JP2000167922A - Method and apparatus for manufacturing tubular body of resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a curved tubular body of resin having a high strength and modulus of elasticity. SOLUTION: In the method and apparatus for manufacturing a tubular body of resin 1 wherein a hollow workpiece 1 comprising a crystalline thermoplastic resin is pulled from between a die 2 and a former 3 by a clamp 5 so as to be stretched and is passed through a water tank 8 to cool it, the interior of the tank 8 is divided into two rooms, i.e., left and right rooms or upper and lower rooms, by a partition, wherein the temperature of the water in one of the rooms is made higher than that of the other one of the rooms. And the tubular body which has been cooled by bring passed through the tank 8 is heated, whereby the body is bent utilizing the residual stresses thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for manufacturing a curved resin tubular body. More specifically, the present invention relates to a method and an apparatus for manufacturing a resin tubular body by stretching a hollow tubular body (workpiece) of a stretchable crystalline thermoplastic resin.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 4-55379 and Japanese Unexamined Patent Publication No. 10-225984 disclose a method and an apparatus for manufacturing a resin tubular body, in which a hollow processed product made of a crystalline thermoplastic resin which can be stretched is used as a die. Although not enough to cause tensile failure of the hollow workpiece, the hollow workpiece supplied from the inlet side and sent to the outlet side of the die through the cone-shaped former disposed inside the hollow workpiece. A method and apparatus for manufacturing a resin tubular body including a step of applying sufficient tensile stress to stretch-deform in a solid phase, stretch-deform the hollow workpiece, and recovering the hollow workpiece from an exit side of a die. . The conical formers used here are arranged such that the maximum cross-sectional area is greater than the initial cross-sectional area of the hollow part of the hollow workpiece and the cross-section increases in the downstream direction.

The tip of a hollow workpiece (cylindrical body) pulled out of a die is chucked by a tension member (not shown). When the tension member moves to the right in the drawing, the hollow workpiece is circumferentially moved. The stretching process is performed in the (diameter expanding direction) and the tensile direction (longitudinal direction or axial direction), and a resin tubular body is manufactured. The resin tubular body drawn out of the die is drawn through the water in the water tank and cooled.

According to this method, it is possible to manufacture a resin tubular body which is biaxially stretched in the axial direction and the circumferential direction and has improved physical properties such as tensile modulus.

[0005]

The resin tubular bodies manufactured by the above-mentioned conventional method for manufacturing a resin tubular body are all straight tubular.

It is conceivable to manufacture a curved tube by injection molding, but since the tube is not stretched, its strength and elastic modulus are low.

An object of the present invention is to make it possible to efficiently manufacture a curved pipe made of synthetic resin having high strength and a high elastic modulus by the method and the apparatus for stretching a hollow workpiece.

[0008]

According to the method for producing a resin tubular body of the present invention, a hollow work made of a stretchable crystalline thermoplastic resin is supplied from the inlet side of a die, and the hollow work is subjected to tensile fracture. Although not enough to cause, by applying a sufficient tensile stress to stretch deformation in the solid phase, while pulling out the resin tubular body obtained by stretching the hollow workpiece from the exit side of the die, In the method of manufacturing a resin tubular body for cooling the resin tubular body drawn out from the outlet side of the die, in performing the cooling, the cooling rate is made different between one half side and the other half side with the axis of the resin tubular body interposed therebetween. After the cooling, a heat treatment is performed to bend the resin tubular body.

Further, the apparatus for producing a resin tubular body of the present invention comprises:
A die in which a hollow workpiece made of an extensible crystalline thermoplastic resin is sent from the inlet side to the outlet side, and the hollow workpiece is insufficient to cause a tensile fracture, but is stretched and deformed in a solid phase. Comprises means for applying a sufficient tensile stress, a cooling device for cooling the resin tubular body drawn out of the die, and a heating device for heating and curving the resin tubular body cooled by the cooling device. The cooling device is characterized in that the cooling rate can be made different between one half and the other half with respect to the axis of the resin tubular body.

According to the present invention, the resin tubular body coming out of the die is connected to one half and the other half (for example, the left half and the right half).
By cooling so that the cooling rates are different from each other, first, a straight tubular resin tubular body is obtained. This resin tubular body has different residual stresses on one half side and the other half side. Then, when the resin tubular body after cooling is heated, the resin tubular body is bent by the residual stress. The degree of this curvature can be set to a desired degree (curvature) by appropriately selecting the difference in cooling rate between the first half and the other half and the heating temperature after cooling.

The curved tube manufactured in this manner has an extremely high strength and modulus of elasticity since it has been stretched. Therefore, a curved pipe having a large effective inner diameter is provided even when the pipe has a small thickness and the same outer diameter.

In the present invention, a "hollow workpiece" to be a workpiece to be stretched is a hollow molded article having a constant cross section, and is a single piece having both open ends or only one end formed simultaneously. An open continuum may be mentioned. The cross-sectional shape of the hollow workpiece is desirably a shape having an axis of symmetry, for example, a circle, an ellipse, a square, a rectangle, or a hexagon, and a circle or an ellipse is particularly preferable.

The crystalline thermoplastic resin constituting the hollow workpiece is a resin having a crystal structure. Preferred examples of such a resin include an unsubstituted or halogen-substituted vinyl polymer, an unsubstituted or hydroxy-substituted polyester, and a polyamide. , Polyetherketone, aliphatic polyketone, polyoxymethylene and the like.

These thermoplastic resins may be blended with fibrous fillers such as glass and carbon, plate-like fillers such as talc and mica, or granular fillers such as calcium carbonate, barium sulfate and carbon.

The hollow workpiece can be formed by melting and then cooling the thermoplastic resin. In fact injection molding,
It is most practical to use extrusion molding, but it may be manufactured by cutting.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a stretching apparatus suitable for use in the method for producing a resin tubular body of the present invention.
FIG. 2 is a sectional view taken along the line II-II in FIG.

The hollow workpiece (cylindrical body) 1 is heated in an oven 4 and drawn out of the apparatus through a space between an inner periphery of a forming hole (lip) of a die 2 and an outer periphery of a conical former 3. It is a tubular body 7. The downstream end of the tubular body 7 is gripped by a clamp 5, and the clamp 5 is moved rightward in the figure at a constant speed by a tension device (not shown). The former 3 is supported by a shaft 6.

At the outlet of the die 2, a cooling water tank 8 for cooling the tubular body 7 is provided. The cooling water tank 8 is provided with a pair of holes 8 through which the tubular body 7 passes.
A and 8B are provided, a seal member 9 is provided on the peripheral edge of the holes 8A and 8B, and a cooling water is circulated from a cooling water introduction port and a discharge port (not shown). 8 to be water-cooled.

The cooling water tank 8 is preferably provided at a position where a part of the hollow workpiece 1 on the former 3 can be cooled.

In the cooling water tank 8, partitions 1 extending in the longitudinal direction of the tubular body 7 above and below the passage area of the tubular body 7, respectively.
0 and 11 are provided, and the water temperature on the left side and the water temperature on the right side of the partitions 10 and 11 are different. In addition, it is preferable that this water temperature difference is 10-80 degreeC, especially 50-70 degreeC. In addition, the water temperature of the higher temperature is 50-90.
It is preferable that it is 70 degreeC especially 70-90 degreeC.

In order to start stretching using this molding apparatus, it is necessary to cover the hollow workpiece 1 on the former 3. In this case, for example, this operation can be facilitated by cutting the inner surface of the end of the hollow workpiece. Alternatively, this work is facilitated by heating the hollow workpiece to soften it below the melting point. After placing the hollow workpiece 1 on the former 3, this end is projected through the lip of the die 2,
This is fixed to the clamp 5, and preparation for stretching is completed.

As the clamp 5, a hollow workpiece gripping mechanism such as a mechanical type, a hydraulic type, and a pneumatic type can be used.
The clamp 5 is moved by a tension device such as a motor winch via a wire, a chain, a rack and pinion, or the like. Stretching can also be performed by continuously applying a tensile force to the hollow workpiece using a pulling machine such as an endless orbiting pipe or the like that goes around endlessly. As will be described later, when the tubular body 7 that has passed through the water tank 8 is subjected to heat treatment as it is to continuously manufacture a curved tube, the endless track type tensioning device is disposed in the water tank 8 or in the vicinity of the water tank 8. Is preferred.

In order to extend the hollow workpiece in both the tensile direction (longitudinal or axial direction) and the circumferential direction (diameter increasing direction), the maximum cross-sectional area is larger than the initial cross-sectional area of the hollow portion of the hollow workpiece. Using a former and arranging the former such that the cross section increases in the downstream direction, a stress capable of giving a strain larger than the yield strain amount at the processing temperature of the crystalline thermoplastic resin constituting the hollow workpiece, that is, A stress greater than the yield stress is applied to the hollow workpiece. However, the upper limit of the applied tensile tension must be smaller than the breaking tension of the hollow workpiece.

The stretching ratio is 5 times or more, for example, 5 to 20 times.
Double is preferred.

The tubular body 7 thus produced by drawing is introduced into a heating chamber (not shown) such as an oven, and is heated to a predetermined temperature for a predetermined time (for example, an outer diameter φ60 mm made of high-density polyethylene resin; (In the case of a tubular body of about 2 mm, about 10 to 60 minutes at about 80 to 120 ° C.)
By holding, the tubular body 7 is bent by the residual stress. Since the residual stress is greater when the water temperature in the water tank 8 is lower, the tubular body 7 is curved by the heat treatment after cooling such that the side passing through the lower water temperature side is concave.

This heat treatment may be performed continuously by introducing the tubular body 7 drawn out of the water tank 8 into an oven or the like as it is, or cutting the straight tubular body 7 into a predetermined length and then heating the tubular body 7. It may be a batch type for processing.

In the above embodiment, partitions 10 and 11 are provided in the vertical direction in the water tank 8 and the water temperature is made different between the left and right in the water tank 8. However, the partitions are provided in the horizontal direction or the diagonal direction. The water temperature may be different between the upper and lower parts of the water tank 8. In this case, it is preferable that the upper side in the water tank be high-temperature water and the lower side be low-temperature water.

In the above embodiment, the tubular body is cooled by the water tank. However, the tubular body may be cooled by contact with a cooling roller.

[0030]

The present invention will be described below in more detail with reference to specific examples.

Example 1 Ethylene copolymer having crystallinity (Novatech HD HF410, commercially available from Nippon Polychem; density: 0.9)
55 g / cm ³ , MFR: 0.06 g / 10 min, melting point:
(135 ° C) is melt-extruded into a cylindrical shape using an extruder, and the outer diameter is 60 mm and the inner diameter is 30 m using a vacuum type outer diameter sizing device.
Thus, a cylindrical hollow workpiece 1 having a length of 1.7 m and a length of 1.7 m was manufactured (the initial cross-sectional area of the hollow portion: 707 mm ² ). One end of the hollow workpiece was machined so as to continuously reduce its inner diameter to 50 mm over a length of 150 mm and further to an inner diameter of 30 mm at a half apex angle of about 15 °.

A jig having a cone having a half apex angle of 15 ° and a maximum outer diameter of 70 mm is inserted into the inside of the processed end, and about 5 cm from the end is heated to 120 ° C. A nose (tapered portion) having an inner diameter of 65 mm and a length of about 100 mm was formed by applying a force to the other end face that had not been processed and propelled.

After removing the conical jig from the nose, a half apex angle 15 having an electric heating mechanism capable of maintaining the temperature at 120 ° C.
°, maximum outer diameter 62 mm (maximum cross-sectional area: 3019 m
m ² ) is inserted into an oven 4 provided with a die 2 (inner diameter 65 mm) having no taper at the downstream end, and the nose is gripped by a mechanical clamp 5. 5 was connected to the winch.

In this state, after leaving for about 3 hours until a thermal equilibrium of 120 ° C. is reached, the film is stretched at a stretching speed of 10 mm / min until the unprocessed portion of the hollow workpiece 1 reaches the downstream end of the former 3 and stopped. I let it. Further, in this state, the former 3 was pushed into the upstream side by about 2 mm, stretched again by about 10 mm, and stopped. Downstream end 3a of former 3
This former pressing operation was repeated until the position of the die was 5 mm from the end of the die 2 (die-former gap: 2.8 mm). Thereafter, the stretching was resumed at a stretching speed of 10 mm / min while monitoring the tensile tension of the winch, and the stretching was stopped by about 800 mm. The nose is removed from the clamp, and the tubular body 7 is 600 mm long and 400 mm wide.
The cooling water tank 8 having a depth of about 400 mm was passed through the holes 8A and 8B provided with the sealing member 9. This water tank 8 has partitions 10 and 11
The water temperature on the left is 70 ° C,
Cooling water was circulated so that the water temperature on the right side became 10 ° C. Again, while monitoring the winch tension, the stretching speed 1
Stretching was resumed at 0 mm / min, and after confirming that the tension was stabilized, the stretching speed was increased to 100 mm / min to perform stretching.
It was observed that the tension gradually decreased after the increase and then stabilized, and necking appeared with the change, and the hollow workpiece gradually changed from opaque to translucent. Under this condition, all of the hollow workpiece 1 is stretched to have an outer diameter of 63.5 mm and an inner diameter of 57.5 m.
m, a translucent stretched ethylene copolymer tube (tubular body 7) having a thickness of 3.0 mm was obtained.

This was allowed to cool to room temperature, cut into a length of 100 cm, and then placed in an air convection oven at 100 ° C.
Heated for 30 minutes. As a result, a curved tube having a radius of curvature of 110 cm was obtained.

[0036]

As described above, according to the method and apparatus of the present invention, a curved resin tubular body having high strength and elastic modulus can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a method and an apparatus according to an embodiment.

FIG. 2 is a sectional view taken along the line II-II in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hollow workpiece 2 Die 3 Former 4 Oven 5 Clamp 6 Shaft 7 Tubular body 8 Cooling water tank 9 Sealing member 10, 11 Partition

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Urash Ibrahim 1542-5 Koshigoe, Kamakura-shi, Kanagawa F-term (reference) 4F209 AA04 AG12 NA01 NB01 NG03 NG12 NH10 NH30 NK10 4F210 AA04 AG12 QA06 QC03 QD15 QG04 QG17 QQ01

Claims (2)

[Claims] 1. A hollow workpiece made of an extensible crystalline thermoplastic resin is supplied from the inlet side of a die, and is insufficient to cause tensile fracture in the hollow workpiece, but is stretched and deformed in a solid phase. By applying a sufficient tensile stress to the resin, the resin tubular body obtained by stretching and deforming the hollow workpiece is drawn out from the exit side of the die, and the resin that cools the resin tubular body drawn out from the exit side of the die is cooled. In the method of manufacturing a tubular body, in performing the cooling, the cooling rate is made different between one half side and the other half side with the axis of the resin tubular body interposed therebetween, and after this cooling, a heat treatment is performed to bend the resin tubular body. A method for producing a curved resin tubular body, characterized in that: 2. A die in which a hollow workpiece made of an extensible crystalline thermoplastic resin is sent from an inlet side to an outlet side, and a die which is insufficient to cause a tensile fracture in the hollow workpiece, Means for applying a sufficient tensile stress to cause the resin tube to stretch and deform; a cooling device for cooling the resin tubular body drawn from the die; and a heating device for heating and bending the resin tubular body cooled by the cooling device. The cooling device is a device for manufacturing a resin tubular body, wherein the cooling rate can be made different between one half side and the other half side with respect to the axis of the resin tubular body.