JP3118125B2 - Foam injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle interior panel (instrument panel, door panel, seat back panel, steering wheel, handle, etc.), furniture (seat portion of a chair, etc.), miscellaneous goods (shoes, slippers, etc.). Foam injection molding in which a skin layer on the surface and an internal foam layer are formed as described above, and a foam molded article in which a foam layer and a skin layer are formed on one surface of a core material of a hard resin as necessary is obtained by an injection molding machine. More particularly, the present invention relates to a method for controlling a foaming state of a foamable resin to obtain a molded article having a desired feel and a good surface.

[0002]

2. Description of the Related Art Conventionally, this foam injection molding method includes:
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 mold is opened to expand the space to foam the resin, and the cooled and solidified skin on the mold surface side This is a method for obtaining a foam molded article having a layer and a foam layer inside a mold. In this method, a circuit configuration capable of changing the mold opening speed for each injection by providing a flow rate adjusting valve in the mold opening hydraulic circuit is disclosed, but it is suggested which mold opening speed is appropriate. It does not do.

In recent years, attempts have been made to apply this foam injection molding method to the above-described molding of automobile interior panels. This is because the resin yield is higher than that in which the skin layer is separately formed by a vacuum forming method or the like, and the skin layer can be formed in a continuous process.

[0004] In particular, automobile interior panels are required to have a soft and soft feel on the surface. In order to obtain this feeling, the selection of materials is also important. A thermoplastic elastomer having rubber-like elasticity at room temperature, plasticized at high temperature and capable of injection molding is used as a material for forming the skin layer and the foam layer. Attempted use (unpublished)

[0005]

However, when the conventional foam injection molding method is applied to molding of a thermoplastic elastomer or the like, the foaming ratio is too low and the skin layer is too thick, or the foaming ratio is too high and the skin layer is too thin. In addition, there was a problem that the surface transferability of the skin layer was poor due to poor grain transferability, and that the skin layer could not be stably obtained at an appropriate expansion ratio with good grain transferability. In JP-A-48-22164 and JP-A-49-10967, it is conceptually known to control the expansion ratio, that is, the thickness of the skin layer, by controlling the time from the completion of injection to the start of mold opening. However, time control alone is not sufficient.

Accordingly, the present invention has been made based on the knowledge obtained during a number of experiments, and it is an object of the present invention to provide a foaming method which can ensure an appropriate expansion ratio and has excellent transferability. It is an object of the present invention to provide a foam injection molding method capable of obtaining a molded product.

[0007]

According to the foam injection molding method for solving the above-mentioned object, a resin containing a foaming agent is injected into a space in a mold which is held openably, and then the mold is opened. In a foam injection molding method of expanding a space to foam a resin and obtaining a foam molded product having a cooled and solidified skin layer on the mold surface side and a foam layer inside the mold, the resin is an elastomer, Set the mold opening speed after starting mold opening to 0.
5 to 10 mm / sec, the foaming ratio of the foamed layer is 1.2 times or more, the time from the completion of injection to the start of mold opening is 4 seconds or less, and the foaming ratio of the foamed layer is 1.6 times or more. Or the mold surface temperature is from room temperature to 60
° C.

Here, the elastomer is preferably a saturated styrene elastomer. In particular, the average molecular weight based on the GPC method is more than 30,000 and 70,000 or less,
SK6301: Hardness based on type A exceeds 50 and is 100
The following saturated styrenic elastomer, or a compound of this saturated styrenic elastomer and polyolefin, JIS K6301 of this compound: A
The hardness based on the mold is in the range of more than 50 to 100 or less, and the melt viscosity of the compound at the injection temperature is 1
Those having a range of 300 poise to 3,000 poise at a shear rate of 000 / sec and a range of 5,000 poise to 50,000 poise at a shear rate of 10 / sec are preferred because they have excellent heat deformability and weather resistance.
The foaming agent may be any one that can foam the elastomer by injection molding, and a decomposable foaming agent such as an inorganic compound such as sodium bicarbonate or an organic compound such as an azo compound is used.

[0009]

[Effect] In the case of an elastomer foam molded article, the expansion ratio is controlled to be about 1.2 to 2 times. However, when the mold opening speed after the start of mold opening is less than 0.5 mm / sec, the mold opening speed becomes lower. Is too slow compared to the cooling rate of the above, the skin layer becomes thick and the foam layer is extremely thin.
Can not be obtained. On the other hand, if the mold opening speed exceeds 10 mm / sec, the skin layer becomes extremely thin and the cell structure of the foam becomes non-uniform. At the same time, the skin layer cannot follow the opening speed of the mold, resulting in poor transferability.

[0010] Similarly, in the case of an elastomer foam molded article, the preferable expansion ratio is as high as about 1.6 to 2 times. However, if the time from the completion of injection to the start of mold opening exceeds 4 sec, the cooling of the resin in the mold becomes impossible. As the skin layer becomes thicker, the foam layer becomes extremely thin and approaches a non-foamed molded product.
In order to secure the expansion ratio of 1.6 to 2 times, in addition to the limitation of the mold opening speed, the time from the completion of injection to the start of mold opening is preferably shortened to 0.3 to 0.5 sec.

[0011] Similarly, in the case of foaming molded articles made of an elastomer, it has been found that a difference in mold surface temperature is the cause when pursuing a difference in quality between molding in summer and molding in winter. That is, if the mold surface temperature exceeds 60 ° C., the surface flaps. If the mold temperature is lower than normal temperature, a desired expansion ratio cannot be obtained even under the above conditions. Therefore, in addition to the limitation of the mold opening speed, the mold surface temperature is preferably controlled to 35 to 45 ° C.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, referring to FIG. 5, a molding machine to which the foam injection molding method of the present invention is applied will be described with reference to FIG. 5, and then the foam injection molding method will be described with reference to FIGS.

In FIG. 5, spaces A and B are fixed to a pair of fixed plate 1 and movable plate 2 facing each other so as to be openable and closable, and a resin containing a foaming agent is injected. D is formed. Also, after the resin containing the foaming agent is injected from the known injection device C, the distance between the molds A and B is opened by the stroke l, so that the space D for allowing internal foaming can be expanded. I have. Therefore, a cylinder device 3 is provided on the fixed platen 1, a thrust rod 6 is connected to the extension rod 5 via a micrometer head 7, and the rod 6 is fixed to the movable platen 2 with a nut 9 a. Further, in order to withstand the injection pressure of the injection device C, the pressing 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 injection is completed decreases,
The dies A and B are opened by the cylinder device 3 below the pressing force of the cylinder device 3 to expand the space D described above.

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

Next, a foam injection molding method based on a specific experiment will be described below. As a styrene-based thermoplastic elastomer component, an average molecular weight of 50,000 based on the GPC method,
JIS K6301: A type obtained by adding 4% by weight of an azodicarbonamide-based blowing agent to a saturated styrene-butadiene-based elastomer having a hardness of 67 based on type A and a styrene content of 20% by weight. And the mold temperature is 40 ° C
And foam moldings were obtained at various mold opening speeds.

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. In FIG. 1, when the mold opening speed after the mold opening is started is low, the expansion ratio is low,
When the mold opening speed is high, the expansion ratio is high. FIG.
As shown in (a), if the mold opening speed is less than 0.5 mm / sec, the mold opening speed is too slow compared to the cooling speed of the resin, so that the skin layer a becomes thick and the foamed layer b becomes extremely Thinner. In addition, as shown in FIG.
If it exceeds mm / sec, the skin layer a is extremely thin, the skin layer a cannot follow the opening speed of the mold, and the foam cells c in the foam layer b are irregular. However, as shown in FIG. 2B, the mold opening speed is 0.5 to 10 mm /
sec, the skin layer a and the foam layer b are balanced, the surface condition of the skin layer a is good, and the foam cell c
Is also uniform.

Further, the relationship between the time from the completion of injection to the start of mold opening and the expansion ratio will be described with reference to FIGS. In FIG. 3, when the mold opening speed is 5 mm / sec and the mold opening start time is short, the expansion ratio is high, and the skin layer thickness and hardness are low. Conversely, if the mold opening start time is late, the foaming ratio is low, and the skin layer thickness and hardness are high. In order to make the expansion ratio 1.6 times or more, the mold opening time must be within 4 seconds. In order to obtain a more preferable high foaming ratio (around 2 times) and to obtain good grain transfer and no gloss unevenness, the mold opening start time is 0.3 to
It must be 0.5 seconds. As shown in FIG.
If the mold opening start time is 0.3 seconds, the thickness of the foamed molded product becomes 2A, which is twice as large as the original in-mold distance A, and the foaming ratio becomes about twice, giving a soft touch. Can be.
However, if the time is less than 0.3 seconds, the skin layer surface becomes glossy due to friction with the mold surface when the mold is opened. Also,
As shown in FIG. 4B, when the mold opening start time reaches 1.0 second, the skin layer a becomes thicker and the foaming ratio decreases. Further, as shown in FIG. 4 (c), when the mold opening start time is 4 seconds, the skin layer a is further thickened, but the thickness is 1.6A and the expansion ratio is within the allowable range of 1.6. .

In the above description of the embodiment, the foam injection molding method for a foam molded article in which both sides of the foam layer are skin layers has been described, but the foam layer and the skin layer are formed on a resin core material. This foam injection molding method can be applied to a laminate such as an instrument panel.

A molding machine for obtaining such a laminate in a series of steps will be described with reference to FIG. In FIG. 6, this molding machine has a skeleton including a bed 101, a crown 102, and a stand frame 103.
A bolster 10 on which two lower dies, that is, a first lower die 105 and a second lower die 106, are mounted on the upper part 1 is provided.

The bolster 107 can be moved in parallel by a driving device (not shown). The first position shown by a solid line where the first lower die 105 is the center position of the molding machine, and the second lower die 106 is the center position of the molding machine. And the second position shown by the two-dot chain line. An elevating cylinder 111 and an adjusting cylinder 112 are fixedly mounted on the crown 102. Slides 1 are attached to ends of the piston rods 111 a and 112 a of the elevating cylinder 111 and the adjusting cylinder 112.
14 is fixed. An upper die 115 is attached to the slide 114. By operating the elevating cylinder 111, the upper die 115 is moved to the lower die 105,
It can move up and down toward 106. By operating the adjustment cylinder 112, the upper mold 115
Is slightly movable up and down toward the lower molds 105 and 106. At four corners of the bed 101, equilibrium support devices 118 are provided, and the slides 114 are supported equilibrium with respect to the bed 101 by the equilibrium support devices 118. Further, a first lower mold 1 is provided on a side of the molding machine.
05, a first injection unit and a second injection unit (not shown) for supplying a molding material to the second lower mold 106 are provided.

Next, a method for manufacturing a laminate using the molding machine having the above-described structure will be described with reference to FIG. FIG. 7 (a)
As shown in (2), the bolster 107 is moved to the second position, the piston rod 111a of the elevating cylinder 111 is extended to lower the upper mold 115 toward the second lower mold 106, and the upper mold 115 and the The second cavity 125 is formed with the second lower mold 106. Then, as shown in FIG. 7B, a core material of a thermoplastic resin is supplied to the second cavity 125 from a second injection unit (not shown).
Is molded. When the molding is completed, as shown in FIG. 2C, the piston rod 111a of the elevating cylinder 111 is left while the molded core material 126 is left in the upper mold 115.
And the upper mold 115 is raised, and the bolster 107
Is moved to the first position.

Then, as shown in FIG. 8A, the upper mold 115 in which the piston rod 111a of the lifting cylinder 111 is extended and the core material 126 is mounted is moved to the first lower mold 1
05, and the core material 126 and the first lower mold 10
5, the first cavity 128 is formed. And FIG.
As shown in (b), a foam material 1 such as a styrene elastomer containing a foaming agent described above 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.
The upper die 115 is raised by a predetermined stroke t by shortening the piston rod 112a of the first cavity 12a.
When the volume of the foaming material 8 is increased, the pressure of the foaming material 130 decreases to become equal to or lower than the foaming critical pressure, and foaming occurs inside the foaming material 130 to form the foamed layer 132. In addition, the foam material 130 at the portion in contact with the first lower mold 105 is cooled and solidified in an unfoamed state, and the hard skin layer 13 without foaming is formed.
3 is formed. And, in this way, the core material 126
When the foam layer 132 and the skin layer 133 are integrally laminated and formed thereon, the piston rod 11 of the elevating cylinder 111
1a is shortened, the upper mold 115 is raised, and the core 126
The laminate including the foam layer 132 and the skin layer 133 is taken out, and one cycle of molding is completed.

As described above, the foam material 130 is filled and foamed between the core material 126 and the first lower mold 105 while the core material 126 is left in the upper mold 115 in which the core material 126 is formed. First cavity 12 of variable volume for cooling and solidification
8 is formed, and the foam layer 132 and the skin layer 133 are integrally laminated and formed on the core material 126. Therefore, a laminate including the core material 126, the foam layer 132, and the skin layer 133 is formed into one molding machine. , It is possible to manufacture continuously, and the number of man-hours can be greatly reduced. Also, the core material 12
Since 6 is molded from the molding material, there is almost no material loss,
Yield is greatly improved. For this reason, the method is optimal as a method for manufacturing a laminate having a large and complicated shape such as an interior panel of an automobile or the like, particularly, an instrument panel of an automobile. Further, when the core material and the foamed material are made of the same material, the adhesion between the core material and the foamed layer is improved, and the material can be recycled.

The above-mentioned core member 126 is formed by injection molding using one of the molds (two-layer molding and mold space expansion method).
However, a space is formed by mounting a core material that has been injection-molded in advance in a mold that can be opened (insert,
Mold space expansion method).

[0025]

According to the foam injection molding method of the present invention, for an elastomer containing a foaming agent (preferably a styrene-based thermoplastic elastomer), the mold opening speed after the start of mold opening is set to an appropriate range, and the injection is performed. When the time from the completion to the start of mold opening or the mold surface temperature is set to an optimal condition, the foamed molded article has a high foaming ratio of 1.6 to 2 times and an excellent surface condition, and is applied to a panel for an automobile interior. Can open applicability.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a mold opening speed and an expansion ratio.

FIG. 2 is a cross-sectional view showing a change of a foam molded product according to a mold opening speed.

FIG. 3 is a graph showing a relationship between a mold opening start time and an expansion ratio.

FIG. 4 is a cross-sectional view showing a change of a foam molded product according to a mold opening start time.

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

FIG. 6 is a schematic view of another molding machine to which the foam injection molding method of the present invention is applied.

FIG. 7 is a view showing a molding step by another molding machine.

FIG. 8 is a view showing a molding step by another molding machine.

[Explanation of symbols]

 A, B Mold C space a Skin layer b Foam layer

────────────────────────────────────────────────── ─── Continuing on the front page (51) Int.Cl. ⁷ Identification code FIB29L 9:00 31:44 31:50 31:58 (72) Inventor Hiroaki Kondo 2-3-1 Shinhama, Araimachi, Takasago City, Hyogo Prefecture Inside Kobe Steel, Ltd. Takasago Works (72) Inventor Masahiko Kashiwa 2-3-1, Shinama, Araimachi, Takasago City, Hyogo Prefecture Inside Kobe Steel Works, Takasago Works (72) Inventor Takeshi Nagaoka 2-chome, Araimachi, Takasago City, Hyogo Prefecture No.3-1 Kobe Steel, Ltd. Takasago Works (72) Inventor Masayoshi Ueda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Naoki Murase 1 Toyota City Toyota Town, Aichi Prefecture Toyota Motor Inside Motor Vehicles Co., Ltd. (72) Inventor Keiichi Hasegawa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Ryoichi Ito Yokkaichi, Mie Prefecture No. 1, Toho-cho, Mitsubishi-Yoka Co., Ltd. Yokkaichi Research Institute (72) Inventor Izumi Ishii No. 1, Toho-cho, Yokkaichi-shi, Mie Pref. Asahi Kasei Kogyo Co., Ltd. (7-1) 1-31, Yoko, Kawasaki-ku, Kawasaki-shi (72) Inventor Shoichi Kanno 1-3-1, Yakko, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Asahi Kasei Kogyo Co., Ltd. 50-103568 (JP, A) JP-A-5-139447 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. After injecting an elastomer containing a foaming agent into a space in a mold that is held openably , the mold is opened to expand the space and foam the elastomer. in the cooling solidified foam injection molding process for obtaining a foam molded article having a skin layer and the mold inner foam layer
Therefore, the expansion ratio of the foam layer is 1.2 times or more.
As described above, the elastomer is cooled and solidified in an unfoamed state.
Foam injection molding process, characterized in that sets the mold temperature in the mold surface temperature, the mold opening speed after mold opening start and 0.5 to 10 mm / sec. 2. In a space in a mold which is held openably.
After injecting the elastomer containing the foaming agent, open the mold.
And expanding the space to expand the elastomer.
And the cooled and solidified skin layer on the mold surface side
A foam injection molding method for obtaining a foam molded article having a foam layer
The time from the completion of injection to the start of mold opening is set within 4 seconds, and the mold opening speed after the start of mold opening is 0.5 to 10 mm / s.
ec, and the expansion ratio of the expanded layer is 1.6 times or more. 3. The foam injection molding method according to claim 1, wherein the mold surface temperature is 35 ° C. to 60 ° C.