JPH0143608B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a die apparatus for blow molding blown film.

Conventionally, when blow molding inflation films, it has been extremely difficult to maintain a constant wall thickness of a thin cylindrical bubble. That is,
The thin film of molten resin discharged from the nozzle hole has uneven thickness due to unevenness of the nozzle hole or uneven temperature of the molten resin near the nozzle. It has an annular shape with uneven thickness, with a thin wall portion b on one side and a thick wall portion c on the other side.

Therefore, the outer peripheral wall that makes up the annular nozzle is
Uneven thickness was prevented by moving the nozzle hole using an adjustment bolt and correcting the unevenness of the nozzle hole.

However, as shown in FIG. 2, when local thickened portions d occur at several locations on the circumference of bubble a, it is not possible to adjust the thickness of the bubble using only the above-mentioned nozzle hole adjustment means. Unbalanced position cannot be corrected.

In order to correct the local unevenness of the wall thickness of the bubble as described above, the present invention includes a plurality of heating units that can be selectively energized on the inside and outside of the nozzle hole. It is an object of the present invention to provide a die device which prevents molten resin from falling and adhering to the lead wires for the unit.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

In FIGS. 3 and 4, 1 is a die;
It is attached to the top surface of an extrusion molding machine (not shown) that supplies molten resin.

The die 1 includes an annular housing 2 and a cylindrical insert 3 inserted into the housing 2. Between the inner peripheral surface 2a of the housing 2 and the outer peripheral surface 3a of the insert 3, there is a , an annular flow path 4 is formed.

An annular adjustment ring 6 is attached to the upper surface of the housing 2 with a plurality of tightening bolts 7, and an annular adjustment ring 6 is inserted so that the upper part of the flow path 4 becomes an annular nozzle hole 5 with a smaller clearance. An annular mandrel 8 is also fixed to the upper surface of the body 3.

An annular notch 2 is provided on the outer periphery of the upper surface of the housing 2.
b is engraved, and a downwardly directed annular wall 6a that can be engaged with the notch 2b is formed protruding from the outer peripheral edge of the adjustment ring 6.

An adjustment bolt 9 is attached to this annular wall 6a from the outside.
is screwed in, the tip of which is in contact with the peripheral wall of the notch 2b, and by adjusting the degree of screwing of the adjustment bolt 9, the width of the nozzle hole 5 can be adjusted in the lateral direction. There is.

The inner circumferential wall surrounding the nozzle hole 5 of the adjustment ring 6 has a thin annular outer lip portion 6b that protrudes upward, and a large number of bottomed holes in the vertical direction are located close to the outer surface of the outer lip portion 6b. circular holes 10 are bored at intervals.

Almost the lower half of an insulated cylindrical heating unit 11 containing a built-in heater is inserted into each circular hole 10.

Reference numeral 12 denotes a lead wire, and by passing a current through this lead wire 12, various parts of the outer lip part 6b are heated independently and individually, thereby selecting a desired part on the circumference of the nozzle hole 5. It is designed to be able to be heated.

On the upper surface of the outer periphery of the mandrel 8, there is an inner lip portion 8a of a thin ring opposite to the outer lip portion 6b.
An annular groove 13 whose top surface is open is carved so as to form an annular groove 13 .

An annular groove 1 is formed adjacent to the inner wall of the inner lip portion 8a.
A large number of vertical circular holes 14 are bored in the bottom wall of 3, and a heating unit 11 similar to that described above is inserted into each circular hole 14.

The inner heating unit 11 and the outer heating unit 11 are arranged in pairs on the same radius, sandwiching the nozzle hole 5, so that the inner and outer heating units 11 that are paired with each other are heated at the same time. ing.

The upper surface opening of the annular groove 13 is connected to an annular packing 15 and a presser plate 1 supported in the middle part of the annular groove 13.
6, and packing 15
The holding plate 16 is attached to the mandrel 8 by a tightening bolt 17 passing through them.

A plurality of vertical exhaust holes 18 are bored near the center of the mandrel 8, and the lower ends of the exhaust holes 18 are connected to an external exhaust blower (not shown) via a passage 19 provided near the center of the insertion hole 3. (omitted).

The annular groove 13 and the passage 19 are connected by a through hole 20, and the lead wire 12 of the heating unit 11 of the inner lip portion 8a passes from below the die 1 to the outside through the through hole 20. It is being pulled out.

In FIG. 3, 21 is a guide tube provided at the center of the mandrel 8 and connected to a supply air blower (not shown) that supplies cooling air.

A cooling air ring is usually attached to the outer periphery of the die 1, but its illustration is omitted.

Next, the operation of the apparatus of the present invention configured as above will be explained.

As shown in FIG. 4, the molten resin e supplied from an extrusion molding machine (not shown) into the flow path 4 is extruded upward from the nozzle hole 5 and is stretched to form a thin cylindrical bubble. do.

If a local thick portion d occurs in this bubble as shown in FIG. 2, the outer lip portion 6a and the inner lip portion 8b are heated in the portion corresponding to the thick portion d, respectively. Rapid heating in unit 11. This heating improves the extensibility of the molten resin and eliminates local thickening.

In addition, in the present invention, the inner heating unit 1
The lead wire 12 of No. 1 is led to the power source through the annular groove 13, the through hole 20, and the passage 19, but the annular groove 13, which is the only exposed part, is closed by the packing 15. The above lead wire 12
Furthermore, there is no possibility that the product will fall and have molten resin adhere to it, thereby shortening its lifespan.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of a bubble for explaining the uneven thickness of the bubble, FIG. 3 is a plan view showing one embodiment of the present invention with half omitted, and FIG. , is an enlarged longitudinal cross-sectional view taken along the line X--X in FIG. 3. DESCRIPTION OF SYMBOLS 1...Die, 2...Housing, 3...Insert, 4...Flow path, 5...Nozzle hole, 6...Adjustment ring, 6a...Outer lip portion, 8...Mandrel, 8a...Inner side Lip portion, 11... heating unit, 12... lead wire, 13... annular groove, 14...
... circular hole, 15 ... packing, 16 ... presser plate,
18... Exhaust hole, 19... Passage, 20... Communication hole, 21... Guide tube, a... Bubble, e... Molten resin.

Claims (1)

[Claims] 1 Comprising an annular housing and an insert inserted into the housing, a thin annular outer lip formed on the inner periphery of the housing, and a thin annular inner lip formed on the outer periphery of the insert. and a plurality of pairs of inner and outer lips, which form an annular nozzle hole, and which are located close to the outer periphery of the outer lip and the inner periphery of the inner lip, and which can be selectively heated at the same time. A heating unit is disposed in the housing and the insert, respectively, and a lead wire for the inner heating unit is led to the heating unit through a through hole provided in the insert and an annular groove provided in the upper surface of the insert. A die device for blown film, characterized in that the annular groove is closed with a gasket.