JP2000062000A - Mouthpiece for thermoplastic resin film and manufacture of thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the temperature of a mouthpiece in its width direction uniform by inserting at least one heat pipe in the width direction of a mouthpiece in which a thermoplastic resin is molded in a sheet or film shape. SOLUTION: At least one heat pipe is inserted in the width direction of a mouthpiece at a land part molded to be a sheet shape after a resin is expanded in the width direction. The insertion of the heat pipe into the mouthpiece makes the temperature of the mouthpiece uniform. The insertion direction is fitted with the width direction of the mouthpiece, thereby reducing the temperature difference between the central portion and the edge portion of the mouthpiece. It is desired the number of the inserted pipe be generally about 2-20, since more pipes increase the effect of uniform temperature. The resin transferred to the mouthpiece is molded to be a sheet shape through the mouthpiece in which the heat pipe is inserted, and discharged. Use of the mouthpiece achieves the smaller temperature range in the width direction and the excellent thick controlling property in the width direction, so as to obtain a film with smaller thickness uniformity in the width direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for a thermoplastic resin film for molding a thermoplastic resin into a sheet or film and a method for producing a thermoplastic resin using the die.

More specifically, the present invention relates to a die having a high temperature homogeneity in the width direction of a resin discharged from a die in a film shape and a method for producing a thermoplastic resin using the die.

[0003]

2. Description of the Related Art When molding a thermoplastic resin into a sheet or film, the resin is heated and melted by an extruder to remove foreign matters through a filter, etc., and then molded and discharged into a sheet or film with a die. Generally, a method of solidifying on a cooling roll is performed.

The temperature of the resin discharged from the die is preferably as uniform as possible in the width direction. If the resin temperature has a distribution or unevenness in the width direction of the die, the melt viscosity of the resin changes depending on the temperature, so the resin flow rate changes depending on the temperature, and the thickness in the width direction changes. Uniformity will be impaired. On the contrary, by utilizing this property, a number of heaters are installed at the tip of the die, and the temperature profile of the heater is controlled while adjusting the width profile of the film while controlling the temperature of the heater in-line. The technology to do is put to practical use. However, usually, a large number of bolts are provided at the tip of the die, and the push-pull of the bolt is controlled from the obtained thickness profile,
The method of adjusting the lip interval of the base is common. In this case, the push / pull control of the bolt is generally controlled by the thermal expansion of the heater embedded in the bolt, so the heat of the heater is transmitted to the mouthpiece, and the thickness is simply adjusted by adjusting the lip interval. Not only is it changed, but it is difficult to control due to the influence of temperature factors.

There are various types of die such as a T die, a coat hanger die, and a fish tail die, and in any of the die, the resin contained in the die is spread in a width direction to a required width and discharged. It has a function. Therefore, in particular, the resin discharged from the end portion of the die is discharged through a longer flow path than the resin discharged from the central portion. That is, it is easily affected by the base temperature,
Particularly, if the die has a temperature distribution, the temperature change becomes large, which is not preferable. By the way, in order to reduce the temperature distribution of the mouthpiece, a method of making the temperature of the mouthpiece even by floating the heater of the mouthpiece and biting the air layer or the heat medium layer is adopted, but the sufficient effect is still not achieved. Has not been obtained.

On the other hand, attempts have been made to equalize the temperature by inserting a heat pipe using naphthalene as a working fluid into the die, but it has practically no effect and is hardly used.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and achieve temperature equalization in the width direction of a die.

[0008]

That is, the present invention is characterized in that in a die for molding a thermoplastic resin into a sheet or film, at least one heat pipe is inserted in the width direction of the die. And a method for producing a thermoplastic resin film using the die.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

As the die in the present invention, various die such as T die, coat hanger die, fish tail die can be used, and in any die,
It has a function of spreading the resin contained in the die in the width direction to a required width and discharging the resin. In the present invention, at least one heat pipe needs to be inserted in the width direction of these caps. As a form of insertion, it is preferable to insert horizontally at a distance of 1 cm or less from the resin flow path of the die. Particularly preferably, it is preferable to insert the resin into the land portion formed in a sheet shape after being spread in the width direction. Further, the length is preferably the same as the width of the resin flowing in the width direction of the die. The heat pipe referred to here is mainly a metal pipe that is filled with water, naphthalene, etc. under vacuum as a working fluid.
On the other hand, a medium such as a wire mesh called a wick is provided on the inner wall of the pipe so that the working fluid is transported by the capillary phenomenon. When the temperature distribution is provided in the heat pipe, the working fluid is vaporized so that the working fluid is in a gas-liquid equilibrium state at the temperature in the high temperature portion, the internal pressure is increased, and the gas is transported to the low temperature portion where the pressure is low. Next, in the low temperature part, the liquid that has been liquefied and increased to the gas-liquid equilibrium state at that temperature is transported to the high temperature part by the capillary phenomenon in the wick. Since the latent heat of vaporization of the working fluid is consumed and released during the vaporization and liquefaction, the heat is efficiently transported as the fluid moves.
That is, not only the heat conduction of the metal but also the heat transport medium having a larger heat transport ability, the temperature equalizing effect is obtained at every position of the heat pipe.

Here, it is preferable that the working fluid of the heat pipe of the present invention is substantially water. The term “substantially water” as used herein refers to a solution containing 90% by weight or more of water, and may contain alcohol, a water-soluble metal salt, or the like. However, pure water is particularly preferable. As a working fluid of a conventional heat pipe, 200
Water is used as a working fluid in a low temperature range such as ℃ or less. Since water has a large latent heat of vaporization, it is possible to create a very efficient heat pipe. However, when it is used at a temperature exceeding 200 ° C., the internal pressure of the heat pipe becomes very high, and it is difficult to produce a heat pipe having such a pressure resistance. In such a temperature range, naphthalene is used. Was often used as a working fluid. However, when naphthalene is used, it works effectively in a temperature range exceeding 350 ° C., but its operability is poor in a temperature range of 200 ° C. to 350 ° C., and heat transfer efficiency is poor. Therefore, a die used for extrusion of a main thermoplastic resin cannot be used for temperature equalization by a heat pipe because it is used in such a temperature range. However, in recent years, it has become possible to produce a heat pipe using an alloy material of copper and nickel and using water that can be used up to about 350 ° C. as a working fluid. Therefore, by inserting this water-based heat pipe into the die, it is possible to make the temperature of the die uniform. In particular, it is preferable that the inserting direction is set in the width direction of the die because the temperature difference between the central portion and the end portion of the die can be reduced. The number of inserts is not particularly limited, but the more the number is, the higher the temperature equalizing effect is, but the higher the number is, the higher the cost is. Therefore, generally, about 2 to 20 are preferable.

Further, it is also preferable that the base has a resin cooling function. Generally, in an extruder, in order to eliminate unmelted resin, it is common to melt at a temperature considerably higher than the melting point of the resin. However, due to the high temperature, heat deterioration of the resin is likely to occur, and on the other hand, the melt viscosity of the resin is low, and thus the thickness unevenness due to the influence of disturbance on the resin discharged from the die,
In particular, there is a problem that the thickness unevenness in the longitudinal direction of the film is aggravated. Therefore, the extruder melts at a high temperature, cools the die while preventing the generation of unmelted matter, increases the melt viscosity of the resin discharged from the die, and reduces uneven thickness due to disturbance. Here, when the resin is cooled by the mouthpiece in this way, the end portion of the mouthpiece tends to be excessively cooled due to the larger heat radiation, and particularly the effect of temperature equalization by inserting the heat pipe is high. Will be things. Also,
As a method for cooling the resin with the die, a method in which holes are provided in the die and a cooling medium such as air is made to flow can be adopted. Of course, the temperature is not limited to air, and it is also possible to flow temperature-controlled oils for cooling.

In the present invention, in producing the thermoplastic resin film, the thermoplastic resin is heated and melted in an extruder. The extrusion temperature at this time is preferably a low temperature above the melting point of the resin, within the range where no unmelted material remains. Next, the molten thermoplastic resin is sent to the die through a polymer tube or the like, but it is also preferable to pass it through a filter for removing foreign substances in the process. It is also preferable to provide a fixed amount supply device such as a gear pump in order to quantify the discharge amount.

The resin thus delivered to the die is molded into a sheet through the die having the heat pipe of the present invention inserted therein, and is discharged. By using the die of the present invention, since the temperature distribution in the width direction is small and the thickness controllability in the width direction is good, it is possible to obtain a film with small thickness unevenness in the width direction. Further, since the thickness unevenness in the width direction is reduced, a film having a small thickness unevenness in the longitudinal direction can be obtained as a result.

Further, it is also preferable to cool the resin in this die. The temperature at this time may be equal to or lower than the melting point of the resin, and if the temperature is lower than the crystallization temperature, the so-called supercooled state in which the liquid state is maintained without crystallizing and solidifying is preferable. In particular, by cooling to below the melting point, the melt viscosity of the resin is greatly increased, so that the occurrence of thickness unevenness due to disturbance is suppressed, which is more preferable. This resin can be cooled by various devices, but it is preferable in view of its cooling efficiency to provide a hole in the vicinity of the resin flow path of the die and allow a cooling medium such as air to flow.

The thermoplastic resin usable in the present invention includes polyolefin resins such as polyethylene, polypropylene and polymethylpentene, polyamide resins such as nylon 6 and nylon 66, polyethylene terephthalate, polybutylene terephthalate and polyethylene-.
Polyester resins such as 2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate, as well as polyacetal resins and polyphenylene sulfide resins can be used. In particular, in the present invention, polyethylene terephthalate and polyethylene-2,6-
Naphthalate and the like are preferable because of high effect of the present invention. Further, these resins may be homo resins, and may be copolymers or blends. In addition, various additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, and inorganic particles may be added to these resins.

Further, the resin discharged from the die according to the present invention can be cast on a cooling roll and solidified and molded. At this time, if the resin is brought into close contact with the cooling roll by using electrostatic force, the resin It is more preferable because the moldability is enhanced.
It is also preferable that the resin thus obtained is stretched in the longitudinal direction and / or the width direction to obtain a stretched film. Particularly in the case of a biaxially stretched film, the demand for reduction of defects is very strong, and the effect of the present invention can be further enhanced.

[0018]

[Evaluation method of physical properties] 1. Seiko Denshi Kogyo Co., Ltd. robot DSC "RDC220" was used as the melting point and temperature drop crystallization temperature differential scanning calorimeter, and the company's disk station "SSC / 520" was used as the data analyzer.
0 "was used to melt and hold about 10 mg of a sample on an aluminum pan at 300 ° C for 5 minutes, quenching and solidifying with liquid nitrogen, and then raising the temperature from room temperature at a heating rate of 20 ° C / minute. The melting endothermic peak temperature observed at this time was defined as the melting point Tm.
Further, when the sample was melt-held at 300 ° C. for 5 minutes and then cooled at a temperature lowering rate of 20 ° C./minute, the observed temperature-falling crystallization exothermic peak temperature was defined as the temperature-falling crystallization temperature Tc.

2. Resin temperature The resin temperature was measured by forming a hole into which a rod-shaped thermocouple was inserted at the desired measurement point, inserting the thermocouple, and providing a seal to prevent leakage of the resin. The resin temperature immediately after being discharged from the die was measured by inserting a thermocouple into the resin directly discharged. Five points were measured at equal intervals in the die width direction, and the difference between the highest temperature and the lowest temperature was defined as the temperature distribution in the width direction. At this time, it is practically preferable that the temperature distribution is 5 ° C. or less.

3. Film thickness unevenness in the longitudinal direction Anritsu Corporation film thickness tester “KG6
01A "and an electronic micrometer" K306C ", the thickness of the film sampled in the longitudinal direction of the film to a width of 30 mm and a length of 10 m is continuously measured. The transport speed of the film was 3 m / min. From the maximum thickness Tmax (μm) and the minimum value Tmin (μm) at a length of 10 m, R = Tmax−Tmin is obtained, and from the average thickness Tave (μm) of R and the length of 10 m, the thickness unevenness (%) = R / Tave It was determined as x100. It is practically preferable that the thickness unevenness is 5% or less.

[0021]

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 was used as the thermoplastic resin. The melting point Tm measured using DSC was 255 ° C., and the temperature-falling crystallization temperature Tc was 190 ° C. 18 pellets of this polyethylene terephthalate
It was vacuum dried at 0 ° C. for 3 hours, supplied to an extruder, extruded in a molten state at 280 ° C., filtered through a filter, and then supplied to a die whose temperature was controlled at 280 ° C. through a gear pump. A total of eight heat pipes using water as a working fluid were inserted into the mouthpiece in the width direction. The surface temperature of the film extruded from the die in a sheet shape is 25 ° C while applying static electricity.
The film was rapidly cooled and solidified on the casting drum kept at 100 ° C. to obtain an unstretched film having a thickness of 100 μm.

Table 1 shows the temperature distribution in the width direction of the resin discharged from the die and the thickness unevenness of the obtained film. The film had a small temperature distribution in the width direction and a small thickness unevenness. .

Comparative Example 1 The resin was supplied in the same manner as in Example 1 except that the heat pipe was discharged without inserting the heat pipe into the die.

Table 1 shows the temperature distribution in the width direction of the resin discharged from the die and the thickness unevenness of the obtained film. The film has a large temperature distribution in the width direction and a large thickness unevenness. .

Comparative Example 2 Resin was supplied in the same manner as in Example 1, except that a heat pipe having naphthalene sealed in a die was inserted and discharged.

The temperature distribution in the width direction of the resin discharged from the die and the thickness unevenness of the obtained film are shown in Table 1. The results are almost the same as in Comparative Example 1, and the heat pipe filled with naphthalene works at this die temperature. Not considered.

Example 2 The resin was supplied in the same manner as in Example 1, except that holes were provided in the die in the vicinity of the resin flow path and air was passed to cool the resin. The average temperature of the resin discharged from the die was 250 ° C.

The temperature distribution in the width direction of the resin discharged from the die and the thickness unevenness of the obtained film are shown in Table 1. The film has a small temperature distribution in the width direction and a very small thickness unevenness. there were.

Comparative Example 3 As in Example 2, the resin was supplied to the die and cooled by the die. However, the heat was discharged without inserting the heat pipe into the base. The average temperature of the resin discharged from the die was 250 ° C.

Table 1 shows the temperature distribution in the width direction of the resin discharged from the die and the thickness unevenness of the obtained film. The film has a very large temperature distribution in the width direction and a large thickness unevenness. there were.

Example 3 As in Example 2, the resin was supplied to the die and cooled by the die. However, the average temperature of the resin discharged from the die is 2
It was 70 ° C.

Table 1 shows the temperature distribution in the width direction of the resin discharged from the die and the thickness unevenness of the obtained film. The film has a small temperature distribution in the width direction and a relatively small thickness unevenness. It was

[0033]

[Table 1]

[0034]

According to the present invention, the temperature distribution in the width direction of the die can be made extremely small.

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Claims (6)

[Claims] 1. A die for molding a thermoplastic resin into a sheet or film, wherein at least 1 is formed in the width direction of the die.
A mouthpiece for a thermoplastic resin film, wherein a heat pipe of a book is inserted. 2. The base for a thermoplastic resin film according to claim 1, wherein the working fluid of the heat pipe is substantially water. 3. The heating temperature of the die is 200 ° C. or higher, 350
The die for a thermoplastic resin film according to claim 1, which is used at a temperature of less than ° C. 4. The base for a thermoplastic resin film according to claim 1, 2 or 3, wherein the base has a resin cooling mechanism. 5. A method for producing a thermoplastic resin film using the die according to claim 1, 2, 3 or 4. 6. A thermoplastic resin is heated and melted in an extruder to a temperature equal to or higher than the melting point, and then cooled to a temperature range below the melting point and equal to or higher than a crystallization start temperature using the die according to claim 4, and then discharged from the die. A method for producing a thermoplastic resin film produced by the method.