding surface to eliminate the gap and to remove the air contained in the TPO molten film by suction. A step of cooling the mold and curing the TPO molten film to form a TPO molded article; and a step of pressing the back side of the mold to evacuate the TPO molded article and peeling the TPO molded article from the molding surface. TPO powder slush molding method. 2. In the step of peeling off the TPO molded product from the molding surface, the TPO molded product peeled off from the molding surface is supported by a receiving surface which is one size smaller than the molding surface provided close to the molding surface. The method for forming a TPO powder slush according to claim 1. 3. The TPO powder slush molding method according to claim 1, wherein in the step of peeling the TPO molded product from the molding surface, a part of the TPO molded product is peeled from the molding surface by an ejector before the compressed air.