JP3611058B2 - Method for producing resin molded product having thick part and mold used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a molded article having a thick portion made of a thermoplastic resin and a mold using the same, and can be used when producing automobile interior / exterior products, furniture, chairs, building materials, and the like. is there.
[0002]
[Prior art]
In a molded product having a thick portion made of a thermoplastic resin, particularly an interior product such as an automotive instrument panel, the appearance such as the absence of sink marks on the surface of the molded product is regarded as important. On the other hand, in order to reduce costs, the number of parts has been actively reduced, and various bosses, ribs, clips, and the like are installed in the molded product, and appearance defects such as sink marks are likely to occur.
[0003]
Therefore, in order to suppress the appearance defect such as sink marks of molded products having partial thick parts such as bosses, ribs or clips, a method of preventing sink marks with a pressurized fluid or making the partial thick wall parts hollow, A method of delaying the cooling of the peripheral portion is disclosed.
In Japanese Patent Application Laid-Open No. 50-75247 or Japanese Patent Application Laid-Open No. 59-220337, a part having a thick portion such as a boss and a rib of a molded product is prone to sink on the outer surface. Is pressed against the mold surface with pressurized air to suppress the occurrence of sink marks, but in the case of molded products with long rib length, etc. There are problems such as inefficiency.
[0004]
In JP-A-7-148766, in molding in which a partial thick part is hollow, by using a part of a mold corresponding to the vicinity of the thick part as a heat insulating material, cooling near the thick part is delayed, Although a method of eliminating the difference in gloss between the product surface corresponding to the thick part and the vicinity thereof is disclosed, it is premised on that the thick part such as a rib that requires strength is made hollow, and is made hollow. In some cases, permeation easily occurs and the strength is insufficient.
[0005]
[Problems to be solved by the invention]
The present invention has a thick part such as a boss, a rib or a clip, and in a molded product in which sink marks are likely to occur on the outer surface, a heat insulating material is provided at a location corresponding to the vicinity of the base of the thick part. By using a mold, the cooling near the base of the thick part is delayed, and by adopting a molding method that presses the base of the thick part and the vicinity of the base against the mold with pressurized fluid, the occurrence of sink marks is prevented. For the purpose.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, among the present invention, the first invention is a molding of a molded product having a partial thick portion, and a partial thick portion protruding to the back side of the molded product; And a pressurized fluid inlet that opens on the back side of the molded product away from the base of the thick part, and a portion corresponding to the back side of the base of the thick part is formed of a heat insulating material, and Using a mold in which a part of the material is extended to the injection port along the back surface of the molded article, the cooling of the resin near the base of the thick wall portion is delayed by the heat insulating material from the cooling of the surrounding resin, and The base of the thick part and the vicinity of the base are pressed against the mold on the front side of the molded product from the back side of the molded product by the pressurized fluid injected between the back surface of the molded product and the heat insulating material from the inlet , A method of manufacturing a resin molded product characterized by preventing sink marks on the surface of the molded product It is intended to provide.
[0007]
2nd invention is a metal mold | die for manufacturing the resin molded product which has the partial thick part protruded on the back surface side. Pressurized fluid opened to the back surface side of the molded product away from the base part of the thick wall portion. as well as have the inlet, mold portion corresponding to the back surface side of the thick base portions is formed with a heat insulating material, and a portion of the heat insulating material is extended to the inlet along a back surface of the molded product And the pressurized fluid which is delayed between the cooling of the resin in the vicinity of the base of the thick wall portion by the heat insulating material from the cooling of the surrounding resin and injected between the back surface of the molded product and the heat insulating material from the injection port. Thus, a mold for a resin molded product is provided which is configured to be able to press the base of the thick portion and the vicinity of the base from the back side of the molded product to the mold on the front side of the molded product. .
[0008]
The thick part in the present invention is a thick part in which a boss, rib, clip, or the like protrudes from the surface of the main part of the molded product, and if it is integrally formed with the molded product, its shape, function, etc. It is not limited to. This clip is, for example, a clip that is formed integrally with a resin wheel cap of an automobile and used for mounting on a wheel.
[0009]
The base portion of the thick portion in the present invention means the rib base 102 shown in FIG. 1 or the base of a boss or clip corresponding thereto. The vicinity of the base means the vicinity 103 of the rib base corresponding to the location where the heat insulating material is provided. Also, it means the vicinity of the base of the corresponding boss or clip. The area around it is more distant from the base than near the base.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a molded article having a partial thick portion in which bosses, ribs, clips, or the like formed by injection molding, injection compression molding, or gas injection injection molding are variously installed. For example, interior parts such as an instrument panel of an automobile provided with a large number of ribs by gas injection injection molding as shown in FIG.
[0011]
In the present invention, the following resin, mold, molding machine and molding method can be employed.
The target resins include thermoplastic resins such as polyethylene, polypropylene, ABS, polycarbonate, and polyamide, or elastomers such as ethylene / α-olefin copolymer elastomers, talc, mica, calcium carbonate, and glass fibers. In addition, a material added with an inorganic filler such as carbon fiber can be employed, and a polypropylene resin is mainly employed in many cases.
[0012]
A mold for a resin molded product having means for feeding a pressurized fluid around the back side of the thick part base of the present invention, wherein a part of the mold corresponding to the back side of the thick part base is provided with a heat insulating material As shown in FIGS. 1, 2 and 5, the mold for the resin molded product in which a part of the heat insulating material reaches the vicinity of the pressurized fluid injection portion into the cavity can be considered, and will be described in detail below. To do.
[0013]
The material of the mold body may be a carbon steel material or the like used in a normal injection mold.
The heat insulating material provided in the mold makes it difficult for the heat of the resin injected into the cavity to be transmitted to the mold, and has a lower thermal conductivity than the mold material, and the temperature of the molten resin and sliding for taking out the molded product Adopt one that can withstand. For example, polyimide resin, epoxy resin, silicon resin, tetrafluoroethylene resin, ceramics, etc. can be employed.
[0014]
In addition, this heat insulating material may be a porous material having air permeability, but it is a hole that does not allow the molten resin to enter, and does not cause a problem in taking out the molded product. It is necessary to have a structure that does not leak.
The size of the heat insulating material cannot be generally defined by the thickness of the thick part such as the boss, rib or clip, or the thickness of the molded product, but the thickness of the thick part is 0.5 to 3 times the thickness of the thick part. A height of 0.1 to 2 times the height is preferable.
[0015]
As shown in FIG. 1, the mounting position is set in the vicinity of the base corresponding to the boss, the rib, the clip, or the like on the side where the boss, rib, or clip is installed. Depending on the shape of the molded product and the required thickness of the heat insulating material, it may be embedded in the mold as shown in FIGS. 1 and 5 (a) to (c), When the thickness may be small, it may be attached to the mold surface as shown in FIG.
Further, when the height of the boss, rib or clip is low, it may be provided so as to surround the boss, rib or clip as shown in FIG.
[0016]
A mold having a means for sending pressurized fluid around the back side of the thick wall base is a pin-like inlet or porous member having a gap that does not allow molten resin to flow in and allows the pressurized fluid to sufficiently flow Is provided in the vicinity of the boss, rib, clip, or the like of the molded product. The gaps and holes that do not allow the molten resin to flow in have a size of 5 to 80 μm. Depending on the shape required for the molded product, these inlets may be the same height as the surface around the inlet, or the groove may be formed to the position of the boss, rib or clip where the pressurized fluid is to be sent. It may be provided and may have a height that matches the surface. The shorter the distance from the inlet to the boss, rib, or clip, the more effective, but it is set as appropriate depending on the shape of the molded product and the position of the boss, rib, or clip. Moreover, it is preferable to provide the above-described heat insulating material in a mold from the inlet to the boss, rib, clip, or the like.
[0017]
The above-described mold is supplied with pressurized fluid from a separately provided pressurized fluid supply device. The pressure, supply speed, supply timing, pressure holding time, and the like are controlled by a control system of the supply device. The conditions need to be adjusted as appropriate depending on the size, shape, etc. of the molded product, but the pressure of the pressurized fluid, the timing of applying pressure, so that the strength near the base of the rib portion is not impaired, It is better to set the holding time. The pressure of the pressurized fluid is low in the initial stage of cooling and solidification immediately after the molten resin is injected and filled, so that the pressurized fluid does not break through the thin solidified layer and enter the resin, and solidify to some extent. In this state, it is preferable to increase the pressure of the pressurized fluid and sufficiently press the base of the thick part and the molten resin in the vicinity thereof from the back side of the molded product to the mold forming surface on the front side of the molded product.
Further, in anticipation of the above-described thinning, it is preferable to widen the base portion of the rib portion in a tapered shape to ensure the thickness of the rib portion and reinforce it.
[0018]
As the pressurized fluid, pressurized nitrogen gas, dry air, or the like can be used. Nitrogen gas that is safe against compression and heating is preferred.
The molding machine may be a normal injection molding machine, injection compression molding machine or gas injection injection molding machine suitable for each molding.
[0019]
Using the above-described mold, a molded product having a partially thick part can be molded as follows.
(1) Corresponding to the shape of the molded product, using a mold provided with the above-mentioned heat insulating material and injection port, the molten resin is injected into a mold that is clamped by a normal injection molding method. Fill.
(2) When the filling is completed or a delay time is provided by a delay timer, a pressurized fluid is supplied from the injection port of the mold, and a molten resin corresponding to the mold molding surface provided with a heat insulating material and the back surface of the molded product Press fit between. Depending on the shape of the molded product, the pressurized fluid may be supplied before injection filling.
(3) The pressurized fluid is selectively guided to a place where the cooling of the resin is delayed by the material having low thermal conductivity provided in the mold, and efficiently near the base of the thick part (boss, To reach the base of the rib or clip). The pressurized fluid presses the molten resin in the vicinity of the base portion of the thick wall portion where the cooling is delayed from the back surface side of the molded product to the mold forming surface on the front surface side of the molded product. Thereby, the base part of a thick part is also pressed from the back surface side of a molded product to the metal mold forming surface of the surface side of a molded product.
(4) Holding the pressure fluid for a predetermined time while holding it with pressure, the molten resin is cooled and solidified to prevent sink marks on the surface of the molded product corresponding to the base of the thick portion. Then, depressurize.
(5) When the mold is opened, the pressurized fluid is left pressurized to an extent that facilitates mold release, and the mold is opened to remove the molded product from the mold.
[0020]
As described above, in the present invention, the pressurized fluid is selectively guided to the location where the cooling of the resin is delayed by the low thermal conductivity material provided in the mold, and the thick-wall base is efficiently provided. The pressurized fluid presses the base portion of the thick wall portion where the cooling is delayed and the molten resin in the vicinity thereof from the back surface side of the molded product to the mold forming surface on the front surface side of the molded product. Holding the pressure for a predetermined period of time, the molten resin is cooled and solidified to prevent sink marks on the surface of the molded product corresponding to the base of the thick portion.
[0021]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In order to increase the strength of the panel structure in addition to the gas channel 118, a part of the rib 101 is provided in the instrument panel of the automobile by gas injection injection molding as shown in FIG. Rib 101 as shown in FIG.
This instrument panel can be molded by a gas injection molding machine as shown in FIG. Nitrogen gas is used as the pressurized fluid, and it is connected so as to be supplied to the pressurized fluid supply port 114 from the branch passage 26A branched from the holding pressure gas passage 26 of FIG.
[0022]
As described above, the mold 2 for molding this is provided with the heat insulating material 110 and the pin-shaped inlet 112 near the base 103 of the rib.
The heat insulating material 110 uses Teflon having low thermal conductivity, and is embedded from the pin-shaped inlet 112 to the rib and on both sides 103 near the base of the rib as shown in FIGS.
[0023]
The pin-shaped inlet 112 is configured to coincide with the surface of the mold 103. A cylindrical pin 113 smaller than this hole is provided in a circular through hole on the surface of the mold 108, and the opposite side of the injection port is sealed with a seal member 115. Thereby, the injection port 112 forms a slit, and the slit is a gap having a size of about 50 μm. Further, a reservoir 116 of pressurized fluid is provided so that the pressurized fluid can be stably injected from the slit.
[0024]
In this molding, first, a mold 107, a part of which is shown in FIG. 1, is clamped, and a molten resin 117 is injected into the mold from a gas injection injection molding machine (not shown) to perform gas injection.
After the injection filling is completed, a pressurized fluid made of nitrogen gas is supplied from the pin-shaped inlet 112. The portion in contact with the heat insulating material 110 is where the cooling is delayed more than the heat insulating material and the formation of the solidified layer is not so advanced, so that a slight deformation occurs due to the pressure of the pressurized fluid, and the injection filled molten resin 117 and the mold 108. A gap is generated between and the pressurized fluid reaches the vicinity 103 of the rib base. As a result, the pressurized fluid presses the rib base 102 and the vicinity 103 of the rib delayed in cooling from the back surface side of the molded product against the surface of the mold 109 in contact with the surface of the molded product.
[0025]
The process of holding the pressure while continuing to pressurize the pressurized fluid, and the process of holding the pressure while maintaining the pressure of the pressurized fluid after stopping the pressurization of the pressurized fluid, And release the pressure inside the mold. As a result, sink marks on the surface of the molded product can be prevented.
The pressurization of the pressurized fluid is left to an extent that facilitates mold release, the mold is opened, and the molded product is removed from the mold.
[0026]
【Example】
Hereinafter, the present invention will be described with reference to specific examples.
[Embodiment 1] In Embodiment 1, a large molded product having ribs as thick portions is molded as follows based on the present invention.
(1) Molded product The automobile instrument panel of FIG. 3 has ribs in part.
(2) Used resin Idemitsu polypropylene (J-762HP, MI = 10 g / 10 min; 230 ° C., 2.16 kgf) was used.
(3) Mold used A mold corresponding to the instrument panel of the automobile shown in FIG. 3, and a heat insulating material made of Teflon and an inlet for pressurized fluid are provided at locations corresponding to the ribs as shown in FIG. . The slit has a size of 50 μm.
(4) Molding machine used An injection molding machine (IS2200DF, mold clamping force 2200ton) manufactured by Toshiba Machine is used to supply pressurized fluid from a gas supply device as shown in FIG.
[0027]
(5) Molding conditions The molding conditions were as follows.
a) Resin temperature: 220 ° C
b) Mold temperature: 40 ° C
c) Injection time: 5 seconds d) Cooling time: 40 seconds e) Gas injection conditions (injected into gas channel 118, using gas for forming hollow, nitrogen gas)
・ Gas injection pressure: 10 MPa
-Gas injection timing: 4 seconds after the start of resin injection-Gas injection time: 2 seconds-Gas retention time: 20 seconds-Gas depressurization time: 10 seconds f) Pressurized fluid injection conditions (for the prevention of sink marks of the present invention) (Uses pressurized fluid and nitrogen gas)
・ Gas injection pressure: 4MPa
Gas injection timing: 0.5 seconds after completion of injection filling Gas injection time: 25 seconds Gas holding time: 10 seconds Gas decompression time: 5 seconds (6) Evaluation results Molding by sink as shown in FIG. A molded product having no appearance of a concave portion on the surface of the product and having a good appearance was obtained. (The solid line in FIG. 6 shows the cross section of the molded product, and the broken line shows the mold shape.)
[0028]
[Comparative Example 1] For comparison with Example 1, a conventional mold (the material of the mold is carbon steel) in which no heat insulating material is provided between the position corresponding to the rib portion and the position to the injection port is used. Except that, molding was performed in the same manner as in Example 1.
The nitrogen gas injected from the inlet spread concentrically around the inlet, and the nitrogen gas holding pressure at the base of the rib corresponding to the base of the thick wall portion was significantly reduced. As a result, cooling of the thick portion of the base portion progressed, and sink marks were generated on the surface of the molded product corresponding to the rib portion as shown in FIG. (The solid line in FIG. 7 shows the cross section of the molded product, and the broken line shows the mold shape.)
[0029]
【The invention's effect】
According to the present invention, a mold provided with a heat insulating material is provided at a location corresponding to the vicinity of the base portion of the thick wall portion, the cooling of the base portion of the thick wall portion is delayed, and the base portion of the thick wall portion and the vicinity of the base portion are molded. Adopting a molding method that presses against the surface with a pressurized fluid, even in molded products that have partial thick parts such as bosses, ribs or clips, and where the outer surface is prone to sink, Good molded products can be molded.
[Brief description of the drawings]
FIG. 1 is a schematic view around a rib portion in the present invention.
FIG. 2 is a cross-sectional view (AA ′ cross section in FIG. 1) of the rib portion and the injection port in the present invention.
FIG. 3 shows a schematic view of an instrument panel of an automobile.
FIG. 4 is a schematic view of a gas injection injection molding machine and a gas supply device.
FIG. 5 shows a conceptual diagram of arrangement of heat insulating materials in the present invention.
FIG. 6 is a cross-sectional view of a rib portion in an embodiment of the present invention.
FIG. 7 is a cross-sectional view of a rib portion in a comparative example.
[Explanation of symbols]
101 ... Rib 102 ... Rive root 103 ... Rib base vicinity (Back side of molded product)
104... Lack of gas due to gas holding pressure 105... Rib thickness 106... Rib height 107... Mold 108. Surface side mold 110 ... heat insulating material 111 ... pressurized fluid supply mechanism 112 ... pin-shaped inlet 113 ... pin 114 ... pressurized fluid supply port 115 ... seal member 116: Accumulated fluid reservoir 117: Filled resin 118 ... Gas channel

Claims (2)

In molding a molded product having a partial thick part,
The thick part has a partial thick part protruding to the back side of the molded product and a pressurized fluid inlet opening on the back side of the molded part away from the base of the thick part, and the base part of the thick part Using a mold in which a part corresponding to the back surface side is formed of a heat insulating material, and a part of the heat insulating material is extended to the inlet along the back surface of the molded product,
The cooling of the resin near the base of the thick wall portion is delayed by the heat insulating material from the cooling of the surrounding resin, and the thickness is increased by the pressurized fluid injected between the back surface of the molded product and the heat insulating material from the inlet. A method for producing a resin molded product, characterized in that a base portion of the meat portion and the vicinity of the base portion are pressed from a back surface side of the molded product to a mold on a front surface side of the molded product so as not to cause sink marks on the surface of the molded product. In a mold for producing a resin molded product having a partial thick portion protruding on the back side,
As well as have the inlet opening and the pressurized fluid to the rear surface side of the molded product away from the base of the thick portion, the portion of the mold corresponding to the rear surface side of the thick base portions is formed with a heat insulating material, and heat insulation A part of the material is extended to the injection port along the back surface of the molded product,
The cooling of the resin near the base of the thick wall portion is delayed by the heat insulating material from the cooling of the surrounding resin, and the thickness is increased by the pressurized fluid injected between the back surface of the molded product and the heat insulating material from the inlet. A mold for a resin molded product, characterized in that the base portion of the meat portion and the vicinity of the base portion can be pressed from the back surface side of the molded product to the mold on the front surface side of the molded product.

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