JPH0788878A - Injection foam molding method - Google Patents

Abstract

PURPOSE:To obtain a foam cell having a desired size in proper magnification by controlling the mold opening speed while the space between molds is expanded so as to change the same stepwise from a high speed after the start of mold opening to a low speed before the completion of mold opening. CONSTITUTION:Molds A, B are respectively fixed to a fixed plate 1 and a movable plate 2 to form a space D. When a resin containing a foaming agent is injected into the space D, the distance between the molds A, B is increased by a stroke l and the space D is expanded so as to permit foaming. The expanding speed of the space D is set by the control of a mold opening speed controller 13 to a hydraulic unit 11 with respect to a cylinder device 3. The expanding speed is controlled so as to be high at the time of mold opening and made low before the completion of mold opening. By this constitution, foaming magnification is increased at the time of the start of mold opening and the close contact degree of a skin layer to the surfaces of the molds due to foaming force is enhanced in such a state foaming force before the completion of molding opening is low to improve the surface state of a molded product. Therefore, the molded product having a soft surface feeling is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile interior panel (instrument panel, door panel, seat back panel, steering wheel, handle, etc.), furniture (chair seat, etc.), sundries (shoes, slippers, etc.). As described above, a foamed molded article in which a skin layer on the surface and a foamed layer on the inside are formed, and a foamed layer and a skin layer are formed on one surface of a hard resin core material, if necessary, by an injection molding machine. More particularly, it relates to a method capable of controlling a foaming state of a foamable resin to obtain a molded product having a desired feel and a good surface.

[0002]

2. Description of the Related Art Conventionally, as the foam injection molding method,
The one disclosed in Japanese Patent Publication No. 51-8424 is known. After injecting a resin containing a foaming agent into the space of the mold held so that the mold can be opened, the space is expanded by opening the mold to foam the resin, and the cooled and solidified skin on the mold surface side A method for obtaining a foam-molded article having a layer and a foam layer on the inner side of the mold. This foam injection molding method discloses a circuit configuration in which the mold opening speed can be changed for each injection by providing a flow rate control valve in the mold opening hydraulic circuit. It is not intended to change.

In recent years, attempts have been made to apply this foam injection molding method to the molding of the above-mentioned automobile interior panel. This is because the yield of the resin is higher than in the case where the skin layer is separately formed by a vacuum forming method or the like, and it is possible to form the skin layer in a continuous process.

In particular, panels for automobile interiors are required to have a soft surface and a soft feel. In order to obtain this feel, the selection of materials is also important, and a thermoplastic elastomer that has rubber-like elasticity at room temperature and can be injection-molded at high temperature is used as a material for forming the skin layer and the foam layer. Tried to use (unpublished).

[0005]

However, when the conventional foaming injection molding method is applied to molding of a thermoplastic elastomer, the foaming ratio or the size of the foaming cell is not appropriate, and the desired feeling is obtained. In addition, there is a problem that a good surface condition cannot be obtained. In JP-A-48-22164 and JP-A-49-10967, it is conceptually known that the foaming ratio is controlled by controlling the time from the completion of injection to the start of mold opening. Is not enough.

Therefore, the present invention is based on the findings obtained through many experiments. The purpose of the present invention is to ensure an appropriate expansion ratio and foam cell state, and An object of the present invention is to provide a foam injection molding method capable of obtaining a foam molded article having a feeling.

[0007]

A foam injection molding method for solving the above-mentioned problems is achieved by injecting a resin containing a foaming agent into a space in a mold held so that the mold can be opened, and then opening the mold. In a foam injection molding method for expanding a space to foam a resin to obtain a foam-molded article having a cooled and solidified skin layer on the mold surface side and a foam layer on the mold inner side, while expanding the space. It is a method of controlling foaming by changing the mold opening speed, and the change of the mold opening speed is in multiple stages including a high speed after starting the mold opening and a low speed before completing the mold opening, or during the mold opening. The pressure in the space is measured, and the pressure in the space is compared with a predetermined pressure pattern. When the pressure is high, the mold opening speed is increased, and when it is low, the mold opening speed is decreased. In addition, the resin containing the foaming agent is an elastomer, and after the core material of the hard resin is completely filled and injected into the mold including at least one of the molds, the mold is formed between the mold and the other mold. A space is formed, or a preformed core material is attached to a mold having a larger void than the core material to form the space inside the mold.

This method is suitable for molding thermoplastic elastomers containing a blowing agent. In addition, a mold inner space is formed between a mold including at least one of the molds and a hard resin core material after the core material is completely filled and injected (two-layer molding / mold space expansion). Method) or a preformed core material is attached to a mold having a larger void than this core material to form the mold internal space (insert / mold space expansion method). .

Particularly, as the expandable thermoplastic elastomer, a melt tension at 190 ° C. of 1.5 based on a hydrogenated product of a styrene / conjugated diene block copolymer is used.
kg or more, melt spreadability of 100 m / min or more, and JI
It is preferable to use 100 parts by weight of a styrene-based thermoplastic elastomer component having a JIS-A hardness of 30 to 95 according to S.K6301 and 0.5 to 10 parts by weight of a foaming agent component.

[0010]

When the mold is opened at high speed, the foam cells become large, and when the mold is opened at low speed, the foam cells become small. That is, the size of the foam cells and the foaming ratio are adjusted by changing the speed at which the space filled with the foamable resin is expanded. However, if the mold opening speed is determined only by the state of foaming, the foaming force is low before the completion of mold opening, and if the mold opening speed remains after the start of mold opening, the surface of the skin layer will open the mold. It was found that the mold and the skin layer did not follow the speed and the surface condition such as the texture transfer property deteriorates. Therefore, when the foaming force at the beginning of mold opening is strong, the mold opening speed is set to a predetermined mold opening speed so that a desired expansion ratio and a desired size of foam cells can be obtained, and the foaming force before completion of mold opening is low. Then, when the mold opening speed is lowered, the adhesion of the skin layer to the surface of the mold due to the foaming force is improved, the surface condition is improved, and a foaming cell having a desired expansion ratio and a desired size can be obtained. Therefore, it is most preferable to perform feedback control of the mold opening speed so that a desired predetermined pressure pattern in the mold is maintained.

When the foaming is controlled by changing the mold opening speed within one shot using the above-mentioned specific thermoplastic elastomer, the desired foaming ratio and good surface condition give the appearance and feel similar to natural leather. It becomes a foam molded product.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, a molding machine to which the foam injection molding method of the present invention is applied will be described with reference to FIG. 4, and then the foam injection molding method will be described with reference to FIGS. 1 to 3.

In FIG. 4, molds A and B which are openably and closably fitted to each other are fixed to a pair of a fixed platen 1 and a movable platen 2 facing each other, and a space containing a resin containing a foaming agent is injected. D is formed. Further, after the resin containing the foaming agent is injected from the known injection device C, the distance D between the molds A and B is opened by the stroke l so that the space D can be expanded to allow foaming inside. There is. Therefore, the fixed plate 1 is provided with the cylinder device 3, the extension rod 5 is connected to the thrust rod 6 via the micrometer head 7, and the rod 6 is fixed to the movable plate 2 by the nut 9a. Further, in order to withstand the injection pressure of the injection device C, the pressurizing cylinder 8 presses the movable platen 2 against the fixed platen 1 via the tie rod 4.
However, the pressing force of the pressurizing cylinder 8 after the completion of injection decreases,
The pressing force of the cylinder device 3 is lowered, and the dies A and B are opened by the cylinder device 3 to expand the space D described above.

In order to control the mold opening speed of the molds A and B (corresponding to the expansion speed of the space), the hydraulic unit 11 for the cylinder device 3 is provided with a flow rate control valve 12, and this flow rate control valve 12 is provided. It is controlled by the mold opening speed controller 13. The mold opening speed of the molds A and B can be controlled by time or stroke. When controlling by stroke, an encoder 9 is provided and the output thereof is input to the mold opening speed controller 13. In addition, the time from the completion of injection to the start of mold opening is timer 14
Is set by.

Next, a foam injection molding method based on a concrete experiment will be described below. 27% by weight of a hydrogenated product of a styrene / butadiene block copolymer [styrene / ethylene / butylene / styrene copolymer “SEBS” (average molecular weight 85,700, styrene content 29%)] as a styrene-based thermoplastic elastomer component. Paraffin oil (average molecular weight 746, ring analysis 0
%) Is 33% by weight. Flexural modulus according to JIS-K7203 is 10,100.
kg / cm ² and MFR (230 ° C, 2.16k
g) is 20% by weight of ethylene / propylene block copolymer having a content of 1.5 g / 10 min, density 0.919 g / cm ³ , and MFR (190 °
C, 2.16 kg) having a composition of 20% by weight of low-density polyethylene of 4 g / 10 min and having a JIS-A hardness of 80 was used. A blowing agent masterbatch containing 20% by weight of a mixture of an inorganic salt and an organic acid (“FineBlow S20N” manufactured by Mitsubishi Petrochemical Co., Ltd.) was added to the styrene thermoplastic elastomer component in an amount of 4 parts by weight. A blowing agent masterbatch containing 20% by weight of acid amide (“FineBlow MX87” manufactured by Mitsubishi Yuka Co., Ltd.) was included in an amount of 1 part by weight with respect to the styrene-based thermoplastic elastomer component, and the gold surface temperature was 40 °. It was set to C and the mold opening speed during one shot was changed to obtain a foam-molded article.

As shown in FIG. 1 (a), the mold opening speed v1 is fast until time t1 and the mold opening speed v is slow at times t1 to t2.
In the case of the two-step control of 2 (solid line), a foaming ratio or a skin layer having an arbitrary surface condition was obtained. The result of measuring the pressure in the mold in this case with the pressure sensor is shown by the solid line in FIG. A substantially uniform pressure is maintained during foaming, the in-mold pressure is maintained until the time t2 when foaming is completed, and the skin layer follows the opening of the mold.

As shown in FIG. 1 (a), in the case of the one-step control (dashed line) in which the mold opening speed v2 is slow until the time t2,
As shown by the alternate long and short dash line in FIG. 1 (b), the pressure inside the mold rapidly increases and a thick skin layer is formed. In the case of the one-step control (dotted line) in which the mold opening speed v1 is fast until the time t2 as shown in FIG. 1 (a), the in-mold pressure during foaming becomes substantially uniform as shown by the dotted line in FIG. 1 (b). However, it can be seen that the pressure inside the mold becomes zero before the completion of foaming, and the skin layer does not follow the opening of the mold.

That is, in order to obtain a foamed molded article having a good feel due to proper foaming and an appearance due to good transfer, there is a proper pressure pattern in the mold. Therefore, in FIG.
In order to obtain the pressure pattern as shown by the solid line in FIG.
A pressure sensor (not shown) is provided on each of the molds A and B, and the mold speed controller 13 compares the pressure pattern with the pressure pattern. The mold opening speed is increased when the mold pressure is high, and the mold speed is decreased when the mold pressure is low. By performing feedback control that the opening speed is slowed, a desired favorable foam-molded article can be obtained.

Next, the relationship between the mold opening speed after the start of mold opening and the expansion ratio will be described with reference to FIGS. 2 and 3. In FIG. 2, when the mold opening speed after starting the mold opening is slow, the foaming ratio is low,
The higher the mold opening speed, the higher the expansion ratio. Figure 3
As shown in (a), when the mold opening speed is less than 0.5 mm / sec, the mold opening speed is too slow as compared with the cooling rate of the resin, so that the skin layer a becomes thick and the foam layer b becomes extremely thick. Thins. Further, as shown in FIG. 3C, the mold opening speed is 10
When it exceeds mm / sec, the skin layer a is extremely thin, the skin layer a cannot follow the opening speed of the mold, and wavy, and the foam cells c in the foam layer b are also uneven. However, as shown in FIG. 3B, the mold opening speed is 0.5 to 10 mm /
When it is sec, the skin layer a and the foam layer b are well balanced, the surface state of the skin layer a is good, and the foam cell c
Is also uniform.

In the above description of the embodiments, the foam injection molding method of the foam-molded article in which both sides of the foam layer are the skin layers is explained. However, the foam layer and the skin layer are formed on one side of the core material made of a hard resin. This foam injection molding method can be applied to a laminated body such as an instrument panel in which the above is formed.

A molding machine for obtaining such a laminated body in a series of steps will be described with reference to FIG. In FIG. 5, the molding machine has a skeleton composed of a bed 101, a crown 102, and a stand frame 103.
A bolster 10 on which two lower molds, a first lower mold 105 and a second lower mold 106 are mounted, is provided on the upper part of the unit 1.

The bolster 107 is movable in parallel by a driving device (not shown), and the first lower mold 105 is located at the center of the molding machine and the first position shown by the solid line and the second lower mold 106 are located at the center of the molding machine. And a second position indicated by a chain double-dashed line. An elevating cylinder 111 and an adjusting cylinder 112 are fixedly mounted on the crown 102, and the slide 1 is attached to the ends of the piston rods 111a and 112a of the elevating cylinder 111 and the adjusting cylinder 112.
14 is fixed. Then, the upper mold 115 is attached to the slide 114, and by operating the elevating cylinder 111, the upper mold 115 is moved to the lower mold 105,
It can be raised and lowered toward 106. Further, by operating the adjusting cylinder 112, the upper die 115
Can be slightly moved up and down toward the lower molds 105 and 106. Equilibrium support devices 118 are arranged at the four corners of the bed 101, and the slide 114 is supported by the equilibrium support devices 118 in equilibrium with respect to the bed 101. Further, on the side of the molding machine, the first lower mold 1
05, a first injection unit and a second injection unit (not shown) for supplying the molding material to the second lower mold 106 are installed.

Next, a method of manufacturing a laminated body using the molding machine having the above structure will be described with reference to FIG. Figure 6 (a)
, The bolster 107 is moved to the second position, the piston rod 111a of the lifting cylinder 111 is extended to lower the upper mold 115 toward the second lower mold 106, and The second cavity 125 is formed with the second lower mold 106. Then, as shown in FIG. 6B, a core material of a thermoplastic resin is supplied to the second cavity 125 from a second injection unit (not shown) to supply the core material 125.
To mold. When the molding is completed, as shown in FIG. 6C, the piston rod 111a of the elevating cylinder 111 is left with the molded core material 126 left in the upper mold 115.
To raise the upper mold 115, and the bolster 107
Move to the first position.

Then, as shown in FIG. 7 (a), the upper mold 115 with the piston rod 111a of the elevating cylinder 111 extended and the core material 126 attached is used as the first lower mold 1.
05 toward the core material 126 and the first lower mold 10
The first cavity 128 is formed with 5. And FIG.
As shown in (b), the foam material 1 such as the above-mentioned foaming agent-containing styrene elastomer is added to the first cavity 128.
29 is injected and filled at a predetermined injection pressure. And FIG.
As shown in (b), the adjustment cylinder 112 is moved from this state.
Of the first cavity 12 by shortening the piston rod 112a of the
When the space of 8 is increased, the pressure of the foam material 130 is reduced to the foaming critical pressure or less, and foaming occurs inside the foam material 130 to form the foam layer 132. Further, the foam material 130 in the portion in contact with the first lower mold 105 is cooled and solidified in an unfoamed state, and the hard skin layer 13 that is not foamed.
3 is formed. Then, in this way, the core material 126
When the foam layer 132 and the skin layer 133 are integrally laminated on the piston rod 11 of the lifting cylinder 111.
1a is shortened and the upper die 115 is raised, and the core material 126
One cycle of molding is completed by taking out the laminated body including the foam layer 132 and the skin layer 133.

In this way, the foam material 130 is filled between the core material 126 and the first lower mold 105 and foamed while leaving the core material 126 in the upper mold 115 in which the core material 126 is molded. The first cavity 128 is formed to expand the space for cooling and solidification, and the foam layer 132 and the skin layer 133 are integrally laminated and formed on the core material 126.
It is possible to continuously manufacture a laminated body composed of No. 6, the foam layer 132, and the skin layer 133 with one molding machine, and it is possible to significantly reduce the number of steps. Further, since the core material 126 is molded from the molding material, there is almost no material loss, and the yield is significantly improved. Therefore, it is most suitable as a method for manufacturing a laminated body having a large and complicated shape such as an automobile interior panel, particularly an automobile instrument panel. Furthermore, when similar materials are used for the core material and the foam material, the adhesion between the core material and the foam layer is improved, and recycling is possible.

The core 126 described above is injection-molded by using one of the molds in common (two-layer molding / mold space expansion method).
However, a space is formed after a pre-injection-molded core material is installed in a mold that can open the mold (insert,
Type space expansion method).

[0027]

EFFECT OF THE INVENTION The foam injection molding method of the present invention controls foaming by changing the mold opening speed (space expansion speed) during one shot, and foam cells are foamed in an appropriate size. When the expansion ratio is appropriate and the foaming force before the completion of mold opening is low, the mold opening speed is reduced to increase the adhesion of the skin layer to the mold surface due to the foaming force to improve the surface condition. Further, it is possible to obtain a foamed molded product having a soft feel and having a good surface condition such as a texture transfer property.

When an elastomer (preferably a styrene elastomer) is used as the resin containing the foaming agent, a foam molded article having a good appearance and feel similar to natural leather can be efficiently molded at low cost. In particular, it is suitable for a molding method for mass-produced products such as automobile interior panels.

[Brief description of drawings]

FIG. 1 is a graph showing a two-step control of high and low mold opening speed.

FIG. 2 is a graph showing a relationship between a mold opening speed and a foaming ratio.

FIG. 3 is a cross-sectional view showing a change of a foam-molded article depending on a mold opening speed.

FIG. 4 is a schematic view of a molding machine to which the foam injection molding method of the present invention is applied.

FIG. 5 is a schematic view of another molding machine to which the foam injection molding method of the present invention is applied.

FIG. 6 is a diagram showing a molding process by another molding machine.

FIG. 7 is a diagram showing a molding process by another molding machine.

[Explanation of symbols]

 12 Flow control valve A, B Mold C Space a Skin layer b Foam layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B29K 105: 20 B29L 9:00 31:44 31:50 31:58 (72) Inventor Masahiko Kashiwa Hyogo 2-3-1, Niihama, Arai-machi, Takasago-shi, Takasaki, Kobe Steel Works (72) Inventor Takeshi Nagaoka 2-3-3, Niihama, Arai-machi, Takasago-shi, Hyogo (72) Invention Person Masayoshi Ueda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Naoki Murase 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Keiichi Hasegawa Toyota City, Aichi Prefecture Toyota Town No. 1 Toyota Motor Corporation (72) Inventor Ryoichi Ito No. 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute (72) inventor Izumi Ishii Yokkaichi, Mie Prefecture Toho-cho, the first address by Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute in

Claims (4)

[Claims] 1. After injecting a resin containing a foaming agent into a space inside a mold held so that the mold can be opened, the space is expanded to expand the resin by opening the mold, and In a foam injection molding method for obtaining a foam molded article having a cooled and solidified skin layer and a foam layer on the inner side of the mold, a method of controlling foaming by changing a mold opening speed while expanding the space. Foam injection molding method. 2. The foam injection molding method according to claim 1, wherein the change of the mold opening speed is multistage including a high speed after starting the mold opening and a low speed before completing the mold opening. 3. The change of the mold opening speed is performed by measuring the pressure in the space during the mold opening and comparing the pressure in the space with a predetermined pressure pattern. The foam injection molding method according to claim 1, wherein the mold opening speed is lowered. 4. The resin containing a foaming agent is a thermoplastic elastomer, and a mold containing at least one of the molds is completely filled with a core material of a hard resin and then is injected between the molds. The mold inner space is formed in the mold, or a preformed core material is attached to a mold having a larger void than the core material to form the mold inner space.
The foam injection molding method according to 2 or 3.