JPH10151648A - Polyvinyl chloride resin molded product and injection molding of polyvinyl chloride resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and economically produce a thick-walled and/or large-sized molded product from a polyvinyl chloride resin by injection molding. SOLUTION: In subjecting a molded product with a polyvinyl chloride resin vol. of 15l or more to injection molding by an injection molding machine 11 wherein a plunger 13 being an extruder is fitted in the accumulator 12 communicating with 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, the temp. of the resin molten matter 34 in the accumulator 12 is set to 180-220 deg.C and the temp. of the resin molten matter 34 injected into the mold 14 from the emitting orifice of the leading end of the accumulator 12 is set to 170-220 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article of a polyvinyl chloride resin and an injection molding method of the polyvinyl chloride resin.

[0002]

BACKGROUND OF THE INVENTION Polyvinyl chloride resins have excellent mechanical properties and are used as materials for various injection molded articles, but are liable to undergo thermal degradation and thermal decomposition during injection molding.
Therefore, in the case of a relatively small molded product, injection molding of polyvinyl chloride resin is possible, but in the case of a thick molded product in which a large amount of resin is molded at a time or a large molded product, the cylinder of the injection molding machine is used. The storage time of the polyvinyl chloride-based resin melt in the inside becomes longer, and thermal degradation and thermal decomposition of the polyvinyl chloride-based resin easily occur during storage, which makes the flowability of the polyvinyl chloride-based resin unstable. This made injection molding difficult.

[0003]

2. Description of the Related Art As means for shortening the storage time of a polyvinyl chloride resin melt in a cylinder of an injection molding machine,
There is provided an injection molding machine in which a resin melt extruded from an extruder of an injection molding machine is temporarily stored in an accumulator, and the resin melt is injected into a mold from the accumulator by a plunger. More recently, for example, FIG.
As shown in (1), there is provided an injection molding machine (1) which doubles as an extruder and a plunger. In the injection molding machine (1) shown in FIG. 4, (2) is a cylinder and a raw material inlet is provided at the root end.
(3) is provided, (4) is a screw, which is slidably mounted in the cylinder (2) in the axial direction, and a mold is provided in the discharge port (5) of the cylinder (2). (6) is connected.

[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 resin melt 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 resin 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, even in the above-mentioned injection molding machine (1), a large amount of resin can be used at once, for example, as a substitute for a concrete product, a thick molded product such as a structural material, or a large molded product. In order to perform injection, a large and expensive one having a large-diameter cylinder with a storage amount commensurate with it is required.In the case of the above-mentioned injection molding machine (1), the screw (4) is retracted to remove the resin. Since the molten material is stored at the tip of the cylinder (2), as the screw (4) moves backward, the melt processing area of the raw material becomes shorter, and the kneading and melting state of the raw material stored at the tip of the cylinder (2) is reduced. It is easy to become uneven, the fluidity of the resin, that is, the moldability is not stable, and the thicker the molded product, the easier it is for molding defects such as sink marks and voids to occur, and the resin melt after injection molding Accurate because it remains in the cylinder (2) There was a problem that it was difficult to obtain an injection amount and that the resin melt was 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 bulging portion (19) and a resin 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) The plunger (13) consists of a polyvinyl chloride-based tip that is injection-molded by an injection molding machine (11) that has a pointed shape that matches the inside shape of the accumulator (12) tip (15). A resin molded article, wherein the polyvinyl chloride resin constituting the molded article has a capacity of 15 l or more, and provides a polyvinyl chloride resin molded article. The resin temperature in the accumulator (12) of the injection molding machine (11) was set to 180 to 220 ° C. The resin temperature emitted from the tip discharge opening (16) at the time of the form 17
An object of the present invention is to provide an injection molding method of a polyvinyl chloride resin set at 0 to 220 ° C. The molded article of the polyvinyl chloride resin to which the present invention is applied is, for example, a thick molded article having a thickness of 10 mm or more, and the molded article has, for example, a container shape, a groove shape, or a panel shape.

[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 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)) The ratio is set to 2: 1 to 10: 1.

If the gap (23) is set at 0.03 to 0.5 mm, the resin 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 resin melt (34) to enter the gap (23) smoothly, and the resin melt (34) may be seized. If the gap (23) exceeds 0.5 mm, the accumulator (12)
The residual amount of the resin melt (34) in the inside increases or the gap (23)
This causes a problem that leakage of the resin melt (34) occurs.

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 resin melt (34) in the accumulator (12) is prolonged, and the resin melt (34) may become non-uniform. There is a risk of uniformity. Within the range of the set ratio, the temperature distribution and the uniformity of the molten state of the resin melt can be maintained and the fluidity can be stabilized, so that injection molding can be performed at a low injection pressure. Furthermore, in the injection molding machine (11) of the present invention, the discharge port (16) of the accumulator (12) and the gate of the mold (14) are provided.
The diameter of (26) is set to 3 to 10 times the diameter of the nozzle of an ordinary injection molding machine to reduce the flow resistance of the resin melt (34) at the nozzle, and is stored in the accumulator (12). It is desirable to inject the resin melt (34) in a short time as possible and at a low injection pressure.

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, the fixed-side template (24) and the movable-side template (25) include, for example, a heating hot water pipe (29, 30).
Are disposed, and if desired, near the peripheral surfaces of the fixed-side template (24) and the movable-side template (25), that is, the peripheral surface of the cavity (27), the peripheral surface of the high-frequency induction heating method is used. Heating device (31, 32)
May be arranged.

The polyvinyl chloride resin used in the present invention is a homopolymer of vinyl chloride, or a resin mainly composed of vinyl chloride, and a small amount of vinylidene chloride, acrylic ester, methacrylic ester, styrene, vinyl acetate, acrylonitrile. , Ethylene, propylene, copolymers with other vinyl monomers that can be copolymerized with vinyl chloride such as butadiene, or the above-mentioned homopolymer or the above-mentioned copolymer as a main component, and a little polyethylene, polypropylene, ethylene -Propylene copolymer, ethylene-vinyl acetate copolymer, 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-EPDM-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 thermoplastic elastomer, polyamide thermoplastic elastomer, polybutadiene thermoplastic elastomer, polyurethane thermoplastic Elastomer,
It is a mixture of styrene butadiene rubber, butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, isobutylene-isoprene rubber, and the like, and contains at least 40% by weight of a vinyl chloride component. The polyvinyl chloride resin can be used whether it is a new synthetic resin or a regenerated synthetic resin.

In the present invention, an inorganic filler may be added to the polyvinyl chloride resin in an amount of 50% by weight or less. Examples of the inorganic filler include glass fiber, carbon fiber, ceramic fiber, and rock. There are inorganic fibers such as wool and metal fibers, carbon black, calcium carbonate, talc, clay, kaolin, mica, alumina, aluminum hydroxide, silicic acid, silicates, various cements, fly ash, sludge incineration ash and the like. When inorganic fibers are used as the inorganic filler, for example, 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, polyvinyl chloride resins further include, for example, lead salts such as lead white, tribasic lead sulfate, dibasic lead phosphite, lead stearate, barium stearate,
Metallic soaps such as barium ricinoleate, organic tins such as dibutyltin maleate, dibutyltin mercaptide, nonmetallic stabilizers such as epoxy compounds, phenolic compounds, antioxidants such as organic phosphite compounds, Benzophenone-based, benzotriazole-based ultraviolet absorbers, anti-aging agents, phthalate-based plasticizers, pigments such as titanium white, chrome yellow, navy blue, carbon black, red iron, coloring agents, fatty acid-based waxes, metals A lubricant such as soap, an antistatic agent such as a surfactant, an impact enhancer and the like may be added. In particular, the use of suitable heat stabilizers is required.

In the above-mentioned injection molding machine (11), a polyvinyl chloride resin (33), which is a molding raw material, is charged from a resin charging port (18), and a screw (20) of a plunger (13) is rotated. The resin (33) is melted and kneaded in a cylinder (17) by heating with a heating means not to be heated, and the plunger (13) is retracted. The resin melt (34) is accumulated in an accumulator as shown in FIG. Store it in the rotator (12). In this case, the resin temperature in the accumulator (12) is 180 to 220.
Set to ° C. If the temperature is lower than 180 ° C., the resin melt viscosity is too high and it is difficult to inject the resin into the mold (14). If the temperature exceeds 220 ° C., the resin may be thermally degraded and decomposed in the accumulator (12). is there.

The resin melt (3) is placed in the accumulator (12).
When the predetermined amount of 4) is stored, the mold (14) as shown in FIG.
The fixed mold plate (24) and the movable mold plate (25) are brought into close contact with each other, and if desired, the mold (14) is heated to a predetermined temperature by a hot water pipe (29, 30). And screw (2) of plunger (13)
(0) is stopped, the plunger (13) is advanced, and the cavity is discharged from the discharge port (16) of the accumulator (12) through the gate (26) and the sprue (28) of the mold (14). The resin melt (34) is injected into (27). The injection molding at this time is usually 50 to 700 kgf / cm ^2, and the temperature of the resin melt (34) at the tip discharge port (16) is set in the range of 170 to 220 ° C. by adjusting the filling speed and the injection pressure. . If the temperature is lower than 170 ° C., the viscosity of the resin melt (34) becomes high, which hinders injection molding. If the temperature exceeds 220 ° C., the resin may be thermally degraded and thermally decomposed. In order to prevent the viscosity of the resin melt (34) from decreasing, only the vicinity of the peripheral surface of the cavity (27) of the mold (14) is heated to 100 to 20 by a heating device (31, 32).
It may be heated to a predetermined temperature in the range of 0 ° C.

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 initially opened slightly and the gas in the cavity (27) is opened. (air)
After that, the fixed side mold plate (24) and the movable side mold plate (25) are completely closed and injection compression molding is performed.

Example 1 An injection molding machine (11) having a mold clamping force of 650 tons is used, and a molding raw material resin (33) having the following composition is used. Vinyl chloride homopolymer 100 parts by weight Methyl methacrylate-butadiene-styrene copolymer 3 parts by weight Calcium carbonate 10 parts by weight Lead-based stabilizer 3 parts by weight Pigment 1.5 parts by weight The above molding material resin is placed in a plunger (13). The mixture was heated to 200 ° C. and melt-kneaded. For injection molding, use a hot water pipe (2
The mold (14) is heated to 50 ° C. by means of (9, 30), and the vicinity of the peripheral surface of the cavity (27) is heated for 5 seconds by the heating device (31, 32) immediately before injecting the resin melt (34). Heat to 180 ° C. The time (filling time) for filling the resin melt (34) from the plunger (13) into the accumulator (12) is 5 minutes, the temperature of the resin melt (34) is 190 ° C., and the accumulator (1)
The time to inject the resin melt (34) from 2) to the mold (14) is 2
The injection pressure was set at 600 kgf / cm ² , and the temperature of the resin melt (34) at the tip discharge port (16) was set at 190 ° C. By the above-mentioned injection molding, a disk-shaped molded product having an average thickness of 15 mm, a maximum thickness of 20 mm, an outer diameter of 1100 mm, and a resin capacity of 19 l was manufactured in a molding cycle of 12 minutes. No generation of sink marks and voids was found in the molded product.

Comparative Example A conventional injection molding machine shown in FIG.
Injection molding of the same molded article as in Example 1 by (1) requires an injection molding machine with a mold clamping force of 3000 tons and an injection pressure of about 1000 kgf / cm ^2. The mold cost was twice as high as that of the first embodiment in order to withstand a high injection pressure. In addition, sink marks and voids were observed in the molded product despite the application of such high injection molding pressure.

Embodiment 2 The same injection molding machine (1
1) is adjusted to a clamping force of 450 tons and used, and a molding material resin (33) having the following composition is used. Polyvinyl chloride: ABS resin = 1: 1 weight ratio Polymer alloy 100 parts by weight Fly ash 30 parts by weight Lead-based stabilizer 3 parts by weight Pigment 2 parts by weight The above molding material resin is heated to 195 ° C. in a plunger (13). And melt-kneaded. 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 this embodiment, the fixed side mold plate of the mold (14) was used at the beginning of injection molding. A gap of 5 mm was provided between the mold (24) and the movable mold plate (25), and the mold (14) was started to be closed 90 seconds after the start of injection and completely closed in 20 seconds. In this embodiment, the time for charging the resin into the accumulator (12) is 4.5 minutes, the temperature of the resin melt (34) in the accumulator (12) is 195 ° C., the injection time is 1.5 minutes, and the injection pressure is 590. kgf / cm ² , tip outlet (16)
The temperature of the resin melt (34) is 190 ° C., a U-shaped groove having a uniform average thickness of 12 mm and a resin capacity of 17 l, which is uniform and has good surface properties as in Example 1, and has no deformation. A shaped article was obtained.

[0020]

According to the present invention, a polyvinyl chloride resin which is easily denatured and thermally decomposed is used as a material to stably and economically produce a thick and / or large molded product without sink marks and voids, for example, a substitute for a concrete product. Into a product by injection molding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 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 Resin inlet 19 Tip bulging part 20 Screw 21 Tip outside part 34 Resin 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 (7)

[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 resin inlet at a root end thereof, and a screw rotatably mounted in the cylinder, the tip of the screw coming out of the cylinder tip, and the tip of the screw The tip of the plunger, which is composed of an outer portion and a swelling portion of the tip of the cylinder, is a polyvinyl chloride resin molded product injection-molded by an injection molding machine having a pointed shape adapted to the inside shape of the accumulator tip. Characterized in that the volume of the polyvinyl chloride resin constituting the molded product is 15 l or more. 2. The polyvinyl chloride resin molded article according to claim 1, wherein the average thickness of the polyvinyl chloride resin molded article is 10 mm or more. 3. The polyvinyl chloride resin molded article according to claim 1, wherein the shape of the polyvinyl chloride resin molded article is a container shape, a groove shape, or a panel shape. 4. An accumulator having a die gate connected to a tip discharge port, and a plunger slidably fitted to the accumulator. A cylinder provided with a resin inlet at a root end thereof, and a screw rotatably mounted in the cylinder, the tip of the screw coming out of the cylinder tip, and the tip of the screw In molding a polyvinyl chloride resin with an injection molding machine having a pointed shape adapted to the inside shape of the accumulator tip portion, the plunger tip portion comprising an outside portion and a tip swelling portion of the cylinder forms the accumulator. The temperature of the resin in the radiator is set to 180 to 220 ° C., and the temperature of the resin injected from the tip discharge port during the injection molding is set to 170 to 220 ° C.
Injection molding method for polyvinyl chloride resin characterized by setting to 220 ° C. 5. The injection molding method for a polyvinyl chloride resin according to claim 4, wherein the volume of the polyvinyl chloride resin constituting the molded article of the polyvinyl chloride resin molded by the injection molding method is 15 l or more. 6. The method for injection molding a polyvinyl chloride resin according to claim 4, wherein said molded article molded by said injection molding method has an average thickness of 10 mm or more. 7. The injection molding method for a polyvinyl chloride resin according to claim 4, wherein the shape of the molded article molded by the injection molding method is a container shape, a groove shape, or a panel shape.