JPS5933096B2 - Method for manufacturing thermoplastic resin sheet or film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously and stably producing a thermoplastic resin sheet or film with little thickness unevenness.

Conventionally, in the process of melting and extruding thermoplastic resin through a die to form a sheet or film, and rapidly cooling and solidifying it on a casting drum, an air knife was installed opposite the casting drum to supplement the cooling capacity of the casting drum. However, a method is generally known in which air is blown onto the sheet or film on the casting drum to assist in cooling the sheet or film.

It is also known that one of the causes of film thickness unevenness is already inherent in the cooling process. 5 The present inventor has conducted extensive research into a method for manufacturing sheets or films of molten thermoplastic resin with less uneven thickness and excellent transparency by improving the cooling process when manufacturing sheets or films of molten thermoplastic resin. As a result, this requirement is satisfied by detecting the temperature of a specific surface of the film 10 at a specific position in the process and controlling the air blowing conditions from the air knife so that the temperature of the specific surface falls within a predetermined temperature range. The inventors have discovered that it is possible to continuously and stably produce sheets or films produced by the above methods, and have arrived at the present invention.

That is, the present invention continuously molds a thermoplastic resin melted and extruded from a die onto a casting drum, and rapidly cools it using the drum and air knife to produce a sheet or film. The surface temperature of the air knife air blowing surface of the sheet or film is detected at the position where the film leaves the casting drum surface, and the air knife is applied from the surface facing the casting drum so that the detected temperature falls within a predetermined temperature range. Air blowing strip 2
This is a method for producing a thermoplastic resin sheet or film, which is characterized by controlling five factors.

The manufacturing method of the present invention will be explained in more detail.

First, when manufacturing a sheet or film made of thermoplastic resin, the present inventors have discovered that when manufacturing a sheet or film made of thermoplastic resin, the surface of the sheet or film that is not in contact with the casting drum at the position where the sheet or film leaves the casting drum (hereinafter referred to as There is a close relationship between the temperature (hereinafter abbreviated as T temperature) of the sheet or film (hereinafter abbreviated as T temperature) and the physical properties, especially the thickness unevenness and transparency, etc. of the sheet or film. By controlling the physical properties of the sheet or film,
We determined that quality could be controlled, and the temperature was controlled by detecting the temperature of side A at the separation position and keeping the temperature within a predetermined temperature range (usually from a temperature higher than the predetermined temperature to a lower temperature). ), the wind velocity of the air from the air knife (usually located on the opposite side of the cast drum center line from the disengagement position - the side where side A is hotter) relative to side A. , adjust air volume, spray angle, etc.
The present invention is achieved through control. As mentioned above, there is a known method for supplementing the cooling capacity of the casting drum by blowing air against side A using an air knife, but the degree and conditions of this air blowing may be determined based on the temperature of side A at the separation position. The method of further improving thickness unevenness and transparency through adjustment is a completely new method. The thermoplastic resin used in the present invention is usually preferably a crystalline polymer, such as polyethylene, polypropylene, polystyrene, polyvinylidene chloride, nylon 6, nylon 66, polyethylene terephthalate, polyethylene-2,6-naphthalate, Examples include polybutylene terephthalate, polybutylene-2,6-naphthalate, and polyesters, particularly polyethylene terephthalate, are preferred.

The term "sheet or film" in the present invention refers to a sheet-like material or a film-like material whose thickness is not particularly limited, but is preferably 0.5 to 5177 mm thick! , particularly preferably 1-3T
This is the thickness of I&IL.

In the present invention, the position where the sheet or film leaves the casting drum means that the surface of the sheet or film that has been cooled by direct contact with the casting drum (the surface opposite to the A side) is in contact with the casting drum. Strictly speaking, it refers to the position where direct contact ends, but in the present invention, it is approximately 10 degrees below that position. , preferably within 3 crn, the T temperature detection position on the A side may be slightly shifted along the longitudinal direction of the sheet or film in the traveling direction or preferably in the opposite direction.

The T temperature may be detected using either a contact or non-contact thermometer, but it is preferable to use a non-contact thermometer (for example, an infrared thermometer), which has no adverse effect on the quality of the sheet or film. It is preferable to use The air knife used in the present invention is not particularly limited as long as it can blow air toward the A side of the sheet or film and has the ability to assist in cooling the casting drum.

In order to control the blowing conditions of air blown to side A,
At least one condition that affects the cooling efficiency of the sheet or film, such as the wind speed, air volume, temperature, or blowing angle of the blown air, is changed. Among these conditions, changing the wind speed is a preferable condition for increasing cooling efficiency. Methods for controlling the air speed include, for example, changing the width of the blowout loss slit of the air knife, changing the air flow rate of the proar that sends air to the air knife (for example, changing the opening degree of the shutter between the air knife and the proar, and the number of rotations of the proar). There are methods such as changing the distance between the air knife and the sheet or film, etc.), or changing the distance between the air knife and the sheet or film.
In order to change conditions while maintaining stable quality, it is advantageous to change the amount of air blown from the prower to the air knife.

The blowing position of the air knife may be any position as long as the sheet or film is in close contact with the casting drum, but it is preferable that the A-side temperature of the sheet or film on the casting drum (the sheet at the die exit It is preferable that air be blown from at least the first stage air knife to a point where the temperature is higher than (film temperature+T temperature)/2. In the present invention, only one air knife may be installed or two or more air knives may be used.

However, the feature of the present invention is that the T temperature is measured and the air blowing conditions from the air knife are controlled based on this.
This can be easily accomplished by using one air knife. Wind speed control can be reliably carried out by measuring the wind speed at the surface where the blown air exits the outlet of the air knife or at the point where the air contacts the sheet or film. The wind speed can be measured by installing an anemometer such as a hot-wire anemometer near the air knife outlet or the A side of the sheet or film, or by measuring the internal pressure of the air knife and determining the relationship between the internal pressure and the blowing wind speed determined in advance. For example, an indirect method using a calibration curve showing T of side A at detachment position
This is the A-side temperature at which the thickness unevenness and transparency of the sheet or film produced are significantly improved by keeping the temperature within a certain range, and this temperature depends on the type of thermoplastic resin that is the sheet or film material. It is not uniform.

For example, if the thermoplastic resin is polyethylene terephthalate, it will be 90 to 120℃, and if the thermoplastic resin is polyethylene terephthalate, it will be 70℃ or 70℃ if the thermoplastic resin is polyethylene terephthalate.
0 to 100°C, and 80 to 1000°C for polyvinyl chloride. To carry out the invention, the T of the sheet or film is
Although it is possible to create a system that detects the temperature and then adjusts the blowing speed of the air knife, for example, it is possible to continuously and automatically measure the internal pressure of the air knife so that the T temperature falls within a predetermined range. For example, this can also be done by a system that automatically changes the shutter opening/closing degree between the blower air knives while checking the internal pressure of the air knives.

In this way, the detection of the surface temperature in the present invention means detecting it each time, or detecting the temperature in advance by taking into consideration the type of thermoplastic resin, the discharge amount, the cooling capacity of the drum or air knife, etc. good. Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the base in the example is a value measured with an integrating sphere type base meter manufactured by Nippon Seimitsu Kogaku, and the thickness unevenness is a value measured with an electronic micrometer manufactured by Anritsu Electric. Example 1 In the drawing shown in FIG. 1, in the step of bringing a polyethylene terephthalate sheet 2 having a thickness of 2 mu that has been melt-extruded from a die 1 into close contact with a casting drum 3 and cooling it, the sheet is removed from an air knife 4. Relative humidity towards 60
%, and forced cooling was performed by blowing air at an air temperature of 20°C.

Since the preferable T temperature range in this example is 90 to 120°C, the damper 6 attached to the air knife air supply duct is opened and closed according to a calibration curve determined in advance so that the T temperature becomes 105°C. 2), the air knife 4
The speed of the air blown towards the sheet is 19 m/
When the internal pressure of the air knife was set to 90 mm in water so as to be Sec, the T temperature was stable at 105 °C as expected, and the variation in the thickness of the obtained sheet was 3% and the base was 8%. . As a result of manufacturing a polyethylene terephthalate sheet while appropriately operating the damper 6 to maintain the internal pressure of the air knife at 90±5 degrees,
The T temperature was maintained at 105±2°C, the thickness unevenness of the sheet was also maintained at about 3%, and the base was maintained at about 8%. On the other hand, when the internal pressure of the air knife 4 was set to 20 mm in water, the air blowing speed from the air knife was 11 m/Sec, and the T temperature of the sheet was 135°C. The thickness unevenness of the obtained sheet reached 10%, and the base thickness reached 12%.

[Brief explanation of the drawing]

FIGS. 1 and 2 are examples showing preferred embodiments of the present invention.

Claims (1)

[Claims] 1. When manufacturing a sheet or film by continuously molding a thermoplastic resin melt-extruded from a die onto a casting drum and quenching it by the drum and air knife, the sheet or film is The surface temperature of the air blowing surface of the sheet or film is detected at the position where the air knife leaves the surface of the casting drum, and the air knife is applied from the surface facing the casting drum so that the detected temperature falls within a predetermined temperature range. 1. A method for producing a thermoplastic resin sheet or film, comprising controlling air blowing conditions. 2. Claim 1, wherein the thermoplastic resin is polyethylene terephthalate and the predetermined temperature is 90 to 120°C.
The method described in section.