JPH10146869A - Injection molding machine and thermoplastic synthetic resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the injection molding of a thin-walled and/or deep container-shaped molded product by a compact injection molding machine. SOLUTION: An injection molding machine 11 is constituted so that a plunger 13 being an extruder is fitted in the accumulator 12 connected to a mold 14 in a freely slidable manner and the shape of the leading end part 22 of the plunger 13 is fitted to the pointed shape of the leading end part 15 of the accumulator 12. By this injection molding machine, a thin-walled and/or deep container-shaped molded product wherein the ratio L/t of the raw material max. flow distance L in the mold 14 to the wall thickness (t) of the molded product becomes 200 or more is molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine and a thermoplastic synthetic resin molded article molded using the injection molding machine.

[0002]

BACKGROUND OF THE INVENTION When molding a thin molded product or a deep container molded product, it is necessary to perform injection molding with a long material flow distance in a narrow cavity of a mold. Molding generally requires high injection pressures. In particular, when injection molding a large molded product that uses a large amount of molding material, a large injection molding pressure of 1000 kgf / cm ² or more is required. Injection molding of a molded product requires a large-capacity large-sized extruder and an expensive injection molding machine equipped with a high-strength mold. Further, in the injection molding using such a high injection pressure, there is a residual stress in the molded product, and deformation such as warping or waving based on the residual stress is likely to occur. Further, when the injection direction of the raw material is set to the height (depth) of the molded article, and when molding a molded article having a deep container shape, the core mold (male mold) of the mold tends to fall down due to the high injection molding pressure. There is also a problem to say.

[0003]

2. Description of the Related Art As means for reducing the size of the large-sized injection molding machine, a raw material melt extruded from an extruder is temporarily stored in an accumulator, and the raw material melt is molded from the accumulator by a plunger. Is provided. More recently, for example, as shown in FIG. 4, an injection molding machine (1) having both an extruder and a plunger has been provided. In the injection molding machine (1) shown in FIG. 4, (2) is a cylinder, a raw material inlet (3) is provided at the root end, and (4) is a screw, which is provided in the cylinder (2). It is mounted so that it can slide in the axial direction, and a mold is inserted into the discharge port (5) of the cylinder (2).
(6) is concatenated.

[0004] In the injection molding machine (1) having the above structure, the raw material is charged into the cylinder (2) from the charging port (3), and the screw (4) is rotated and heated in the cylinder (2). In this way, the raw material is melted and kneaded, sent to the tip of the cylinder (2), and the screw (4) is retracted.The molten material is stored at the tip of the cylinder (2), and a predetermined storage amount is obtained. Then, the screw (4) is advanced by a driving device (not shown) to inject the raw material melt into the mold (6) from the discharge port (5) of the cylinder (2). In such an injection molding machine (1), the screw (4) also serves as a plunger, and the structure can be made compact.

[0005]

However, in the above-mentioned injection molding machine (1), the screw (4) is retracted to store the raw material melt at the tip of the cylinder (2). As the material recedes, the raw material processing zone becomes shorter, the kneading and melting state of the raw material stored at the tip of the cylinder (2) tends to be uneven, and the injection molding pressure is lower than that of the conventional injection molding machine (1). There is no guarantee that it can be made much lower than this, and such unevenness in the kneading and melting state, coupled with the fact that the injection molding pressure cannot be made too low, also causes deformation such as warpage and waving of the molded product. . Further, since the raw material melt remains in the cylinder (2) after the injection molding, an accurate injection amount cannot be obtained, and there is a problem that the raw material melt is burned in the cylinder (2).

[0006]

According to the present invention, as a means for solving the above-mentioned conventional problems, a die (1) is provided at a tip discharge port (16).
Accumulator (12) that the gate (26) of 4) is in contact with
And a plunger (13) slidably fitted to the accumulator (12), and the plunger (13)
Is a cylinder (17) having a tip bulge (19) and a raw material inlet (18) at the root end, and a screw (20) rotatably mounted in the cylinder (17). The tip of the screw (20) comes out of the tip of the cylinder (17), and the tip outside portion (21) of the screw (20) and the tip bulging portion (19) of the cylinder (17) Plunger tip
(22) is an accumulator (12) tip (15) is an injection molding machine (11) having a pointed shape that fits the inner shape,
An injection molding machine (11) in which the ratio L / t of the maximum flow distance L of the raw material in the mold (14) to the thickness t of the molded article to be molded is set to be 200 or more. It is.
According to the injection molding machine (11), the molded product is 50 to 700 k.
Injection molding can be performed with a molding pressure of gf / cm ² , and the material injection direction is height H. The height H is 500 mm or more, and the ratio W / H between the maximum diameter W and the height H is 1 0.4 or less, and in particular, a molded article in the shape of a square deep container can be easily molded. A preferable thermoplastic synthetic resin used for the molded article is an olefin resin having an MFR of 20 or more and 200 or less.

[0007]

1 to 3 show an embodiment of an injection molding machine (11) used in the present invention. The injection molding machine (11)
Is the accumulator (12) and the accumulator (1
2) a plunger (13) slidably inserted in the axial direction by a drive source (not shown), and a mold (14) connected to the tip of the accumulator (12). The inside of the tip (15) of the radiator (12) has a pointed shape, the tip is provided with a discharge port (16), and the plunger (13) has a raw material inlet (18) at the root end. ) And a cylinder (17) having a tip bulge (19), and the cylinder (1
7) a screw (20) rotatably mounted by a driving device (not shown) inside, and the tip of the screw (20) goes out from the tip of the cylinder (17) and goes out of the tip.
(21), and the plunger tip (22) composed of the tip protrusion (21) and the tip bulge (19) of the cylinder (17) is connected to the tip (15) of the accumulator (12). ) Has a pointed shape conforming to the pointed shape inside, and a gap (2) between the inner periphery of the accumulator (12) and the plunger tip (22).
3) is preferably set to 0.03 to 0.5 mm, and the capacity of the accumulator (12) and the extrusion capacity of the plunger (13) (filled between the cylinder (17) and the screw (20)) It is preferable to set the ratio to 2: 1 to 10: 1.

If the gap (23) is set to 0.03 to 0.5 mm, the raw material melt (34) slightly enters the gap (23) and acts as a lubricant to cause the plunger. The operation of (13) becomes smooth. However, if the gap (23) is less than 0.03 mm, it is difficult for the raw material melt (34) to enter the gap (23) smoothly, and the raw material melt (34) may be seized. If the gap (23) exceeds 0.5 mm, the accumulator (12)
The residual amount of the raw material melt (34) in the inside increases or the gap (23)
This causes a problem that the raw material melt (34) may leak.

If the ratio of the extrusion capacity of the plunger (13) to the capacity of the accumulator (12) is 1: 2 or more, the effect of obtaining a large volume molded product by the accumulator (12) is remarkable. However, if the ratio exceeds 1:10, the storage time of the raw material melt (34) in the accumulator (12) becomes long, and the raw material melt (34) may become non-uniform. There is a risk of uniformity. When the ratio between the extrusion capacity of the plunger (13) and the capacity of the accumulator (12) is in the range of 1: 2 to 1:10, the temperature distribution and the molten state of the raw material melt (34) are uniform. , And the fluidity is stabilized, so that a low injection pressure can be applied.
Further, in the injection molding machine (11) of the present invention, the diameter of the discharge port (16) of the accumulator (12) and the gate (26) of the mold (14) is set to 3 to 3 times the nozzle diameter of a normal injection molding machine. The flow resistance of the raw material melt (34) in the nozzle part is reduced by setting the diameter to 10 times, and the injection pressure of the raw material melt (34) stored in the accumulator (12) is reduced in as short a time as possible. For example, it is desirable to inject at an injection pressure of 80% or less of the injection pressure of the in-line type injection molding machine (1) shown in FIG.

The mold (14) is composed of a fixed mold plate (24) and a movable mold plate (25), and the gate (26) of the fixed mold plate (24) is provided with an accumulator (12). The sprue (28) is interposed between the cavity (27) of the mold (14) and the gate (26). Further, a hot water pipe (29, 30) for heating is disposed on the fixed mold plate (24) and the movable mold plate (25), and if necessary, the fixed mold plate (24) and the movable mold plate are movable. A high-frequency induction heating type peripheral instantaneous heating device (31, 32) may be arranged near the mold surface of the mold plate (25), that is, in the vicinity of the peripheral surface of the cavity (27).

The thermoplastic synthetic resin used in the present invention comprises:
Primarily polyethylene, polypropylene, olefinic resins such as polypropylene synthesized with a metallocene catalyst, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, etc., but other polyvinyl chloride, polyamide, polystyrene, polymethyl methacrylate, polyacetal , Polybutene, polycarbonate, polyethylene terephthalate, polyether sulfone, polytetrafluoroethylene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, styrene-butadiene-styrene block copolymer, styrene-
Ethylene-butylene-styrene block copolymer, acrylonitrile-styrene copolymer, acrylonitrile-
Butadiene-styrene copolymer, acrylonitrile-acrylic rubber-styrene copolymer, acrylonitrile-E
PDM-styrene copolymer, acrylonitrile-chlorinated polyethylene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, styrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyvinyl chloride-based Thermoplastic elastomer, polyamide-based thermoplastic elastomer, polybutadiene-based thermoplastic elastomer,
Polyurethane thermoplastic elastomer, styrene butadiene rubber, butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, isobutylene-isoprene rubber, etc. may be used, and these may be a mixture of two or more. Good. Also, a new synthetic resin or a recycled synthetic resin can be used. Preferably, the MFR value is 20.
A thermoplastic synthetic resin excellent in fluidity of 30 to 200, preferably 30 to 200 is selected. MFR value is 20
If it exceeds 0, the impact resistance of the molded product becomes poor.

In the present invention, an inorganic filler may be added to the thermoplastic synthetic resin in an amount of 50% by weight or less. Examples of the inorganic filler include glass fiber, carbon fiber, ceramic fiber, rock wool. , Inorganic fibers such as metal fibers, carbon black, calcium carbonate, talc,
There are clay, kaolin, mica, alumina, aluminum hydroxide, silicic acid, silicate, various cements, fly ash, sludge incineration ash and the like. When inorganic fibers are used as the inorganic filler, the aspect ratio (fiber length / fiber diameter) of the inorganic fibers is 30 or more, and the fiber length is 0.1 to It is desirable to select one within a range of 10 mm.

In addition to the above components, the raw materials further include, for example, lead white,
Lead salts such as tribasic lead sulfate and dibasic lead phosphite, lead stearate, barium stearate, metal soaps such as barium ricinoleate, organic tin compounds such as dibutyltin maleate and dibutyltin mercaptide, Nonmetallic stabilizers such as epoxy compounds, antioxidants such as phenolic compounds and organic phosphite compounds, ultraviolet absorbers such as benzophenones and benzotriazoles, antioxidants, and plasticizers such as phthalate esters Agents, pigments such as titanium white, chrome yellow, navy blue, carbon black and red iron, coloring agents, fatty acid waxes, lubricants such as metal soap, antistatic agents such as surfactants, impact enhancers, etc. Is also good. In particular, the use of suitable heat stabilizers is required.

In the injection molding machine (11), the molding material (3
3) from the raw material charging port (18), the molding raw material (33) is rotated by rotating the screw (20) of the plunger (13) and heating means (not shown) to convert the molding raw material (33) into the cylinder (17).
The mixture is melted and kneaded, and the plunger (13) is retracted. The raw material melt (34) is charged into an accumulator as shown in FIG.
Store in (12). When a predetermined amount of the raw material melt (34) is stored in the accumulator (12), the fixed mold plate (24) and the movable mold plate (25) of the mold (14) are separated as shown in FIG. The mold (14) is heated to a predetermined temperature by the hot water pipes (29, 30). Then, the rotation of the screw (20) of the plunger (13) is stopped to advance the plunger (13), and the gate (2) of the mold (14) is discharged from the discharge port (16) of the accumulator (12).
The raw material melt (34) is injected into the cavity (27) through 6) and the sprue (28). Injection molding at this time is usually 5
0 to 700 kgf / cm ^2, and if desired, only the vicinity of the peripheral surface of the cavity (27) of the mold (14) is heated to a predetermined temperature in the range of 100 to 200 ° C. by the heating device (31, 32). You may.

In the above-mentioned injection molding, if desired, the fixed side mold plate (24) and the movable side mold plate (25) of the mold (14) are slightly opened in the initial state, so that the inside of the cavity (27) is opened. The gas (air) is discharged, and then the fixed-side template (24) and the movable-side template (2) are discharged.
Injection compression molding may be performed with 5) completely closed.

Example 1 An injection molding machine (11) having a mold clamping pressure of 650 tons is used, and a molding raw material (33) having the following composition is used. 100 parts by weight of polypropylene (MFR value: 50) 100 parts by weight of stabilizer 0.5 parts by weight of pigment 2 parts by weight The above molding material was melted and kneaded by heating to 230 ° C. in a plunger (13). For injection molding, use a hot water pipe (29,3
0) to heat the mold (14) to 50 ° C., and immediately before injecting the raw material melt (34), the heating device (31, 32) heats the vicinity of the peripheral surface of the cavity (27) by 180 ° C. for 5 seconds. Heat to The time (filling time) for filling the raw material melt (34) from the plunger (13) into the accumulator (12) is 0.5.
Min, raw material melt from accumulator (12) to mold (14)
The injection time of (34) is 0.2 minutes and the injection pressure is 600 kgf /
cm ² was set. By the above injection molding, length 540mm, width 480mm, height 790mm, thickness 3.5mm, weight 4.6kg
Was manufactured in a 2 minute cycle. The maximum flow distance L in the injection molding machine (11) is 1050 mm,
L / t is 300. The molded article is homogeneous, has good surface properties, and has excellent appearance without deformation.

Comparative Example A conventional injection molding machine shown in FIG.
Injection molding of the same molded article as in Example 1 by (1) required an injection molding machine equivalent to a mold clamping pressure of 1600 tons and an injection pressure of about 1000 kgf / cm ² . However, at such a high injection molding pressure, wavy deformation was observed on the bottom surface of the molded product.

Example 2 A molding raw material (33) having the following composition is used. Low-density polyethylene (MFR value 100) 100 parts by weight Fly ash 50 parts by weight Stabilizer 0.5 part by weight Pigment 2 parts by weight The above molding material was melted and kneaded by heating to 180 ° C. in a plunger (13). The heating condition of the mold (14) was 30 ° C., and the heating condition of the peripheral surface of the cavity (27) was 120 ° C. for 3 seconds.
In the present embodiment, the fixed side mold plate (2
A gap of 5 mm was provided between 4) and the movable mold plate (25), and the mold (14) was started to be closed 5 seconds after the start of injection and completely closed in 5 seconds. In this embodiment, the charging time to the accumulator (12) is 0.6 minutes, the injection time is 0.2 minutes, and the injection pressure is 550 k.
gf / cm ² , and a deep container-shaped molded product having the same homogeneity and good surface properties as in Example 1 and having an excellent appearance without deformation was obtained.

[0019]

According to the present invention, a large, thin and / or deep container-shaped molded product can be injection-molded with low injection pressure by a compact and inexpensive injection molding machine with high productivity, and the molded product obtained by the present invention can be obtained. Is homogeneous and has good surface properties,
In addition, it has an excellent appearance without deformation.

[Brief description of the drawings]

 1 to 3 show an embodiment of the present invention.

FIG. 1 is a schematic cross-sectional view showing a state when storage in an accumulator is started.

FIG. 2 is a schematic sectional view showing a state when storage in an accumulator is completed.

FIG. 3 is a schematic sectional view showing an injection molding state.

FIG. 4 is a schematic sectional view of a conventional example.

[Explanation of symbols]

 11 Injection molding machine 12 Accumulator 13 Plunger (extruder) 14 Die 15 Tip 16 Discharge port 17 Cylinder 18 Material inlet 19 Tip bulging part 20 Screw 21 Tip outside part 34 Material melt

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kunihiko Sato, 74 Aron Kasei Co., Ltd. Technical Research Laboratory at 1 Funamicho, Minato-ku, Nagoya-shi, Aichi (72) Inventor Shigeru Matsuzaka 1 Funamicho, Minato-ku, Nagoya-shi, Aichi At 74 Aron Kasei Co., Ltd.

Claims (5)

[Claims] 1. An accumulator having a mold gate connected to a tip discharge port, and a plunger slidably fitted to the accumulator, wherein the plunger has a tip bulging portion. A cylinder provided with a raw material inlet at a root end thereof, and a screw rotatably mounted in the cylinder. The tip of the screw comes out of the tip of the cylinder, and the tip of the screw The tip of the plunger, which is composed of an outside portion and a swelling portion of the tip of the cylinder, is an injection molding machine having a pointed shape adapted to the inside shape of the accumulator tip, and the maximum flow distance of the raw material in the mold. An injection molding machine characterized in that a ratio L / t between L and a thickness t of a molded product to be molded is set to 200 or more. 2. A molded article formed by the injection molding machine according to claim 1, wherein the molded article is 50 to 700 kgf /
Thermoplastic synthetic resin molded product characterized by being injection molded with a molding pressure of cm ² 3. A molded article according to claim 2, wherein said molded article is in the shape of a deep container and has a height H in a raw material injection direction, said height H being 500 mm or more, and a maximum diameter W. A thermoplastic synthetic resin molded product, wherein the ratio W / H to the height H is 1.4 or less. 4. The thermoplastic synthetic resin molded article according to claim 3, wherein said deep container has a rectangular container shape. 5. The thermoplastic synthetic resin has an MFR of 20 or more and 20 or more.
5. The thermoplastic synthetic resin molded article according to claim 2, wherein the olefin resin is 0 or less.