JPH058119Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to an improved mandrel suitable for obtaining a cylindrical stretched sheet or film of thermoplastic resin having a uniform thickness and preventing uneven stretching.

(Prior art and its problems) Conventionally, in a method for manufacturing a cylindrical biaxially stretched sheet or film of thermoplastic resin, a cylindrical sheet or film extruded by an annular die is guided to an air inflation or stretching mandrel,
An apparatus is employed which stretches the sheet or film in the transverse direction and simultaneously stretches it in the longitudinal direction by adjusting the speed ratio between the nip rolls.

That is, such a mandrel-type biaxial stretching device mainly includes a feeding roll, a (mandrel) preheating section,
(Mandrel) Consisting of a heated stretching section and a take-up roll, the cylindrical sheet or film extruded from an annular die directly connected to the extruder, or the stretched sheet or film obtained by uniaxially stretching the sheet or film, is produced by the mandrel preheating section. After being preheated in the mandrel heating and stretching section, it is stretched in the transverse direction and at the same time in the longitudinal direction (quickly cooled by a water-cooled or air-cooled cooling ring).
It is a structure that is taken over by trading rolls.

However, when a cylindrical sheet or film of a thermoplastic resin, especially a thermoplastic resin containing a large amount of inorganic filler, is biaxially stretched using a mandrel-type stretching device having the above-described structure, the resulting sheet or film becomes thinner. It tends to cause unevenness, wrinkles occur when the product is rolled up, and unevenness tends to occur on the rolled sheet. In addition, for example, when printing on such materials, thick areas may be printed darkly, but thin areas may become unclear, resulting in uneven printing, or wrinkled areas may not be bonded together during lamination, reducing product value. . Another drawback is that thinner parts have weaker strength and may break.

(Means for Solving the Problems) In view of the above, the inventors of the present invention have conducted intensive studies on a mandrel-type biaxial stretching apparatus suitable for producing a cylindrical stretched sheet or film of uniform thickness. As a result, by locally heating or cooling the sheet or film in the stretching part of the mandrel according to the thickness unevenness, the thickness unevenness can be easily corrected (corrected) and a cylindrical stretched sheet with a uniform thickness can be easily produced. They discovered that this can be achieved and proposed the present invention. That is, the present invention provides a cylindrical sheet or film stretching mandrel comprising a cylindrical preheating section and a stretching section having a diameter larger than that of the preheating section. This drawing mandrel is characterized in that it is divided into sections and is provided with a local heating and/or cooling mechanism for the outer periphery that can heat and/or cool each divided section to a different temperature.

Hereinafter, the present invention will be explained in detail based on the drawings, but the present invention is not particularly limited to the following drawings.

FIG. 1 is a typical embodiment of the present invention, and is a schematic diagram showing an apparatus in which a cooler is provided in the mandrel stretching section. Further, FIG. 2 is a schematic diagram showing the manufacturing process of a cylindrical stretched sheet or film using the apparatus of the present invention, and FIG. 3 is a diagram showing the main part of FIG. 1.

A biaxially stretched sheet or film using the apparatus of the present invention is generally manufactured by the process shown in FIG. That is, a cylindrical sheet or film of thermoplastic resin extruded from an annular die 2 directly connected to an extruder 1 is cooled by a cooling mandrel 3 and taken off by a take-up roll 4.

The cylindrical sheet or film may be extruded separately, then wound up and sent out from a new feeder, or the extruded cylindrical sheet may be uniaxially stretched and subjected to the apparatus of the present invention (this step is not shown). figure). The cylindrical sheet or film A, which is flattened and supplied from the take-up roll 4, is supplied to the mandrel via guide rolls 5, 5', 5'', 5, a mandrel suspension device 6, and a mandrel delivery roll 7. The sheet or film A fed from the mandrel feed roll 7 is placed over the mandrel preheating section 8 and stretched in the transverse direction in the mandrel heating and stretching section 9, and also lengthwise due to the speed difference between the feed roll 7 and the take-up roll 11. (cooling ring 10 (water-cooled or air-cooled)
It is quickly cooled down and taken off by a take-up roll 11). Of course, the mandrel preheating section 8 and the mandrel heating and stretching section 9 are provided with heating equipment 12 such as a preheating infrared heater or a high frequency heater. In general, the mandrel-type biaxial stretching device is a general term for each device after the mandrel suspension tool 6 in the process shown in FIG. Roll 11 (and cooling ring 10)
It mainly consists of.

The mandrel of the present invention has a stretching section 1 shown in FIG.
A local heating and/or cooling mechanism 14 for the outer periphery is attached to the outer periphery of No. 3, which is capable of dividing one circumference of the outer periphery into a plurality of parts and heating or cooling each divided part to a different temperature. By operating the local heating and/or cooling mechanism 14, the thickness (stretching) unevenness of the cylindrical sheet or film can be easily corrected. That is,
Depending on the occurrence of wrinkles and sagging in the product sheet or film after biaxial stretching, or by actually measuring the thickness in the width direction, the temperature of the stretched portion corresponding to the portion is determined by the above-mentioned local heating and/or cooling mechanism. Since the thickness can be controlled arbitrarily, the thickness of the product sheet or film can be easily modified (controlled). For example, if a part of a product sheet or film has a thin part, the thickness can be increased by cooling the part of the stretching part corresponding to that part, or by heating the other parts. This allows the thickness to be reduced. On the other hand, if a thick portion occurs in a part of the product sheet or film, the reverse operation may be performed.

The type, shape, and attachment method of the local heating and/or cooling mechanism 14 used in the present invention are not particularly limited as long as it can be operated as described above. For example, a small heater is used as the heating mechanism, and a cooling fan using gas (air) as a refrigerant is used as the cooling mechanism. The local heating and/or cooling mechanism must have a structure that can locally heat or cool the stretched sheet or film, and the means for this is not particularly limited, but a small heater or cooling fan may be used to stretch the stretched sheet or film. The basic method is to install a plurality of heaters or cooling fans around the outer periphery of the section 13 and operate a heater or cooling fan near the location where thickness correction of the sheet or film is required. As a typical embodiment, a mode in which a cooling mechanism is attached to the outer periphery of the extending portion 13 will be explained based on FIGS. 1 and 3. The apparatus shown in FIGS. 1 and 3 has a structure in which a ring 15 containing a plurality of coolers (cooling fans) is attached to the outer periphery of an extending portion 13, and the ring 15 is connected to joints 16, 16 connected to the cooling ring. ’ is fixed. According to the device having such a structure, the thickness can be easily controlled by operating the cooling fan at the location where the thickness needs to be controlled. The cooling medium at this time is air from the gas (air) supply ports 17, 17'.

As long as the present invention satisfies the above-mentioned requirements, other conditions such as the material shape and structure of the other parts constituting the mandrel, the type of composition constituting the sheet or film, or the forming (stretching) conditions, etc. Not restricted. In addition, the method of controlling film thickness is basically to visually observe the shape of the product sheet or film, confirm the position where stretching unevenness occurs, and then install a heater or cooler on the outer periphery of the stretching part corresponding to the position. These operations can be performed manually or automatically by detecting the thickness in the width direction.

(Effects) As described above, according to the apparatus of the present invention, stretching unevenness can be corrected quickly and extremely easily, and a cylindrical stretched sheet or film of uniform thickness can be obtained.

(Examples) Examples of the present invention will be shown below, but the present invention is not limited to the following examples.

Example 1 Polypropylene powder with Ml=1.5 (Tokuyama Soda Co., Ltd.)
(manufactured by Shiraishi Calcium Co., Ltd., trade name: Whiten B), 60 parts by weight of calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd., trade name: Whiten B), and a small amount of a dispersant and a stabilizer were mixed and pelletized.
The pellets are processed using a 30mmφ extruder to adjust the resin temperature to
237℃, resin pressure 250Kg/m ² , screw rotation speed
Extrude the cylindrical sheet at 43rpm, take-up speed 3m/
A cylindrical sheet with a sheet thickness of 200 μm was obtained at min.

Furthermore, this cylindrical extruded sheet was stretched at a stretching temperature of 140°C and a stretching ratio of 1.7 in the transverse direction using the stretching apparatus shown in Fig. 1.
The film was stretched at a stretching ratio of 2.4 times in the longitudinal direction.

At this time, small fans were attached to eight locations corresponding to the outer periphery of the stretching section of the stretching device, and the thickness of the sheet was adjusted by controlling the air volume of the fans.

Accuracy = Maximum thickness - Minimum thickness / Average thickness x 2 x 100 The accuracy determined by the above formula was 6.1%, which was better than when no thickness adjustment using a fan was performed (12.2%).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a typical example of the device of the present invention, and FIG. 3 shows its main parts. Moreover, FIG. 2 is a schematic diagram showing the manufacturing process of a cylindrical stretched sheet or film using the apparatus of the present invention. In the figure, 1 is an extruder, 2 is an annular die, 3 is a cooling mandrel, 4 is a take-up roll, 5, 5', 5'', 5
is a guide roll, 6 is a mandrel suspension device, 7 is a mandrel feeding roll, 8 is a mandrel preheating part,
9 is a mandrel heating stretching part, 10 is a cooling ring,
11 is a take-up roll, 12 is a heating equipment, 13 is a stretching section, 14 is a local heating or/and cooling mechanism, 1
5 is a ring, 16 and 16' are joints, and 17 and 17' are gas supply ports.

Claims (1)

[Scope of utility model registration request] In a mandrel for stretching a cylindrical sheet or film comprising a cylindrical preheating part and a stretching part having a larger diameter than the preheating part, on the outer periphery of the stretching part of the mandrel, one circumference of the outer periphery is divided into a plurality of parts, A stretching mandrel characterized in that a local heating and/or cooling mechanism is attached to the outer periphery that can heat and/or cool each divided portion to a different temperature.