JPH071548A - Metal mold for extrusion molding of thick wall synthetic resin plate - Google Patents

Abstract

PURPOSE:To provide a metal mold for extrusion molding of a thick wall synthetic resin plate wherein even for a thick wall rigid vinyl chloride resin plate, extrusion molding can be excellently carried out by controlling sufficiently occurrence of burn, occurrence of residual thermal stress, etc. CONSTITUTION:A contact cooling piece 4 is provided over all width of a lip at a center vertically between the upper and lower lips in a metal mold for extrusion molding of a synthetic resin plate containing successively a manifold 15, a chalk bar 3, and the upper and lower lips 21 and 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for extrusion molding a synthetic resin plate, and is particularly useful for extruding a thick hard vinyl chloride plate.

[0002]

2. Description of the Related Art In the production of synthetic resin sheets, the extrusion molding method is more continuous than the calendering method, the press working method, etc., and has excellent manufacturing efficiency and simplification of the working process. It has advantages such as obtaining
It has become the mainstream method of manufacturing gats.

In order to manufacture a synthetic resin sheet by this extrusion molding method, a sheet-shaped synthetic resin extruded from a sheet molding die is passed through a polishing roll to polish and polish. The sheet-like synthetic resin coming out of the roll is transferred in a traveling roll group in a cooling zone, and is cooled and solidified by natural cooling during the transfer, and is cooled and solidified.
The synthetic resin is collected by a roll.

As the above-mentioned sheet forming die, a fishtail die and a T-type manifold die are often used. This T-type manifold die has a manifold, a choke bar, and upper and lower lips in order from the resin inflow side, and the inflow resin spreads in a fan shape around the resin inflow point. It is spread in the width direction (direction of the sheet width), passes directly below the choke bar, passes between the upper and lower lips, and is pushed out from the lip tip.
The adjustment of the gap just below the choke bar promotes the widthwise spreading of the resin in the manifold.

[0005]

Between the upper and lower lips of the T-shaped manifold die, the resin channel width is wide, the channel sectional area is large, and the resin flow velocity is low. Strict temperature control is necessary to prevent burning.

However, in the case of a thick plate, the distance between the upper and lower lips becomes considerably large, and the resin at the central position between the upper and lower lips retains heat and becomes hotter than the resin on the inner surface of the lip. Is inevitable. Then, if the lip temperature is adjusted with the resin temperature on the side in contact with the inner surface of the lip as a reference, resin burnt is likely to occur in the central portion of the thickness, and the discoloration due to this burn can be seen through the plate surface. If the lip temperature is adjusted on the basis of the temperature, the temperature of the resin in contact with the lip becomes too low and the surface is apt to be roughened. In any case, extrusion molding of a synthetic resin plate having a good appearance is difficult.

Further, when the product plate thickness becomes thicker, in the above cooling zone, the cooling rate at the central portion of the thickness of the plate-shaped resin becomes significantly slower than the cooling rate at the surface side, and the cooling rate in the thickness direction becomes smaller. Due to the synergistic effect of non-uniformity and non-uniformity of the resin temperature in the vertical direction between the above-mentioned lips, the residual thermal stress becomes remarkable, and the disadvantage that the dimensional deformation during secondary processing, for example, during welding becomes significant. There is also.

An object of the present invention is to extrude a thick synthetic resin plate which is capable of excellently extruding even a thick hard vinyl chloride resin plate while suppressing the occurrence of burning and residual thermal stress. It is to provide the mold.

[0009]

A thick synthetic resin plate extrusion molding die of the present invention is a synthetic resin plate extrusion molding die having a manifold, a choke bar and upper and lower lips in order. A contact cooling element is provided over the entire width of the lip in the upper and lower centers between the lips.

[0010]

The fluid resin between the upper and lower lips, which has a slow resin flow velocity, is temperature-controlled not only on the inner surface side of the lip but also on the inner side of the thickness. Even if the distance between the upper and lower lips is large, the fluid resin between the upper and lower lips is large. Temperature is sufficiently uniformized in the thickness direction.

Therefore, by setting the uniform temperature to an appropriate temperature at which no resin burn occurs and no surface unevenness occurs, a thick synthetic resin plate having a good appearance can be extruded.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1A is a longitudinal cross-sectional explanatory view showing an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line B-B in FIG.

1 (a) and 1 (b), 11 is an upper mold and 12 is a lower mold, which is provided with a flange 13 connected to the barrel of the extruder, and has a resin inlet 14 and a manifold. It has a field 15. Reference numeral 21 is an upper lip attached to the tip side of the mold, and 22 is a lower lip. At least one of the both lips 21, 22 can be finely adjusted in the vertical position by a vertical position adjusting bolt, but its structure is not shown. Reference numeral 23 is a side piece attached to both ends of the upper and lower lips 21 and 22.

3 is an upper mold, a manifold 15 and a lip 2
It is a choke bar provided at an intermediate position between 1 and 2. Reference numeral 4 denotes a contact cooler provided in the upper and lower center between the upper and lower lips 21 and 22 over the entire width of the lip, and a bar having a cooling passage 41 therein is provided across the resin flow path between the upper and lower lips 21 and 22. It penetrates through the side piece 23, and its cross-sectional shape has an acute angle on both the front side and the rear side in order to perform a rectifying action.

To extrude a synthetic resin plate using the above-mentioned mold, the choke bar 3 is adjusted to adjust the choke bar.
3 Adjust the gap immediately below to spread the resin from the extruder in the mold width direction in the manifold 15, and set the upper and lower lips 21,
Turn it over the entire width of the resin flow path between the 22 and the upper and lower lips 21,2.
Extrude in a plate shape from the tip between the two.

In this case, the cross sectional area of the resin flow path between the upper and lower lips 21 and 22 is made significantly wider than, for example, the cross sectional area of the resin flow path before the manifold, so that the upper and lower lips 2 are
The resin flow velocity in the resin flow path between the first and the second is low, and the temperatures of the upper and lower lips 21 and 22 and the temperature of the contact cooler 4 are adjusted so that resin burn does not occur even under such a resin flow velocity. Proceed with extrusion molding.

In the conventional mold, the resin burn is prevented only by adjusting the temperature of the upper and lower lips, but when the product plate thickness is large, the thickness of the resin flow path between the upper and lower lips becomes large,
Even if the temperature of the resin in contact with the lip surface is set to the burn-prevention temperature, the resin temperature at the center of the resin flow path thickness becomes considerably higher than the resin temperature at the lip surface, so in the case of a vinyl chloride plate, It is difficult to avoid burning in the middle of the thickness, and it is inevitable to use expensive resins such as chlorinated vinyl chloride.

However, in the mold of the present invention,
The temperature of the resin can be adjusted by the contact cooler 4 even at the center of the thickness of the resin flow path between the upper and lower lips 21, 22, and the temperature of the resin in contact with the lip surface is set to the burn-prevention temperature. Up and down lip 4 by temperature adjustment by child 4
The temperature at the center of the thickness of the resin flow path between Nos. 1 and 42 can also be set to the burning prevention temperature, and even a thick vinyl chloride plate can be extruded without burning.

As described above, the upper and lower lips 21, 22
The plate-shaped resin extruded from the tip of the gap is passed through a polishing roll, then sent to a cooling zone and transferred by a running roll, and then taken by a take-up roll and fixed by a cutter. Cut the shaku.

During the transfer by the traveling roll, the plate-shaped resin is cooled by air cooling and solidified in front of the take-up machine to a hardness that can withstand the compressive force of the take-up machine. In the cooling and solidifying process of the plate-like resin in the cooling zone, the surface cooling rate is higher than the cooling rate inside the thickness, so that the generation of residual thermal stress is unavoidable, but the cooling zone The larger the temperature difference between the central portion of the thickness of the plate-shaped resin and the surface at the inlet, the larger the residual thermal stress.

That is, in the process of generation of residual thermal stress in the plate-shaped resin, when the outer surface side is cooled and contracted and solidified, the inner side is in a heat softened state and is soft, so that stress is generated despite the cooling contraction of the outer surface side. However, at the time of cooling shrinkage solidification of the inside after cooling shrinkage solidification of the outside surface (shrinkage amount α), since the outside surface is already solidified, stress is generated and this stress state is maintained mechanically. This can be explained by the fact that the higher the temperature of the central portion of the thickness of the plate-shaped resin at the cooling zone inlet, the larger the contraction amount α at the time of cooling contraction and solidification on the inner side, and the larger the stress. . Therefore, by using the mold of the present invention, the resin can be cooled even in the center of the resin flow path between the upper and lower lips, and therefore the temperature of the central portion of the thickness of the plate-shaped resin at the cooling zone inlet can be reduced to the conventional one. It is possible to reduce the residual thermal stress because it is possible to lower the residual thermal stress.

[0022]

The thick synthetic resin plate extrusion molding die of the present invention has the constitution as described above, and the resin temperature can be adjusted not only in the upper and lower lip surfaces but also in the central portion of the thickness between the upper and lower lips. Even if the product plate is thick, the resin can be extruded at a temperature that is sufficiently uniform in the thickness direction. By setting this uniform temperature to an appropriate temperature to prevent resin burn, In the case of, extrusion molding can be performed with good quality without resin burning.

Further, even with a thick synthetic resin plate, the occurrence of residual thermal stress in the cooling process of the cooling zone can be well suppressed, so that even with a thick wall, it is possible to carry out secondary processing such as welding. It is possible to extrude a synthetic resin plate that ensures good dimensional stability.

[Brief description of drawings]

1A is a cross-sectional explanatory view showing an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line A-B in FIG.

[Explanation of symbols]

 15 Manifold 21 Upper lip 22 Lower lip 3 Choke bar 4 Contact cooler

Claims (1)

[Claims] 1. A synthetic resin plate extrusion molding die having a manifold, a choke bar, and upper and lower lips in order, wherein a contact cooler is provided at the upper and lower centers between the upper and lower lips over the entire width of the lips. A mold for extrusion molding thick-walled synthetic resin plates.