JPS6053688B2 - Manufacturing method and sizing die for highly foamed insulation - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in the manufacturing method of highly foamed insulators.

Conventionally, when covering a core material with highly foamed insulation such as polyethylene, the extrusion coating is performed using a mass extrusion device, and the surface is molded with a sizing die at the same time as foaming, resulting in a high quality foamed insulation with a uniform surface. However, there are various technical problems with the sizing die.

For example, if a highly foamed insulator is sized excessively, the frictional resistance when the surface of the highly foamed insulator is rubbed against the inner surface of the sizing die causes the cells in the highly foamed insulator to rupture, causing the bubbles to connect with adjacent ones. A nest occurs.

In order to solve this problem, the inventor invented a method of coating the inner surface of the sizing die with a material such as Teflon, which has a low coefficient of friction, and has already filed a patent application as Japanese Patent Application No. 50-32971. However, even if this method is used, there is a limit, and it is important to avoid excessive friction and to mold with appropriate friction. Conventional sizing dies usually use metal cylinders with good thermal conductivity because sizing needs to be done while being cooled with a cooling medium, but since the inside of the sizing die cannot be seen visually, highly foamed insulators are used to There is no way to know if it has been molded.

In general, in order to mold with moderate friction, it is important to select the inner diameter of the sizing die and determine the separation distance between the extrusion device and the sizing die, and the latter is especially important when it comes to actually extruding the highly foamed insulator and its foaming state. While visually observing the process and adjusting the position to achieve the best sizing, there is a considerable loss in preparation time and materials.
Additionally, if the center axis of the sizing die is not aligned with the center axis of the highly foamed insulator, there will be problems such as the surface of the highly foamed insulator not being smooth or the formation of cavities inside, but this is due to the inclination of the sizing die. This is because the degree of sizing in the circumferential direction on the surface of the highly foamed insulator is not uniform, and in order to eliminate this problem, a considerable amount of time and materials are spent adjusting the center axis of the sizing die. .

In view of the current state of these sizing dies, the present invention aims to provide a manufacturing method that allows adjustment with simpler operations, and detects friction between the sizing die and the highly foamed insulator at two or more locations in the circumferential direction of the inner surface of the sizing die. While attaching the pressure-sensitive elements and measuring the frictional resistance, adjust the distance between the sizing die and the extrusion device or the sizing die so that there is no difference in the frictional resistance of each pressure-sensitive element and the value of the frictional resistance is within the most positive range. This feature is characterized by adjusting the slope of. An embodiment will be explained below based on FIG. 1 showing an embodiment. FIG. 1A is a side view for schematically explaining the present invention, and FIG. 1B is a sectional view taken along the A-A'' cross section, in which 1 is an extrusion device and the core material is supplied by a feeder (not shown). 5 is a highly foamed insulator. Immediately after exiting the extrusion device, the core material is coated with foam, but immediately after leaving the extrusion device, it begins to foam gradually or suddenly into an irregular shape and enters the second sizing die.

The sizing die usually has a cooling medium passage as shown at 3 and is cooled. While being sized with a sizing die, the highly foamed insulator comes into contact with a pressure sensitive element 4 attached to its rear 2''. This pressure sensitive element 4 can detect the frictional force when the highly foamed insulator runs in contact. A known mechanical or electrical strain part is used.
Five of these pressure sensitive elements are attached to the inner surface of the sizing die. Depending on the size of the pressure-sensitive element, the inner surface of the sizing die may be cut to prevent the surface of the highly foamed insulator from becoming a convex portion and to be attached. Also, the first
In the figure, the pressure-sensitive element is attached to the rear ζ part of the sizing die, but it can also be attached to the middle part of the sizing die, or depending on the shape of the pressure-sensitive element, it can be attached in a strip shape in the length direction of the sizing die. It is.

Of course, this pressure sensitive element is not completely integrated with the sizing die, but may be separated to an appropriate degree. Since the frictional resistance between this pressure-sensitive element and the highly foamed insulator is regarded as the frictional resistance between the sizing die and the highly foamed insulator, it is necessary to install several pressure-sensitive elements in the circumferential direction. Installing one is sufficient in most cases. Using these pressure-sensitive elements, the running friction of the highly foamed insulator is detected at two or more locations in the circumferential direction, and the sizing die and extrusion are adjusted so that the difference is small and the value is an appropriate value. Adjust the distance to the device and the position of the center axis of the sizing die.The appropriate friction value described above will be the same as the displayed value at that time depending on the surface condition of the sized highly foamed insulator and the type of pressure-sensitive element. All you have to do is decide.

By doing the above, it is possible to adjust the position of the sizing die while looking at the displayed value regarding the frictional resistance from the pressure-sensitive element, which allows for easy adjustment in an extremely short period of time, and also enables automatic control, which was previously impossible. This has a big effect. Furthermore, if this manufacturing method is applied when an unbiased backcross head is used in the extruder and an insulator with extremely low eccentricity is extruded, the good eccentricity will not be diminished by sizing, and it will be extremely effective. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the manufacturing method according to the present invention, where A is a side view, B is a sectional view taken along line A-A'', 2, 2'' is a sizing die, 3
4 indicates a cooling medium passage, and 4 indicates a pressure sensitive element.

Claims (1)

[Claims] 1. In a method of extrusion manufacturing a highly foamed insulator on a core material, after the core material is extruded and coated with a highly foamed insulator, a pressure-sensitive element is attached to detect friction with the highly foamed insulator. A method for producing a highly foamed insulator, characterized in that frictional resistance is detected by a sizing die, and the position of the sizing die is adjusted according to the displayed value. 2. A sizing die for sizing highly foamed insulators, characterized in that two or more pressure-sensitive elements are attached to the inner surface of the sizing die at the same position as the inner diameter of the sizing die.