JPH0571375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a sizing method and apparatus for manufacturing foamed pipes made of thermoplastic resins such as vinyl chloride resins.

<Prior art> Conventional pipe sizing methods include multi-plate sizing, air pressure sizing, dry vacuum sizing, and wet vacuum sizing. There is a device shown in the figure.

<Issues> Among the conventional methods, multi-plate sizing is for solid profile molding and is not suitable for foam molding, and air pressure sizing involves plugging the pipe and
Since air pressure is applied to the inside of the pipe for sizing, the contact pressure between the pipe and the sizing die is large, making it unsuitable for foamed products as they will stretch when taken out.
In addition, dry vacuum sizing is also not suitable for sizing foam products because it similarly stretches when taken off.
Only wet vacuum sizing is used in foam extrusion. In this method, the high-temperature pipe is extruded by reducing the pressure in the water tank, and is passed through the cooling water tank while maintaining the reduced pressure, and is cooled while maintaining its shape due to the expansion of the atmospheric pressure inside the pipe. It is. However, although this method is an effective means, there is a problem in that the device must be expensive.

In addition, in the apparatus shown in FIGS. 8 and 9, the foamed extrudate B extruded from the die of the extruder passes through the sizing die provided inside the cooling water tank C (No. 8). The length of the sizing die is usually 250 to 300 mm because the foamed extrudate B passes through a sizing die having a cooling water tank E and inside the cooling water tank C (Figure 9).
This is necessary, and the resistance caused by the contact between the foamed resin and the sizing die is large, causing the product to stretch when taken off. Furthermore, since it is a foamed product, even after passing through the sizing die, there is a risk that it may easily deform due to insufficient cooling, and there was also a problem in dimensional accuracy. The present invention has been made in view of the above circumstances, and is intended to provide an apparatus that is capable of sizing foamed resin pipes and is inexpensive in equipment cost.

<Means for Solving the Problems> The present invention has taken measures to solve the above problems by extruding a molten foam pipe while supporting the molten resin with an expansion cap attached to the tip of a mandrel of an extruder, and The foamed pipe is cooled by a first sizing die consisting of a cooling jacket, and a second sizing die consisting of a plurality of vacuum jackets installed at predetermined intervals in the extrusion direction in an atmosphere of sprayed water and having a large number of suction holes on the inner wall surface. The pipe is successively corrected using a sizing die, and then passed between adjustment rolls that rotate at intervals matching the outer diameter of the pipe installed in the water tank.

<Function> With the above means, the present invention eliminates the need to lengthen the sizing die, regulates cooling with a cooling jacket, straightens with a vacuum jacket, and forms a uniform water film on the surface of the cooling pipe with sprayed water, reducing frictional resistance. It can be made smaller and can be sized without being deformed by adjustment rolls.

<Example> An example of the implementation of the present invention will be described based on the drawings. Extruder A is configured to feed a thermoplastic resin compound containing a foaming agent from a so-called hopper having a shape and structure well known in this technical field, and extrude the screw. The molten foamed resin is extruded from a die into a pipe shape by the rotation of the extruder A, and an expansion cap b is attached to the tip of a pipe die mandrel a provided at the tip of the extruder A. This expansion cap b has a conical cap 2 on the core rod 1.
and a plurality of rings 3 are attached in a skewer shape, and the tip of the core rod 1 is screwed to the tip of the mandrel a, so that the molten foamed resin extruded from the mouth hole and the air blown through the mandrel a are shaped like a cone. It passes through the conical cap 2 and the plurality of rings 3 while being sent out through the ventilation hole provided in the cap 2. Therefore, it is desired that the substantially conical cap 2 and ring 3 be made of a material that has good adhesion to the molten resin and allows for smooth movement.A suitable material for this purpose is a heat-resistant material. It is preferable to use a material made by cutting and molding a good fluororesin.

Also, it is preferable that the outer diameter of the cap 2 and the ring 3 is about 10% smaller than the inner diameter of the pipe to be molded, and the overall length of the expansion cap b is also the same as the die of the extruder A and the cooling jacket B. The length is the length necessary to maintain the distance between rings 3 at a predetermined interval, and the length can be adjusted by adjusting the number of rings 3, although it varies depending on the diameter of the pipe, extrusion speed, and various other requirements. As a result, the molten resin is sufficiently foamed and drawdown of the resin is prevented. For this reason, the distance between the tip of the mandrel of extruder A and the cooling jacket B is generally 25 to 30 mm, preferably 100 to 200 mm.

The cooling jacket B is a first sizing die for regulating or forming the melt-foamed pipe to a desired outer diameter and cooling it, and is attached to the tip of the water tank D. This cooling jacket B has a form in which cooling water is passed through or stored therein, and connecting pipes 4 are connected to the supply port and the discharge port, respectively, and the cooling water is used to form a thin layer on the surface of the foamed pipe passing through the inside of this cooling jacket B. A skin layer is formed to reduce the frictional resistance between the cooling jacket and the pipe, resulting in smooth passage.
This cooling jacket B preferably has a length of about 50 to 100 mm. If it is less than 50 mm, the cooling of the pipe surface will be insufficient, and if it is more than 100 mm, the resistance when the pipe passes will increase and there is a risk that it will stretch when it is pulled out.As for the material, brass has good thermal conductivity and is resistant to corrosion. It is preferable to manufacture it with

The pipe that has passed through this cooling jacket B is inserted into a vacuum jacket C as a second sizing die in an atmosphere of spray water.

The vacuum jacket C has a large number of absorption holes (slits) 5 formed on its inner wall, and is connected to a vacuum pump (not shown) through a pipe 6 through a connection port, so that the pipe is absorbed by the large number of suction holes and straightened into a perfect circle. Make it.
It is desirable that a plurality of vacuum jackets C be installed at predetermined intervals in the direction in which the pipes travel, and that vacuum pipes be connected to each one independently, so that the suction power is gradually increased as cooling progresses. For example, the first vacuum jacket c ₁ has a weak suction force (200 mm
The second vacuum jacket c ₂ and the third vacuum jacket c ₃ should be 300 mmHg to 400 mmHg. For these vacuum jackets C, brass is suitable as the material in the same way as cooling jacket B, and the length is preferably about 50 mm, and the installation interval depends on the diameter and wall thickness of the foam pipe to be molded, and the molding speed. Therefore, it can be changed arbitrarily, but usually on the cooling jacket B side.
The length should be about 50 mm, and the length should be gradually increased, and the number of the pieces should preferably be about 2 to 4.

These vacuum jackets C are installed in an atmosphere of spray water as described above, and a sprayer 7 such as a sprayer is installed between each vacuum jacket.
is installed and sprays cooling water onto the foam pipe, creating a uniform water film on the pipe surface and cooling the pipe.

In this way, the foam pipe moves in the atmosphere of spray water while being cooled by the vacuum jacket C while maintaining its perfect circle, and is inserted into the water tank D installed behind the vacuum jacket.

The water tank D is used to further cool the foam pipe and adjust the outside diameter and roundness of the pipe, and not only stores water in the water tank, but also places an adjustment roll 8 and a receiving roll 9 thereon. The adjusting rolls 8 are two rolls that rotate at intervals that match the outer diameter of the pipe, and as shown in FIG. The foamed pipe is made of plastic with a ridge formed thereon to ensure good sliding with the pipe, and the foamed pipe is guided between the recesses 8' by two rolls, and the rotation of these rolls further corrects it to a perfect circle. The rolls are mounted on the support frame 10 so that the spacing can be varied according to the outer diameter of the pipe, and the spacing between the rolls is adjusted by this arbitrary variable means and fixed at a desired spacing using fasteners or the like. For example, the illustrated variable means is such that the lower part of the rotational support shaft 8'' of the roll 8 is attached to a support base 10', the upper part of the rotational support shaft 8' is inserted into a guide groove provided in a support plate 10'', and a stopper 10 is attached. It is fixed, and by moving the support stand 10' left and right, the rotation support shaft 8'' also moves left and right within the guide groove of the support plate 10''.
This variable means is not limited to this,
It can have any shape and structure.

The adjusting rolls 8 are placed in one to several places in the traveling direction in the water tank D to correct the foam pipe into a perfect circle and adjust it to the final perfect circle. The foamed pipe thus adjusted passes over a receiving roll 9 and is taken up by a take-up machine E.

The take-up machine E transfers the molten foam pipe extruded from the extruder A to a cooling jacket B, a vacuum jacket C,
It is taken up via an adjustment roll 8, and may be of any type such as a roller type, belt type, or track type. The point is that it has a structure that allows it to take out a foam pipe formed into a perfect circle.

<Effects> The present invention extrudes a molten foam pipe while supporting the molten resin with an expansion cap attached to the tip of the mandrel of an extruder, cools the pipe with a cooling jacket, and cools the pipe in an atmosphere of sprayed water. Since the material is successively corrected using a plurality of vacuum jackets installed at predetermined intervals in the extrusion direction, and then passed between adjustment rolls installed in a water tank, the desired distance is maintained between the extruder and the cooling jacket. This makes it possible to sufficiently foam the molten resin and prevent drawdown of the molten resin during the foaming process. In addition, although the outside diameter of the pipe is regulated using a cooling jacket, it is difficult to form the pipe into a perfect circle with just that, so a vacuum jacket is used to straighten the pipe to a perfect circle. The molten foam pipe stretches due to the resistance caused by suction and the resistance caused by friction with the inner wall surface of the vacuum jacket, and even if the surface of the pipe is cooled, it takes time for the inside to cool down, so it is easy to become a perfect circle. As mentioned above, it is difficult to install a vacuum jacket long enough to cool the foam sufficiently and form it into a perfect circle. By installing multiple vacuum jackets, it is possible to eliminate elongation due to resistance, and it is possible to straighten the pipe into a perfect circle several times over a long period of time, resulting in a good foamed pipe.

Moreover, since water is sprayed between each vacuum jacket to cool the pipe, a uniform water film is formed on the pipe surface, which reduces the frictional resistance between the vacuum jacket and the pipe surface and reduces the elongation due to pulling. In addition to preventing heat loss from the pipe surface, it has a high efficiency in removing heat from the pipe surface, has a large cooling effect, and reduces deformation due to cooling.

In addition, foamed resin pipes can be formed by sizing using a three-stage effective combination of cooling jacket, vacuum jacket, and adjustment roll, making it easier to size foamed pipes, which was normally considered difficult. It is something.

[Brief explanation of the drawing]

The drawings show an embodiment of the sizing method and apparatus of the present invention, and FIG. 1 is a schematic side view of the entire structure;
Figure 2 is an enlarged side view of the extruder tip die section, Figure 3 is an enlarged sectional view of the cooling and vacuum jacket section,
Fig. 4 is a perspective view of the cooling jacket section, Fig. 5 is a perspective view of the vacuum jacket section, Fig. 6 is a front view of the adjustment roll, Fig. 7 is a side view of the take-up machine, and Figs. 8 and 9 are This is a conventional diagram, in which A is an extruder, a is a mandrel, b is an expansion cap, B is a cooling jacket, C is a vacuum jacket, D is a water tank,
5 is an absorption hole, 7 is a sprayer, and 8 is an adjustment roll.

Claims (1)

[Claims] 1. A molten foam pipe is extruded while supporting the molten resin with an expansion cap attached to the tip of the mandrel of an extruder, and the pipe is cooled with a cooling jacket while being exposed to an atmosphere of spray water. A thermoplastic resin foam pipe characterized in that it is successively straightened using a plurality of vacuum jackets installed at predetermined intervals in the extrusion direction and having a plurality of suction holes in the inner wall, and then passed between adjustment rolls installed in a water tank. Sizing method 2: Attach an expansion cap to the tip of the extruder mandrel, provide cooling jackets sequentially in the extrusion direction, and install multiple vacuum jackets at predetermined intervals, with a large number of suction holes on the inner wall of the vacuum jackets. A cooling sprayer is provided between the cooling jacket and the vacuum jacket, a water tank is provided behind the vacuum jacket, and adjustment rolls are installed in the water tank to rotate at intervals that match the outer diameter of the pipe. Equipment for sizing plastic resin pipes.