JPH0729319B2 - Injection molding method and apparatus for foamed products - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a method and apparatus for injection molding foamed products.

(Prior Art) In the case of injection molding a foamed product, conventionally, for example, a suspension-polymerized vinyl chloride resin powder or pellets are heated and melted in a cylinder of an injection molding machine and foamed,
The foamed resin was injected from the nozzle into the mold for molding.

There is also a method in which the molten resin is filled in the mold and then foamed.

(Problems to be Solved by the Invention) However, in these methods, foaming occurs in the cylinder of the injection machine or in the mold, so that a special injection machine or mold is required.

Further, the control of foaming is complicated, and it is difficult to obtain a desired foamed product.

Furthermore, with the above raw materials, a foam layer forms up to the product surface,
The surface was rough and the appearance and feel were poor and the wear resistance was poor.

(Means for Solving Problems) The present invention has been made to solve the above problems,
The gist is that the raw material made of foamed plastisol is heated to below the foaming temperature in the cylinder part of the injection machine and gelled, and the gelled raw material is heated above the foaming temperature in the nozzle part of the injection machine to foam. Then, the foamed raw material is injected into the cavity of the mold to be cooled and solidified, thereby providing an injection molding method for a foamed product.

Another gist of the invention is to provide an injection molding machine having a cylinder portion and a nozzle portion, and a mold having a cavity connected to the nozzle portion of the injection molding machine, wherein the cylinder portion is filled with a foamed plastisol from a foaming temperature. A heating device that heats to a low temperature and gels is provided, and the nozzle portion has a first passage portion that is located on the cylinder portion side and has a tapered cross-sectional area that reduces the flow cross-sectional area. An injection molding device for a foamed product, comprising: a second passage portion that is heated to a foaming temperature or higher by frictional heat generated when passing the gelled raw material.

(Operation) In the method of the present invention, since foaming is performed in the nozzle portion, a general-purpose injection molding device can be used, and the equipment cost can be reduced. Further, foaming at the nozzle portion is easy to control, and a desired foamed product can be obtained.
Further, since plastisol having high fluidity is used as a raw material, the injection pressure is low, and a good cushion layer can be obtained without the bubbles in the raw material being crushed so much.
A skin layer having a smooth surface can be obtained on the surface side of the molded product.

In the device of the present invention, foaming can be reliably performed by raising the temperature of the raw material to the foaming temperature by frictional heat when passing through the second passage of the nozzle.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings from FIG. 1 to FIG. In FIGS. 1 and 2, reference numeral 1
Indicates an injection molding apparatus, and this injection molding apparatus 1 is an injection machine.
It has 10 and a mold 20.

The injection machine 10 includes a cylinder 11 (cylinder portion), a screw 12 inserted in the cylinder 11, a hopper 13 attached near the rear end of the cylinder 11, and a cylinder 4 arranged on the outer periphery of the cylinder 11. Pair of band heaters 14a, 14b, 14c, 14d
It has a (heating device) and a nozzle tip 15 (nozzle part) attached to the front end of the cylinder 11. The band heaters 14a, 14b, 14c and 14d are controlled independently of each other.

The passage 16 of the cylinder 11 has a gentle taper at the front end 16a.

As shown in FIG. 3, the nozzle tip 15 has a funnel shape and has a passage 17 along the axis. The passage 17 has a first passage portion 17a which is continuous with the front end portion 16a of the passage 16 and has a steeper taper than this, and a second passage portion 17b having a small diameter and which is continuous with the first passage portion 17a. . Although the second passage portion 17b has a gentle taper in the illustrated example, it may be straight. The average diameter of the second passage portion 17b is, for example, about 2 mm, and the passage 16 of the cylinder 11 is
It is very thin compared to the diameter (about 60 mm). Also, the second passage part
The length of 17b is about 3 to 7 cm.

The injection machine 10 is a general-purpose type used when injecting ordinary molten resin, only the nozzle tip 15 is specially made, and has a length about three times that of an ordinary short nozzle tip.

The mold 20 has a fixed plate 21 and a moving plate 22 that moves toward and away from the fixed mold 21 by a moving mechanism (not shown). A fixed die 23 and a movable die 24 are attached to the fixed plate 21 and the movable plate 22, respectively.

As shown in detail in FIGS. 4 to 6, the fixed mold 23 and the movable mold
Rectangle-shaped recesses 25 and 26 are formed on the opposing surfaces of 24, respectively, and when the fixed mold 23 and the movable mold 24 are closed, the recesses 25 and 26 form a cavity 27. . The molding surface 25a of the recess 25 of the fixed mold 23 is for molding the surface of the foamed product 40, which will be described later, and has a grain pattern as shown in FIG.

As shown in FIGS. 1 and 2, the fixed mold 23 has a sprue 28 communicating with the second passage portion 17b of the nozzle tip 15.
A gate 29 connected to the cavity 27 and a runner 30 connecting the sprue 28 and the gate 29 are formed.

As shown in FIG. 6, the movable die 24 is formed with a plurality of pin holes 31 whose one end is opened at the molding surface 26a near the peripheral edge of the recess 26, and the protruding pins 32 are housed in the pin holes 31. Has been done.

The foamed product 40 shown in FIG.
Injection molding.

First, as shown in FIG. 6, a plate-shaped core material 41 is attached to the molding surface 26a of the concave portion 26 of the movable die 24 using a double-sided tape or the like with the die 20 opened. As the core material 41, a gas permeable material such as a wood fiber board is preferable. In this state,
The pin hole 31 is closed by the core material 41, and a slight gap 45 is formed between the peripheral edge 41a of the core material 41 and the peripheral edge of the recess 26 (the peripheral edge of the cavity 27).

After the core material 41 is attached, the movable plate 22 is moved toward the fixed plate 21 and the movable mold 24 is applied to the fixed mold 23 to perform mold clamping.

On the other hand, the raw material (denoted by reference numeral 50 in the figure) is supplied from the hopper 13 to the cylinder 11. As a raw material, a low foaming type plastisol having a high fluidity (foaming ratio of about 3 times or less), for example, a plastisol obtained from a vinyl chloride resin paste, a plasticizer, a foaming agent, and minute hollow glass beads is used. The screw 12 is in the retracted position and rotates to feed the raw material toward the nozzle tip 15. The above raw material is cylinder 11
Band heaters 14a, 14b, 14c, 14 while passing through the passage 16 of
It is heated to d and gelled. Band heaters 14a, 14b, 14
The c and 14d are controlled so that the temperature gradually increases toward the nozzle tip 15. At the front end 16a of the passage 16 closest to the nozzle tip 15, the raw material is heated to a temperature slightly below the foaming temperature. When the temperature of the cylinder 11 is raised above the foaming temperature of the raw material, the raw material foams in the cylinder 11, and the injection amount is not constant in the general-purpose injector 10.

With the raw material filled in the cylinder 11 and reaching the middle of the passage 17 of the nozzle tip 15, the screw 12 advances and injects the amount of raw material corresponding to this advance stroke. As described above, the raw material is heated in the passage 16 of the cylinder 11 and gels to reach a temperature close to the foaming temperature immediately before the nozzle tip 15, and the flow passage cross-sectional area is rapidly reduced in the first passage 17a of the nozzle tip 15. It Then, when this raw material passes through the very narrow second passage portion 17b, frictional heat is generated and becomes equal to or higher than the foaming temperature. As a result, the raw material foams in the second passage portion 17b of the nozzle tip 15. Since the raw material has a high pressure, the bubbles are small.

The foamed raw material flows into the cavity 27 at a high speed through the sprue 28, the runner 30 and the gate 29 of the mold 20, where it is cooled and solidified to form the pad 42 of FIG. Note that it is difficult to accurately grasp the foaming phenomenon, but since the foaming raw material has a low pressure in the cavity 27, it can be presumed that foaming becomes active again and the bubbles become large. This foaming raw material also enters the gap 45 shown in FIG. 6 and is solidified there to form the end portion 42a of the pad 42. As a result, a foamed product 40 as shown in FIG. 7 is obtained.

After the injection molding, the movable die 24 is separated from the fixed die 23 and opened, and then the ejection pin 32 is operated to release the foamed product 40 from the movable die 24.

In the foamed product 40, a core material 41 and a pad 42 (foamed product) arranged on one surface of the core material 41 are laminated and integrated. Inside the pad 42, as shown in FIG. 9, the bubbles are smaller toward the surface, and the cushion layer 43 is relatively large and has a high expansion ratio, and the cushion layer 43 is relatively small and has a low expansion ratio or bubbles. And the skin layer 44 having no layer are continuously formed. The surface 44a of the skin layer 44 has a molding surface 2
By the transfer of 5a, a grain pattern as shown in FIG. 8 is added.

The thin edge portion 42a is integrally provided on the peripheral edge portion 41a of the core material 41, and it is not necessary to perform the terminal treatment.

Since plastisol is used as the starting material and the material contains fine glass beads, it has a high fluidity, and the foamed material does not remain in the passage 17 of the nozzle tip 15 or the runner 30, etc. The inside is smoothly filled and the narrow gap 45 is surely filled, so that a clean end portion 42a can be formed.

Further, since the raw material has high fluidity, the injection pressure can be low, the generated bubbles are not crushed so much, and a good cushion layer 43 can be obtained. Also, due to its high liquidity,
The surface 44a of the skin layer 44 can be made smooth.

At the time of injection, it passes through the core material 41 made of wood fiber board and the pin hole 31
Gas is degassed from the groove, and also from a groove (not shown) formed on the parting surface. Also,
The fine glass beads contribute to degassing the raw material. In this way, good degassing is achieved, so that a clean skin layer 44 on the surface 44a is obtained.

The composition of plastisol as a raw material was 100 parts by weight of PVC (vinyl chloride resin) paste obtained by emulsion polymerization,
8 DUP (diundecanol phthalate) as a plasticizer
5 parts, 6 parts by weight of Sn stabilizer, 5 parts by weight of Ba-Zn stabilizer, 2 parts by weight of ADCA foaming agent (azodicarboxylic acid amide), 2 parts by weight of Mg-Al lubricant, hollow glass 10 parts by weight of beads. The hollow glass beads are very fine and have a size of about 100 microns.

First, of the above plastisol compositions, the composition excluding glass beads was kneaded with a kneader and then degassed in vacuum to prepare a compound having an initial viscosity of 1500 cps. The above glass beads were added to this formulation to obtain a plastisol having a viscosity of 3000 cps.

A phenol resin-impregnated wood fiber board (thickness: 3 mm) was set as a base material in the mold 20, and the plastisol was introduced from the hopper 13.

Then, the temperatures of the respective portions A to D of the cylinder 11 are set to 140 ° C and 150 ° C.
Controlled at ℃, 160 ℃, 180 ℃, low injection pressure 80〜120Kg / cm ²
It fired at. The mold 20 is maintained at about 20 to 30 ° C., and the mold clamping force is 100 ton.

The temperature of the resin becomes 210 ° at the outlet of the nozzle tip 15, and the foaming temperature of 190 to 210 ° C (1
(The temperature at which foaming occurs in a second) and foams.

In the obtained molded product 40, the pad 42 has a two-layer structure of a cushion layer 43 having a thickness of 1.5 mm and a skin layer 44 having a thickness of 0.5 mm, and the surface 44a has a good appearance and feel, and a core material. The end portion 42a (thickness 0.5 mm) formed on the peripheral edge 41a of 41 was also clean. In addition, no pinholes, uneven coloring, jetting, flow marks, sharkskin, and weld lines were generated on the surface of the skin layer 44. In addition, neither the swelling of earthworms nor the phenomenon of two-stage foaming, which is often found in foam products, was observed.

The physical properties of the pad 42 are as follows: specific gravity 0.85, tensile strength 73Kg, elongation 225
%, The tear strength was 33.6 Kg / cm, and the average expansion ratio including the skin layer 44 and the cushion layer 43 was 1.8 times.

10 to 12 show an example in which the present invention is applied to the manufacture of an automobile door trim 60 (foamed product). The plate-shaped core material 61 made of a wood fiber board or the like has, for example, a peripheral edge portion 61a bent at 90 °, a step 61b is formed near the upper edge, and a convex portion 61c is formed slightly below the central portion. There is.

On the other hand, in the mold 70, the concave part 75 of the fixed mold 73 and the concave part of the movable mold 74.
The shape of the cavity 77 formed by 76 is substantially similar to the core material 61. Further, on the molding surface 75a of the recess 75 of the fixed die 73, a groove 78a having an annular shape and a groove 78b extending in the lateral direction are formed.
Are formed. Then, the core 61 is placed in the recess 75 of the movable mold 74.
A gap 65 is formed between the peripheral edge portion 61a of the core material 61 and the peripheral edge portion of the cavity 77 in the state of being attached to the molding surface 76a. In this state, the raw material foamed in the nozzle part of the injection machine passes through the runner 80 and the gate 79 in the same way as described above
By being injected into 77 and cooled and solidified in the cavity 77, the pad 62 is formed integrally with the core material 61, and the terminal portion 62a is formed in the gap portion 65.

Also in this example, the pad 62 has a continuous cushion layer 63 and skin layer 64. The door trim 60 is provided with a step 60b corresponding to the step 61b of the core material 61.
An armrest 60c is formed corresponding to the convex portion 61c. Further, the groove 78a of the fixed mold 23 allows the annular molding 60d to be formed.
(Projection) is formed, and the molding 60e extending laterally by the groove 78b.
Are formed.

A decorative cloth 60f such as a tricot is further welded to the door trim 60 by a high frequency welder. Pad 62
Since it has low foaming, it can be welded by high frequency.

The present invention is not limited to the above-mentioned embodiment and various modes are possible. For example, as shown in FIG. 7 and FIG.
42a may be extended to the back side of the core materials 41 and 61 and molded. The extensions are indicated by 42a 'and 62a' in the figure. In this case,
A gap is also formed between the back surface of the core material 41, 61 and the molding surface 26a, 76a of the movable die 24, 74.

The core material before injection may be held by vacuum suction. In addition to the wood fiber board, the core material may be a resin molded product or sheet metal.

The tapered first passage portion may be formed at the front end of the cylinder, and only the second passage portion having a small diameter and elongated shape may be formed in the nozzle tip. In this case, the nozzle portion is composed of the front end portion of the cylinder and the nozzle tip.

In the mold, for example, a fastener for attaching another component may be set in a fixed die, and the fastener may be integrally attached to the foamed product by injecting the foaming raw material.

Furthermore, the present invention can be applied to automobile interior parts such as armrests, instrument panels, sun visors, console boxes, handles, and seat covers, and foam products other than automobile interior parts, in addition to the door trims described above.

(Effects of the Invention) As described above, in the method of the present invention, a general-purpose injection molding device can be used, and the equipment cost can be reduced. Further, foaming at the nozzle portion is easy to control, and a desired foamed product can be obtained. Further, a good cushion layer and a skin layer having a smooth surface can be obtained.

In the device of the present invention, it is possible to surely perform foaming at the nozzle portion.

[Brief description of drawings]

The drawings from FIG. 1 to FIG. 9 show an embodiment of the present invention. FIG. 1 is a schematic sectional view of an injection molding apparatus before injection, and FIG. 2 is an injection molding apparatus after completion of injection. Schematic sectional view,
3 is an enlarged cross-sectional view of the nozzle tip, FIG. 4 is a front view of a fixed mold, FIG. 5 is a front view of a movable mold, FIG. 6 is a cross-sectional view of a mold main part in a mold open state, and FIG. Is a cross-sectional view of a foam product, No. 8
The figure is a front view of the foamed product, and FIG. 9 is an enlarged view of the skin layer and cushion layer of the foamed product. Fig. 10-Fig.
FIG. 12 shows another embodiment of the present invention. FIG. 10 is a sectional view of a door trim molding die, FIG. 11 is a sectional view of a molded door trim, and FIG. 12 is a front view of the door trim. is there. 1 ... Injection molding device, 10 ... Injection machine, 11 ... Cylinder (cylinder part), 12 ... Screw, 13 ... Hopper, 14
a, 14b, 14c, 14d …… Heating device (band heater), 15 ……
Nozzle part (nozzle tip), 16 ... Cylinder path,
17 ... Nozzle passage, 17a ... First passage portion, 17b ... Second passage portion, 20,70 ... Mold, 23,73 ... Fixed die, 24,74 ...
… Mobile type, 27,77 …… Cavity, 40,60… Foamed product,
41,61 …… Core material, 42,62 …… Pad layer, 43,63 …… Cushion layer, 45,65 …… Gap, 44,64 …… Skin layer, 50 …… Raw material.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29K 105: 06 (72) Inventor Mitsuaki Okada 3-15-14 Higashi Tateishi, Katsushika-ku, Tokyo Kobayashi Katsushika Corporation In-house (72) Makoto Shimada 3-15-14 Higashi-Tateishi, Katsushika-ku, Tokyo Kobayashi Katsushika Sales Office (72) Inventor Osamu Endo 3--15-14 East Tateishi, Katsushika-ku, Tokyo Kobayashi Katsushika Sales Co., Ltd. In-house

Claims (4)

[Claims] 1. A raw material comprising a foamed plastisol is heated in a cylinder portion of an injection machine to a temperature lower than the foaming temperature to be gelled, and the gelled raw material is heated to a temperature higher than the foaming temperature in a nozzle portion of the injection machine. An injection molding method for a foamed product, which comprises foaming and injecting the foamed raw material into a cavity of a mold to cool and solidify. 2. The gelled raw material is heated to a foaming temperature or higher by frictional heat when passing through a nozzle portion of an injection machine,
The injection molding method for a foamed product according to claim 1, wherein foaming is thereby performed in the nozzle portion. 3. The method for injection molding a foamed product according to claim 1, wherein the foamable plastisol is obtained from a vinyl chloride resin paste, a plasticizer, a foaming agent, and minute hollow glass beads. . 4. An injection molding machine having a cylinder portion and a nozzle portion, and a mold having a cavity continuous with the nozzle portion of the injection molding machine, wherein the cylinder portion is filled with a foamed plastisol at a temperature lower than a foaming temperature. A heating device that heats and gels is provided, and the nozzle portion is formed on the cylinder portion side and has a tapered first passage portion such that the flow cross-sectional area is reduced, and is formed with a small diameter and is long and gelled. An injection molding apparatus for a foamed product, comprising: a second passage portion that is heated to a foaming temperature or higher by frictional heat generated when passing a raw material.