JPH09123212A - Two-layer hollow molding and its molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the operation to recycle surplus resin and at the same time, obtain a hollow molding with the superior smoothness of an inner face by extruding a non-reinforced resin in the center of its layer, into an auxiliary cavity, leaving the rest of the non-reinforced resin forming an inner layer as it is on the inner peripheral face of a reinforced resin forming an outer layer. SOLUTION: A receiving shaft 7 is slightly moved backward to such an extent that a floating core 2 can be accepted into an auxiliary cavity 6, and a communication aperture 5 is opened. At the same time, a pressure fluid is injected under pressure into a pressure port. Consequently, the floating core 2 heads for the auxiliary cavity 6, extruding the slow-cooling molten resin (almost non-reinforced resin) in the center of the non-reinforced resin into the auxiliary cavity 6 through the communication aperture 5. During this process, a reinforced resin which begins to be solidified by cooling on the outer peripheral side of a main cavity is left behind with the remaining non-reinforced resin of some thickness on the inner face side. In the wake of the floating core 2 passing by, a hollow part 11 with an almost equal diameter to the diameter of the floating core 2 is formed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hollow molded article such as a pipe and a method for molding the same. More specifically, it relates to a hollow molded article using a reinforced resin having improved mechanical properties by adding one or both of a filler reinforced material and a fiber reinforced material, and a molding method thereof.

[0002]

2. Description of the Related Art Conventionally, as a method of integrally molding a pipe with a synthetic resin, a floating core having a diameter corresponding to the inner diameter of the pipe and a pressure port for pressurizing a pressurized fluid are provided at one end of a main cavity. Using a mold that is provided with a sub-cavity at the other end of the main cavity through a communication port, fill the main cavity with molten resin, and then pressurize the pressurized fluid from the pressure port. It is known that the floating core is moved to the communication port side to form a hollow portion in the resin in the cavity, and the excess resin is pushed out from the communication port to the sub-cavity to integrally mold the hollow pipe. (JP-A-4-208425)
(Gazette: Some member names are described according to the present invention to facilitate understanding).

The above-mentioned conventional method has a major feature in that the hollow portion is formed by mainly using injection molding and pressurizing the pressurized fluid together with moving the floating core. It has the advantage that a good and highly dimensional pipe can be obtained. In addition, the molding with the reinforced resin is easy, and there is an advantage that not only a straight pipe but also a bent pipe can be manufactured as long as the bending is within a range in which the floating core can be moved.

[0004]

However, when the hollow molded article is molded by using the reinforced resin as the resin by the conventional method, there are the following problems.

(1) When a hollow molded article is molded with a reinforced resin by a conventional method, the main cavity is filled with the reinforced resin and the floating core is moved by the pressurization of a pressurized fluid to move the reinforced resin in the center of the main cavity. Will be pushed out to the sub cavity from the communication port. The reinforced resin extruded into the sub-cavity is taken out of the mold together with the hollow molded product after cooling and is usually crushed for reuse, but since the solidified reinforced resin has high strength, it is broken into large pieces. Not only can it be crushed without a device,
There is a problem that the blade of the crushing device is easily worn and is difficult to reuse. Further, in the case of a reinforced resin containing reinforced fibers, the reinforced fibers are shredded at the time of crushing, and the mechanical properties of the reinforced resin deteriorate, which also hinders reuse.

(2) The inner surface of the hollow molded product, which is formed as the surface of the reinforced resin in direct contact with the moving floating core, rubs against the floating core because the reinforced resin contains filler reinforcing material and reinforcing fibers. Therefore, there is a problem that the smoothness of the surface is significantly impaired. For example, when a hollow molded product is used as a pipe, defects such as an increase in fluid flow resistance, which is an important characteristic of the pipe, occur and the application range is significantly narrowed.

The present invention has been made in view of the above problems, and is for molding a hollow molded article which forms a hollow portion by pushing out excess resin in the main cavity by the movement of the floating core due to the pressurization of a pressurized fluid. In the method, it is an object of the present invention to facilitate the recycling of the surplus resin extruded from the main cavity when molding using a reinforced resin, and to provide a hollow molded article having excellent smoothness on the inner surface.

[0008]

To this end, according to the first aspect of the present invention, a main cavity having a pressurizing port having a floating core at one end and a sub-cavity communicating at the other end through a communication port that can be opened and closed. After injecting the molten resin into the cavity, pressurize the pressurized fluid from the pressure port to move the floating core to the communication port side and push the resin from the communication port to the sub-cavity. The outer periphery is filled with reinforced resin, and the central part of the main cavity is filled with non-reinforced resin. By moving the floating core, while leaving the non-reinforced resin forming the inner layer on the inner peripheral surface of the reinforced resin forming the outer layer, the central part The method for forming a two-layer hollow molded article is characterized by extruding the non-reinforced resin located in the sub-cavity into the sub-cavity.

According to the second aspect of the present invention, the outer layer is made of a reinforced resin and the inner layer is made of a non-reinforced resin, and the ratio T _{1 of the} thickness T _{1 of the} inner layer and the thickness T ₀ of the outer layer is T _1. / T ₀ is _{1/100 ≦ T 1 / T} 0 ≦ 5, and in which center line average roughness R _a of the inner surface is a two-layer hollow molded article, characterized in that it is 5μm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, a molding apparatus used in the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a main cavity, and the main cavity 1 has a shape along the outer shape of a main molded product 12 (see FIG. 8). The main molded product 12 in this example is a curved pipe.

A floating core 2 having a diameter corresponding to the inner diameter of the main molded product 12 (see FIG. 8) is provided at one end of the main cavity 1, and the floating core 2 is connected to the other end of the main cavity 1. A pressurizing port 3 is provided for pressurizing a pressurizing fluid to be pressed and moved to the side.

The floating core 2 is pressed by the pressurizing fluid that is press-fitted from the pressurizing port 3, so that the pressurizing port 3 can be pressed.
Is provided in the main cavity 1 with the back as
For example, in addition to metal such as copper, stainless steel, iron, and aluminum, resin may be used as long as it does not melt and deform significantly during molding. In particular, when the floating core 2 made of resin is light, the pressure of the pressurized fluid can be easily pushed and moved without increasing the pressure so much. Since the resin contacting with is less likely to be rapidly cooled, there is an advantage that the molding state of the inner surface of the main molded product 12 (see FIG. 8) on the pressure port 3 side is improved. The shape of the floating core 2 may be, for example, a conical shape, a bullet shape, a hemispherical shape or the like as long as the maximum diameter corresponds to the inner diameter of the main molded product 12, in addition to the spherical shape shown.

The pressurizing port 3 is connected to a pressurizing fluid system (not shown) for pressurizing and discharging the pressurizing fluid. The pressurizing port 3 is for causing the pressurizing fluid supplied from the pressurizing fluid system to act on the back surface side of the floating core 2 and to push and move the floating core 2 to the other end side of the main cavity 1. The pressurization fluid is press-fitted from the pressurization port 3 after the main cavity is filled with resin, so that the floating core 2 is not lifted up when the molten resin is injected and the floating core 2 is pressed into the pressurization port 3. Floating core 2 so that the main cavity 1 can be filled with molten resin while being pressed against
A gate 4 is provided at a position slightly away from the gate.

A communication port 5 is provided on the other end side of the main cavity 1, and a sub-cavity 6 is connected to the main cavity 1 through the communication port 5. The communication port 5 has a size that allows the floating core 2 to pass therethrough, but has a slightly constricted shape. The sub-cavity 6 has a structure in which the main cavity 1 is filled with resin, a pressurized fluid is press-fitted from the pressure port 3 and the floating core 2 is moved when the floating core 2 is moved. Has a volume that can be accommodated with a margin.

A receiving shaft 7 is inserted through almost the center of the sub-cavity 6 toward the communication port 5 so as to be movable back and forth. The receiving shaft 7 closes the communication port 5 by pressing the peripheral edge of the tip end against the peripheral wall of the communication port 5 when moving forward, and opens the communication port 5 when moving backward. In addition, the tip of the receiving shaft 6 can mount the floating core 2 that moves to the sub-cavity 6 when the pressurized fluid is press-fitted.

In this example, the communication port 5 is opened and closed by advancing and retracting the receiving shaft 7, but the opening and closing of the communication port 5 may be performed not by the receiving shaft 7 but by another opening and closing means. .

To inject the molten resin into the main cavity 1 of the mold, an injection device used for so-called two-color molding or two-layer molding is used. For example, as shown in FIGS. 2 and 3, there is used an injection device including two injection cylinders 8a and 8b and capable of injecting two kinds of resins without mixing them. Reinforcing resin containing at least one of filler reinforcement and fiber reinforcement is injected from one injection cylinder 8a, and non-reinforced resin containing neither filler reinforcement nor fiber reinforcement is injected from the other injection cylinder 8b. It is a thing. In the injection device shown in FIG. 2, two injection cylinders 8a and 8b are connected to an injection nozzle 10 via a switching valve 9, and the injection cylinders 8a and 8b are connected to each other.
It is possible to eject while switching b. Further, in the injection device shown in FIG. 3, the injection cylinder 8 is attached to the center of the resin extruded from the injection cylinder 8a.
The resin of b is extruded, and the resin having a double structure can be injected from the injection nozzle 10.

Next, the molding method of the present invention using the molding apparatus as described above will be described.

First, as shown in FIG. 4, the receiving shaft 7 is advanced to inject the reinforced resin and the non-reinforced resin into the main cavity 1 with the communication port 5 closed. This injection is performed so that the outer peripheral portion of the main cavity 1 is filled with the reinforced resin and the central portion of the main cavity 1 is filled with the non-reinforced resin. Specifically, when the injection device of FIG. 2 is used, the reinforced resin is first injected from the injection cylinder 8a, and then the switching valve 9 is switched to inject the non-reinforced resin from the injection cylinder 8b. When the injection device of FIG. 3 is used, the injection of the reinforced resin from the injection cylinder 8a and the injection of the non-reinforced resin from the injection cylinder 8b are performed almost at the same time (the injection of the reinforced resin is slightly advanced).

The reinforced resin in the present invention means a resin having improved mechanical properties by adding one or both of a filler reinforced material and a fiber reinforced material. Examples of the base resin of the reinforcing resin include polystyrene resin, polyolefin resin, polyamide resin, acrylic resin, PO
General thermoplastic resins such as M, PPS, modified PPE, and polycarbonate can be widely used. As the filler reinforcing material, for example, talc, wollastonite, calcium carbonate or the like can be used, and as the fiber reinforcing material, for example, glass fiber, carbon fiber, metal fiber or the like can be used. The content of these filler reinforcing material and / or fiber reinforcing material in the reinforcing resin is selected according to the physical properties required for the application, but is generally 5% by weight or more. Further, the reinforced resin in the present invention contains at least one of the filler reinforced material and the fiber reinforced material as described above, but in the case of the reinforced resin containing the fiber reinforced material, the above-mentioned problems are remarkable, The benefits of applying the invention are also great.

The non-reinforcing resin in the present invention means a resin to which the improvement of mechanical properties by the filler reinforcing material or the fiber reinforcing material as described above is not imparted. Basically, it is a resin that does not contain filler reinforcement and fiber reinforcement,
The filler-reinforced material and / or the fiber-reinforced material may be contained in a range that does not impair the smoothness of the inner surface (which is also a range in which substantially no improvement in mechanical properties is obtained), which will be described later. Specifically, one or both of the filler-reinforced material and the fiber-reinforced material may be contained within the range of 3% by weight or less. As the non-reinforced resin, the same thermoplastic resin as the base resin of the above-mentioned reinforced resin can be used. This non-reinforced resin and the base resin of the above-mentioned reinforced resin may be of the same kind or of different kinds, but in order to firmly fuse the outer layer 15 and the inner layer 16 (see FIG. 9) of the obtained molded product and to integrate them. The same type of resin is preferable.

If desired, various additives and colorants may be added to the reinforced resin and the non-reinforced resin.

Then, as shown in FIG. 5, the receiving shaft 7 is slightly retracted to the extent that the floating core 2 is received in the sub-cavity 6, the communication port 5 is opened, and the pressurized fluid is supplied from the pressurizing port 3. Press fit. As a result, the floating core 2 leaves the reinforced resin on the outer peripheral side of the main cavity where the cooling and solidification has started, and leaves the unreinforced resin with a certain thickness on the inner surface side of the reinforced resin, while cooling the molten resin in the central portion where cooling is delayed. (Mostly unreinforced resin) is pushed into the sub-cavity 6 through the communication port 5 and advances toward the sub-cavity 6. After the floating core 2 has passed, a hollow portion 11 having a diameter substantially equal to the diameter of the floating core 2 is formed. Therefore, the diameter of the hollow portion 11 formed can be adjusted by selecting the diameter of the floating core 2. Then, the resin in the portion where the hollow portion 11 is formed is pressed against the peripheral wall surface of the main cavity 1 by the pressure of the pressurized fluid that is press-fitted, and the shape thereof is maintained.

As the above-mentioned pressurized fluid, a gas or liquid that does not react with or be compatible with the resin used at the temperature and pressure of injection molding is used. Specifically, nitrogen gas, carbon dioxide gas, air, glycerin, liquid paraffin, etc. can be used, but an inert gas such as nitrogen gas is preferable. In the case of using a gas such as nitrogen gas, the pressurization of the pressurized fluid is performed by introducing the pressurized gas, which has been stored in the accumulator (not shown) by a compressor, to the pressurization port 3 through a pipe. Alternatively, it can be carried out by directly sending a pressurized gas to the pressurizing port 3 with a compressor to successively raise the pressure. In the former case, the pressure of the pressurized gas supplied to the pressure port 3 varies depending on the type of resin used and the like, but is usually 50 to 50.
It is about 300 kg / cm ² G.

When the pressurization of the pressurized fluid is further advanced, the floating core 2 is moved to the sub-cavity 6 as shown in FIG.
It enters and is placed on the receiving shaft 7. Further, the sub cavity 6 is filled with the resin extruded from the communication port 5 and the pressurized fluid that has pushed the floating core 2 and entered the sub cavity 6. Almost all of the reinforced resin on the outer peripheral side of the main cavity 1 remains in the main cavity, but all the non-reinforced resin in the center of the main cavity 1 is extruded into the sub-cavity 6 except remaining on the inner surface side of the reinforced resin. Will be done. As a result, most of the resin in the sub-cavity 6 becomes a non-reinforced resin, which facilitates its recycling.
In order to further facilitate this recycling, the volume of the sub-cavity 6 is made small, and a waste cavity having a small cross-sectional area (not shown) is connected to the sub-cavity 6 so that the extruded resin is easily crushed into a thin or thin shape. It is preferably taken out as a sub-molded product 13 (see FIG. 8).

Although the resin may be cooled in the state shown in FIG. 6, when the receiving shaft 7 is retracted as shown in FIG. 7, the hollow portion 11 in the sub-cavity 6 is expanded in accordance with this retraction. However, the wall thickness of the sub-molded product 13 (see FIG. 8) can be reduced to facilitate crushing during recycling. In any case, the resin is cooled while the pressure in the mold is maintained, the pressurized fluid in the hollow portion 11 is discharged, and then the receiving shaft 7 is retracted from the sub-cavity 6 to take out the molded product. The discharge of the pressurized fluid can be performed by opening the pressure port 3 to the atmosphere when gas is used as the pressurized fluid, but the pressurized fluid is recovered in a recovery tank (not shown) for recycling. It is preferable.

The molded product taken out is as shown in FIG. 8, and the main molded product 12 molded in the main cavity 1 is used.
And a sub-molded product 13 molded in the sub-cavity 6. Since the thin constricted portion 14 formed by the constricted communication port 5 is interposed between the main molded product 12 and the sub molded product 13, the main molded product 12 is connected to the sub molded product 13 through the constricted portion 14. It is possible to easily separate the hollow molded article from the above, whereby the hollow molded article of the present invention (a curved pipe in this example) can be obtained. As described above, since the floating core 2 is placed on the receiving shaft 7 in the sub-cavity 6 and remains in the sub-molded product 13,
The resulting hollow molded product has both ends open from the beginning.

The hollow molded article (main molded article 12) of the present invention is
As shown in FIG. 9, the outer layer 15 formed of a reinforced resin
And a two-layer structure including the inner layer 16 formed of non-reinforced resin. The outer layer 15 formed of the reinforced resin brings high mechanical strength to the hollow molded article. Moreover, the inner layer 16 formed of the non-reinforced resin provides a smooth inner surface.

In a hollow molded article having a predetermined outer diameter and inner diameter,
The thickness T _{0 of the} outer layer 15 formed of the reinforced resin and the thickness T _{1 of the} inner layer 16 formed of the non-reinforced resin are the injection capacity of each resin, the timing of starting the injection of the reinforced resin and the subsequent non-reinforced resin. (Injection delay time: time from injection of reinforced resin to start of injection of non-reinforced resin). The injection delay time is the required T
Selected by ₁ , T ₀ , T ₁ / T ₀ ,
Also, depending on the type of resin used, it is usually 0 to
30 seconds.

In the hollow molded article of the present invention, 1/10
It is necessary that 0 ≦ T ₁ / T ₀ ≦ 5. If this ratio is less than 1/100, the smoothness of the inner surface becomes poor,
When the hollow molded article of the present invention is used as pipes, the flow resistance of the fluid becomes too large. If this ratio exceeds 5, the strength required for the hollow molded article cannot be obtained. 1/2 to obtain higher internal smoothness and strength
It is preferable that 0 ≦ T ₁ / T ₀ ≦ 2. In particular, when used as pipes for which fluid flows for a long period of time and internal pressure is applied, it is desirable to satisfy the condition of 1/20 ≦ T ₁ / T ₀ ≦ 2.

In the hollow molded product of the present invention, it is necessary that the center line roughness _Ra (JIS B0601) of the inner surface is 5 μm or less. When the center line roughness _Ra is 5 μm or more, not only the flow resistance to the fluid when the hollow molded product is used as a pipe becomes too large, but also
Cracks are likely to occur from the uneven parts, making it difficult to withstand long-term use. This centerline average roughness _Ra is extracted from the extraction curve by extracting the portion of the evaluation length L in the direction of the centerline, extracting the centerline of the extracted portion as the X axis, and extracting the direction of longitudinal magnification as the Z axis. When a curve is represented by Z = f (x), it means the display in μm unit obtained by the following formula.

[0033]

(Equation 1)

In the above description, the case of forming a curved pipe is taken as an example, but the present invention is not limited to this, and a straight pipe or other hollow material may be used.

[0035]

【Example】

Example 1 Using a mold as shown in Fig. 1, an injector having two U-shaped pipes having an outer diameter of 3 cm, an inner diameter of 2.4 cm, a wall thickness of 3 mm, and a total length of 35 cm (manufactured by Battenfeld). "BMT4000"). A steel ball having a diameter of 2.4 cm was used as the floating core, and a gas generator for gas hollow injection molding (“air mold” manufactured by Asahi Engineer Link Co., Ltd.) was used to supply the pressurized fluid. Nitrogen gas was used as the pressurized fluid.

As the reinforcing resin for forming the outer layer,
Polyamide 66 (“Leona 1300G” manufactured by Asahi Chemical Industry Co., Ltd.) containing 33% by weight of glass fiber, and polyamide 66 (“Leona 1300S” manufactured by Asahi Chemical Industry Co., Ltd.) was used as the non-reinforced resin forming the inner layer.

First, the above-mentioned non-reinforced resin is heated to a resin temperature of 290.
° C., injection pressure 90 kg / cm ² emitted by G, then the reinforced resin resin temperature 290 ° C. After 0.1 seconds, injection pressure 60 kg / cm ² emitted by G, a pressure 100 kg / cm after completion of injection 1 second Nitrogen gas ( ² ) was pressed in to move the floating core in the mold, and after cooling for 30 seconds, the molded product was taken out.

The resulting molded article, Hobosoto径3 cm ,, inner diameter 2.4 cm, thickness 3 mm, a pipe of U-shaped overall length 35 cm, the center line average roughness R _a of the inner surface "SURFCOM 57
5A-3D470 "was measured by (Tokyo Seimitsu Corp.), is a R _a = 1.5μm, it was excellent in smoothness.

Ratio T _{1 of} thickness T _{1 of the} inner layer and thickness T ₀ of the outer layer
As for / T ₀ , as a result of measuring the thickness of each of the obtained pipes at 10 points, the average is T ₁ / T ₀ = 1/2, the minimum is T ₁ / T ₀ = 1/4, and the maximum is T 1. ₁ / T ₀ = 1.

The resulting pipe was filled with hot water at 80 ° C. at 3 kg /
As a result of carrying out a 1000-hour durability test by applying an internal pressure of cm ² , it showed sufficient performance as an industrial pipe without causing problems such as an increase in flow resistance and occurrence of cracks. In addition, almost 85% of the resin extruded into the sub-cavity
Wt% is non-reinforced resin without glass fiber,
It could be easily crushed with a small crusher and reused.

[0041]

Industrial Applicability The present invention is as described above, and it is possible to easily reuse the surplus resin and reduce the cost of the product by suppressing the wasteful consumption of the resin. Further, the obtained hollow molded product is not only excellent in mechanical strength, but also has a smooth inner surface and is suitable as a pipe having a small flow resistance to a fluid.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a mold used in the present invention.

FIG. 2 is a diagram showing an example of an injection machine used in the present invention.

FIG. 3 is a diagram showing another example of an injection machine used in the present invention.

FIG. 4 is an explanatory diagram of a molding procedure of the present invention, showing a state in which the main cavity is filled with a reinforced resin and a non-reinforced resin.

FIG. 5 is an explanatory diagram of a molding procedure of the present invention, showing a state immediately after the start of pressurization of a pressurized fluid.

FIG. 6 is an explanatory diagram of a molding procedure of the present invention, showing a state in which the floating core is moved in the sub-cavity by pressurization of a pressurized fluid.

FIG. 7 is an explanatory view of the molding procedure of the present invention, showing a state in which the receiving shaft is retracted and the hollow portion in the sub-cavity is enlarged.

FIG. 8 is a view showing the obtained molded product.

FIG. 9 is an enlarged cross-sectional view of a main molded product (hollow molded product).

[Explanation of reference numerals] 1 main cavity 2 floating core 3 pressurizing port 4 gate 5 communication port 6 sub-cavity 7 receiving shaft 8a, 8b injection cylinder 9 switching valve 10 injection nozzle 11 hollow part 12 main molded product 13 sub molded product 14 constriction Part 15 Outer layer 16 Inner layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B29K 105: 12 B29L 22:00

Claims (4)

[Claims] 1. A molten resin is injected into a main cavity having a pressure port having a floating core at one end and a sub-cavity communicating through an openable / closable communication port at the other end, and then the pressure port is discharged from the pressure port. In the hollow molding method that pressurizes a pressurized fluid to move the floating core to the communication port side and extrude the resin from the communication port to the sub-cavity, reinforced resin on the outer periphery of the main cavity and non-reinforced on the center of the main cavity. It is characterized by filling each resin, and by moving the floating core, while leaving the non-reinforced resin forming the inner layer on the inner peripheral surface of the reinforced resin forming the outer layer, the non-reinforced resin located in the center is pushed out to the sub-cavity. And a method for forming a two-layer hollow molded article. 2. An outer layer formed of a reinforced resin and an inner layer formed of a non-reinforced resin, wherein a ratio T ₁ / T _{0 of} a wall thickness T _{1 of the} inner layer and a wall thickness T ₀ of the outer layer is 1/100. ≤T ₁ / T ₀ ≤
5 a and, and center line average roughness R _a of the inner surface 5μm
A two-layer hollow molded product characterized by the following: 3. A two-layer hollow molded article molded by the method of claim 1. 4. The ratio T of the thickness T _{1 of the} inner layer and the thickness T ₀ of the outer layer.
₁ / T ₀ is _{1/100 ≦ T 1 / T} 0 ≦ 5, and two-layer hollow molded article according to claim 3 in which the center line average roughness R _a of the inner surface and wherein the at 5μm or less.