JPH0725124B2 - Cooling device for resin molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin-molding cooling device used in a foaming resin molding machine to cool a sheet of thermoplastic resin extruded from a mold.

<Prior Art> Conventionally, as a foaming resin molding machine, a material made of a thermoplastic resin is extruded into a tube shape from a circular opening slit of a die by an extruder and cooled by a cooling device, and both sides of the tube are cooled. There is a film or sheet which is cut at a portion and is wound up as two upper and lower films or sheets.

As the above-mentioned extrusion method, there is an upward, downward or horizontal extrusion method, but a horizontal extrusion method (hereinafter referred to as a horizontal extrusion method) is used at the time of extrusion or take-back. Most used because it is easy to handle.

Then, generally, as a cooling method in the horizontal extrusion method, a cooling pipe is internally provided in a cylindrical body directly connected to a mold (hereinafter referred to as a mandrel), and an outer surface of the mandrel is brought into contact with an inner surface of the tube. A so-called inside mandrel system is used in which the tube is cooled and the inner diameter of the tube is regulated to adjust the molding size. Further, a so-called outside mandrel system in which the inner surface of the mandrel is cooled while contacting the outer surface of the tube and the outer diameter of the tube is regulated to adjust the molding size is also used.

<Problems to be Solved by the Invention> By the way, in the above horizontal extrusion method, the air around the mold and mandrel is heated by the heat of the device such as the mold and rises, and the ambient temperature surrounding the mold and the mandrel is increased. In addition, there is a vertical gap (the upper side is increased by about 7 ° C). The difference between the upper and lower ambient temperatures also affects the cooling efficiency of the mandrel, and the molding conditions are different between the upper and lower parts, which causes a difference in the quality of the molded product. In particular, when a primary product such as the above-mentioned film or sheet is reheated and molded to obtain a secondary product, a remarkable difference occurs in the quality of the secondary product.

For example, in polystyrene type, there is a vertical difference in thickness, stretching, etc., and due to the vertical difference in stretching, there is a problem that deep drawing products such as cups and bowls cannot be molded under the same upper and lower conditions. Also, in the polyolefin type as well as in the polystyrene type, due to the influence of the vertical difference in the drawing, the deep drawing cannot be formed under the same conditions in the vertical direction, and the vertical difference in the drawing occurs during the molding of the primary product. Due to the influence, a difference occurs in the thickness of the secondary product, especially when the expansion ratio is 2 times or less and the thickness after molding is 0.5 mm.
In the following primary products, wave fringes are likely to occur on the upper side, and when the expansion ratio is 2 times or more, the slit width of the mold is expanded to prevent the occurrence of wave fringes. In that case, since the difference in the vertical direction of the drawing becomes large, there is a problem that good molding cannot be performed even if other molding conditions (temperature and extrusion speed) are changed.

This invention has been made in view of the above problems,
It is an object of the present invention to provide a resin-molding cooling device that can perform uniform cooling and, in turn, can perform uniform molding using a foaming resin molding machine.

<Means for Solving the Problems> As a resin molding cooling device of the present invention for achieving the above object, an inner surface or a tubular sheet of a thermoplastic resin extruded horizontally from a mold by an extruder or In a resin molding cooling device that cools by contacting the outer surface,
It is characterized in that it is composed of at least two vertically divided cooling bodies, each cooling body being provided with independent cooling fluid paths.

<Operation> According to the resin-molding cooling device having the above-described configuration, since the divided cooling bodies that are at least vertically decomposed into two are provided with independent fluid paths, the temperature and the flow rate of the fluid supplied to each fluid path. By adjusting the above, the cooling performance can be adjusted separately for the upper and lower parts, and the upper and lower temperature difference in the cooling process of the tubular sheet of thermoplastic resin extruded from the mold can be corrected.

<Examples> Detailed description will be given below with reference to the accompanying drawings showing examples.

FIG. 2 is a schematic view showing the entire structure of the foamed resin molding machine (A), which includes an extruder (1) having a raw material hopper (11) and a foaming agent injection hole (12), and the extruder (1). Connected,
A mold (2) having an arcuate slit (not shown),
A cooling and sizing mandrel (3) connected to the mold (2), a cutter (4) provided behind the mandrel (3), and a cutter (4) provided behind the cutter (4). It has a pair of winding rollers (5) and (6) as a main part.

In the foaming resin molding machine (A) described above, in the extruder (1), the raw material (s) of the thermoplastic resin supplied from the raw material hopper (11) is fed through the foaming agent injection hole (12) to the foaming agent (b). And the raw material (s) is extruded by the extruder (1) from the slit of the mold (2) along the outer surface of the mandrel (3) to form a tubular sheet ( After making p), both sides of the tubular sheet (p) are cut by a cutter (4), and the upper and lower two sheets are taken up by take-up rollers (5) and (6).

In addition, the connecting portion (1) between the mold (2) and the mandrel (3)
0) has a taper shape and has an air blowout hole (not shown) for blowing air into the tubular sheet (p) to inflate the tubular sheet (p) to a predetermined size. ing.

As shown in FIG. 1, the mandrel (3) is a cylindrical first mandrel (31), a second mandrel (32) and a third mandrel (3) which are divided into three along the extrusion direction.
3), and the mandrels (31) (32) (33) are divided into upper and lower divided cooling bodies (31a) (31b),
Division cooling bodies (32a) (32b) and division cooling bodies (33a) (3
3b).

Cooling pipes (71a) (71b), which are independent fluid paths, are cast in the respective divided cooling bodies (31a) (31b), and are also installed therein. Similarly, the divided cooling bodies (32a) (32b) are provided. The cooling pipes (72a) (72b) are respectively installed inside, and the divided cooling bodies (33a) (33b) are respectively installed with cooling pipes (73a) (73b). These cooling pipes (71a)
(71b) ... (73b) circulates a heat-exchangeable fluid such as water, oil or air. In addition, each cooling pipe (71
a) (71b) ... (73b) are arranged in a skewed pattern as shown in FIG.

Reference numeral (8) is a vertical plate for positioning the mandrel, which is attached at a position easy to attach. (9) is a spacer interposed between the upper and lower divided cooling bodies (31a) (31b) ... (see FIG. 4), and the spacer (9) is a cooling pipe (not shown) of an independent system. ) May be included, and the temperature may be adjusted independently, or a heat insulating material that blocks heat transfer between the upper and lower divided cooling bodies (31a) (31b).

In addition, as a material of each mandrel (31) (32) (33), a metal such as aluminum or iron or a ceramic can be used, and the surface thereof is coated with a fluororesin (trademark Teflon, manufactured by DuPont), For example, those plated with a metal such as Teflock or Nidax (manufactured by Metal Surface Chemical Co., Ltd.) may be used.

According to this embodiment, the divided cooling bodies (31a) (31b) ...
a) (71b) ...
a) The cooling performance of the mandrel (3) can be adjusted separately by adjusting the temperature and flow rate of the fluid supplied to (71b), and the tubular shape extruded from the mold (2). It is possible to correct the temperature difference between the upper and lower sides of the sheet (p) during the cooling process. Therefore, it is possible to obtain a foamed sheet (primary product) that is homogeneous in the upper and lower parts, and thus to obtain a homogeneous secondary product.

Further, along the horizontal direction, the first mandrel (31)-
Since it is divided into the third mandrel (33), by separately adjusting the cooling performance of these mandrels (31) to (33), it is possible to properly adjust the temperature gradient in the horizontal direction during the cooling process. You can make fine-tuned adjustments according to the type and expansion ratio.

The number of divisions along the mandrel (3) horizontal direction is
It can be increased or decreased depending on the type of resin and the expansion ratio. In addition, the upper and lower split cooling bodies (31) of the mandrel (3)
It is also possible to divide each of a) (31b).

Further, a heat insulating material or the like may be interposed between the mandrels (31) (32) (33), and the spacer (9) does not necessarily have to be provided.

Further, the cross-sectional shape of the cooling pipes (71a) (71b) ... Is preferably a square cross-sectional shape because of high cooling efficiency, but may be another cross-sectional shape such as a circular cross section or an elliptical cross section.

In addition, instead of using a cooling pipe as a fluid passage, a cooling hole formed in a divided cooling body by profile extrusion or the like is used, and a groove formed in an inner circumference or an outer circumference of the divided cooling body is covered with a lid. For example, various design changes can be made without changing the gist of the present invention.

Hereinafter, the present invention will be described in detail based on experimental examples and comparative examples.

<Experimental Example I and Comparative Example I> Experimental Example I Using the foamed resin molding machine and the mandrel (3) as a cooling device for resin molding of the above-mentioned examples, raw material ... Polystyrene DIAMONEX HH102 (polystyrene) as polystyrene (MI = 3.5, catalog value) with 1 part of nucleating agent talc Foaming agent: Inject 3.2% (weight ratio) of butane to the above materials Extruder (1): Cylinder temperature 200 to 90 ° C Extrusion Quantity 60kg / H Mold (2) …… Slit diameter 200mm Slit width 0.7mm Mandrel (3) …… Water is used as cooling fluid, and as shown in Table 1 above, upper and lower cooling pipes (71a) (71b) …
Of the same flow rate, and the upper cooling pipe (71a)
The fluid temperature at the inlet of (72a) is set lower than that at the lower side. Foamed sheet: A foamed sheet as a primary product is manufactured under the molding conditions of a foaming ratio of 11 times and a thickness of 2.3 mm. Secondary molding was performed under the thickness ratio (secondary product / primary product) and molding conditions shown in 1 to obtain a secondary product, and the secondary product was good in terms of elongation and variation in vertical thickness (in Table 1, ○). Marked) or defective (in Table 1 x)
As a result, an excellent evaluation result was obtained.

Comparative Example I On the other hand, under the same conditions as in Experimental Example I, the fluid temperatures at the inlets of the upper and lower cooling pipes (71a) (71b) of the mandrel (3) were set to be the same, whereby the conventional mandrel When a primary product and a secondary product according to Comparative Example I were manufactured by simulating the above, and the same evaluation test as in Experimental Example I was performed, the result was that the elongation was good, but the thickness variation was poor. .

From the evaluation test results of the secondary products respectively obtained in Experimental Example I and Comparative Example I, when the conventional mandrel simulated by Comparative Example I was used, a homogeneous secondary product could not be obtained. It was demonstrated that when the cooling performances of the upper and lower divided cooling bodies (31a) (31b) of the mandrel (3) were separately adjusted as in Experimental Example I, a homogeneous secondary product was obtained.

<Experimental Example II> Using the foamed resin molding machine and the mandrel (3) as a cooling device for resin molding of the above-mentioned embodiment, raw material ... Asty polystyrene stylon 685 (MI = 2.1, catalog value) as polystyrene , High-impact Idemitsu Styrol HT51 (MI = 2.1, catalog value) manufactured by Idemitsu Petrochemical Co., in a weight ratio of 4: 1 and 1 part of nucleating agent talc Foaming agent ... Inject 3.5% (weight ratio) of butane Extruder (1) Cylinder temperature 210-98 ℃ Extrusion amount 63k
g / H Mold (2) …… Slit diameter 200mm Slit width 0.7mm Mandrel (3) …… Water is used as a cooling fluid.
As shown in, the fluid temperatures at the inlets of the upper and lower cooling pipes (71a) (71b) ... are made equal, and the flow rate of the upper cooling pipes (71a) (72a) is set to be higher than that of the lower cooling pipes (71a) (72a). Foamed sheet: A foamed sheet as a primary product is manufactured under the molding conditions of a foaming ratio of 11.5 times and a thickness of 2.4 mm. Further, the thickness ratio (secondary product / primary product) and molding conditions shown in Table 1 Next molding is performed to obtain a secondary product, and the secondary product has good elongation (indicated by ◯ in Table 1) or poorness (indicated by × in Table 1) with respect to variation in thickness in the vertical direction.
As a result, an excellent evaluation result was obtained. This allows the upper and lower cooling pipes (71
a) (71b) ... Even when supplying fluids of the same temperature to the upper cooling pipes (71a) (72a) by increasing the flow rate to that of the lower cooling pipes (71a) (72a). It was demonstrated that the cooling performance of (32a) can be improved more than that of the lower side, and thus a good secondary product can be obtained.

<Experimental Example III and Comparative Example II> Experimental Example III Using the foamed resin molding machine and the mandrel (3) as a cooling device for resin molding of the above-mentioned Examples, raw material ... Nobrene AD-571 as polypropylene
(Sumitomo Chemical Co., MI = 0.6, catalog value)
0.5 times and 5 parts of hydrocerol were added. Foaming agent …… Inject 1% (weight ratio) butane to the above raw material Extruder (1) …… Cylinder temperature 240-125 ℃ Extrusion amount 75
kg / H Mold (2) …… Slit diameter 200mm Slit width 0.5mm Mandrel (3) …… Water is used as cooling fluid.
As shown in, the flow rates of the upper and lower cooling pipes (71a) (71b) are made equal, and the upper cooling pipes (71a) (72a)
The fluid temperature at the inlet of a) is set lower than the following: Foamed sheet: A foamed sheet as a primary product is manufactured under the molding conditions of a foaming ratio of 1.7 times and a thickness of 0.95 mm. Vacuum molding is performed under the thickness ratio (secondary product / primary product) and molding conditions shown in Table 1 to obtain a secondary product, and the secondary product has good elongation (○ in Table 1).
When an evaluation test was performed to judge whether the test result was marked with () or was bad (marked with x in Table 1), good results were obtained.

Comparative Example II On the other hand, under the same conditions as in Experimental Example III, the fluid temperature at the inlets of the upper and lower cooling pipes (71a) (71b) of the mandrel (3) was made the same, so that the conventional mandrel When a primary product and a secondary product according to Comparative Example II imitating the above were manufactured, and the same evaluation test as in Experimental Example III was performed, the elongation was different in the upper and lower directions, and the result was defective.

From the evaluation test results of the secondary molded articles respectively obtained in Experimental Example III and Comparative Example II, when the conventional mandrel simulated by Comparative Example II is used, a homogeneous secondary product cannot be obtained. It was demonstrated that when the cooling performances of the divided cooling bodies above and below the mandrel (3) were separately adjusted as in Experimental Example III, a homogeneous secondary product was obtained.

<Effects of the Invention> As described above, according to the resin-molding cooling device of the present invention, since fluid passages independent of each other are provided in the divided cooling bodies that are divided into at least two portions, the fluid is supplied to each fluid passage. By adjusting the temperature and flow rate of the fluid to be heated, the cooling performance can be adjusted separately for the upper and lower parts, and the upper and lower temperature differences in the cooling process of the thermoplastic resin tubular sheet extruded from the mold can be corrected. Therefore, it is possible to obtain a foamed sheet (primary product) that is homogeneous in the upper and lower directions, and thus it is possible to obtain a homogeneous secondary product.

[Brief description of drawings]

1 is a sectional view of a cooling device for resin molding according to an embodiment of the present invention, FIG. 2 is an overall configuration diagram of a foamed resin molding machine, FIG. 3 is a perspective view, and FIG. 4 is a side view. (1) …… Extruder, (2) …… Mold, (3) …… Mandrel, (31a) (31b) (32a) (32b) (33a) (33b) …… Split cooling body, (71a) (71b) (72a) (72b) (73a) (73b) ... cooling pipe as a fluid path, (p) ... tubular sheet

Claims (1)

[Claims] 1. A resin molding cooling device for cooling by contacting an inner surface or an outer surface of a tubular sheet of a thermoplastic resin extruded in a horizontal direction from a die by an extruder,
A resin molding cooling device comprising a divided cooling body which is divided into at least two parts in an upper and lower direction, and each divided cooling body is provided with an independent cooling fluid path.