JPS61219622A - Molding of thermoplastic polymer sheet - Google Patents

Abstract

PURPOSE:To shorten the running distance of a sheet-like extrudate leaving a die and arriving to a cooling drum by a method wherein the positional relationship of a device is set so as to tilt the discharge angle of the molten thermoplastic polymer of the die with respect to the vertical plane. CONSTITUTION:The position of a die and the direction of discharge of molten polymer from the die are titled with respect to the vertical plane. In this case, the die 11 is positioned in the same direction as the running direction of the molten sheet 14 extruded from the die 11 or in the forward position with respect to the perpendicular line passing through the center (0) of a cooling drum 13 (the vertical dotted line) or in the counterclockwise direction to the perpendicular line passing through the center (0) of the cooling drum, and is installed by in clination at the angle between the extrusion direction of the molten polymer extruded from the tip 12 of the die and the perpendicular line or the discharge angle of the die. In this case, the molten polymer sheet extruded from the die takes the form of a nearly straight line in the direction of the whole width, which traverses the slit of the die.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method of forming a sheet-like article made of a thermoplastic polymer. More specifically, it relates to a molding method in which when a molten polymer is extruded through a die slit and cooled and solidified on a rotating cooling drum, air microbubbles are not entangled between the cooling drum and the extruded sheet. It is something.

To form a thermoplastic polymer into a sheet, the molten polymer is extruded through a slit-shaped die, immediately brought into contact with the surface of a rotating cooling drum whose temperature is controlled at a predetermined temperature, and then rapidly solidified and taken off. After cooling and assimilation, the hexapolymer sheet is subsequently stretched and heat set to form a film with the desired properties.

Polyester films, which are a typical example of thermoplastic polymers, have excellent properties such as mechanical properties, heat resistance, thermal dimensional stability, chemical resistance, and weather resistance, and also have good electrical properties.

Utilizing this excellent physical property, electrical insulating materials are required to have heat resistance.

It is widely used in various fields such as magnetic recording media materials. In particular, thin polyester films are used as dielectric materials for capacitors and as base films for magnetic tape. BACKGROUND OF THE INVENTION As electronic devices become smaller and lighter, it is desired to develop dielectric materials and magnetic tape materials made of extremely thin films. There is a need to manufacture thin films and sheets of thermoplastic polymers at low cost, but in order to significantly improve productivity, it is necessary to increase the manufacturing speed and reduce the The width is increased over the entire process from forming an unstretched sheet to stretching nine rolls, and furthermore, the width is increased and the manufacturing speed is increased at the same time.

When trying to improve the production speed, the following problems arise in the process of cooling and solidifying a molten thermoplastic polymer sheet on a cooling drum to form it.

■ Excellent adhesion between the molten polymer sheet and the cooling drum reduces the chance of condensation and provides a uniform width.

By obtaining a transparent sheet, the range of conditions that can be achieved becomes extremely narrow.

■ Neck-in narrows the width of the molded sheet, reducing yield in the width direction.

■ The surface of the rotating cooling drum becomes contaminated with low molecular weight substances (oligomers, etc.), resulting in uneven adhesion and making it difficult to obtain a uniform transparent sheet.

■ The f& line of the molten sheet vibrates due to the accompanying airflow generated on the surface of the rotating cooling drum, resulting in uneven thickness.

This results in uneven width.

■ Immediately before the molten polymer sheet extruded from the die slit contacts the surface of the rotating cooling drum, 4? The edges of the molten polymer sheet curl up, making it difficult to form a uniform sheet across the entire width.

These four points tend to become apparent when trying to widen the sheet and increase the production speed, and are a constraint on improving production efficiency.

Prior Art Various attempts have been made to improve the drawbacks of the prior art. Techniques for improving the adhesion between the molten polymer sheet and the rotating cooling drum include (a) pressing the molten sheet against the cooling drum surface using air or gas flow, or creating adhesion by suctioning air (Tokuko Kokō 4);
No. 0-17907, Special Publication No. 13626/1973), 16 Electrostatic adhesion method (fP Publication No. 37-6142/M)
, C. A method of applying a liquid to the surface of a rotating cooling drum (Japanese Patent Application Laid-Open No. 52-65564), 2. A method of pressing a molten sheet with an auxiliary roll (Japanese Patent Publication No. 48-23546), and these techniques. There is a method that combines the two.

However, when attempting to increase the speed for the purpose of improving manufacturing efficiency, the above-mentioned problems remain unresolved with any of the means.

For example, in the case of pressure or suction by an air or gas stream, it is extremely difficult to suppress the membrane vibration of the molten polymer sheet, and the surface velocity of the cooling body can only be increased to about 30 m/min at most. , at speeds higher than this, the sheet height becomes extremely unrestricted. Furthermore, since the sheet is not tightly adhered to the surface of the cooling body, the surface of the cooling body becomes contaminated with low molecular weight substances in a very short period of time, making it impossible to obtain a uniform and transparent sheet.

Furthermore, by electrostatic adhesion method of molten 1liI11 polymer,
When the surface speed of the cooling body exceeds approximately 40 m/ws, air is irregularly drawn in between the surface of the cooling body and the unstretched sheet, the adhesion effect is drastically reduced, the sheet becomes uneven, and the smooth film becomes uneven. I can't get it.

Furthermore, the adhesion method using static electricity has the problem that it is difficult to form a relatively thin unstretched polyester film to a uniform thickness. The reason for this is that the film forming method using electrostatic charges causes dielectric breakdown when the polyester is in a state just before being cooled and solidified from a molten state because the dielectric withstand voltage is significantly lowered. In addition, in order to increase the rate of beef tallow, it is necessary to increase the electrode voltage (by increasing the density of charges deposited on the sheet that is just before cooling and solidifying), but when high voltage is applied, the polyester that is just before assimilation is This causes dielectric breakdown, making continuous molding difficult.Also, even when dielectric breakdown does not occur, the surface of the unstretched sheet tends to be damaged by discharge, and the surface of the stretched film has crater-like formations. A number of defects occur, resulting in a significant decrease in the dielectric strength voltage of the film.

Thus, the thinner the film sheet or the higher the moving speed of the cooling body surface, the more difficult it becomes to form the polymer sheet. As described above, there are still unresolved problems in producing thin films with high efficiency and pressure using electrostatic adhesion methods. JP-A No. 49-99160 proposes applying alcohol having a boiling point of 150 to 220° C. and a surface tension of 50 dynes/an or less to the surface of a rotating cooling drum, and JP-A No. 50-59457 suggests It has been proposed to apply another organic liquid to the surface of the cooling drum. Furthermore, the 1970s
- Publication No. 76173 proposes applying an oily substance to the surface of the cooling drum, but it is difficult to completely remove high boiling point alcohols and oily substances from multiple surfaces of the film in the process after film formation. Moreover, during longitudinal stretching using stretching rolls, high-boiling organic liquids and oily substances accumulate on the surface of the polyurethane, and during transverse stretching, oily substances accumulate inside the tenter. There is a risk of scattering and re-contaminating the film. A dirty surface is not preferable because it brings about disadvantageous results during post-processing of the film, such as coating or vapor deposition of magnetic paints, photosensitive agents, pressure-sensitive adhesives, laminating adhesives, etc.

In order to overcome these problems, a technique has been proposed in which ff1K water is applied to the cooling drum surface. This method has the advantage that the adhesion is uniform and the surface of the cooling drum is not contaminated with low molecular weight substances, but when trying to increase the speed, the neck-in of the molten sheet increases, so the There are disadvantages in that the yield in the direction is low, and the streamlines of the sheet vibrate due to the accompanying air flow generated on the surface of the rotating cooling drum, resulting in non-uniform thickness and non-uniform *.

In any of the conventional techniques described so far, the problem of poor adhesion due to curling up of the edges of the molten polymer sheet, which is the problem of speeding up mentioned above, has not been solved. Techniques that combine two or more of the above-mentioned A, P, C, and 2, such as static air adhesion methods, spraying a gas stream, or pressing with a water-containing fabric. Auxiliary adhesion means to the edge portion have also been proposed.

When trying to increase the speed of these methods, new problems arise such as vibrating the resin film and causing non-uniformity in thickness and width.

Although JP-A-56-53037 proposes a technique using a so-called blade electrode shaped to follow the curved edge of the film, this technique also
% is inconvenient when installed in a narrow space. Furthermore, the shape of the curling up at the edge of the molten resin is not always constant, and its state changes depending on changes in the ambient temperature and the temperature of the molten polymer, which poses practical limitations and hinders its application. There are unresolved issues.

As a result of the structure of the invention, the profile flow of the molten polymer sheet extruded from the die slit becomes substantially VC across the entire width of the sheet, and the molten polymer is extruded from the die slit and cooled. In addition to shortening the length of the space until it contacts the body surface (free J%) of the molten sheet as much as possible, the cooling drum is about 11 times smaller! If the relationship is selected within a certain range and the liquid is applied to the surface of the cooling body, the reduction in sheet width caused by neck-in can be suppressed, even if the liquid is applied to the surface of the cooling body. The present invention K@I was achieved by discovering that it is possible to obtain a homogeneous tC film by preventing air from being entrained between the two.

That is, in the method of the present invention, a molten thermoplastic polymer is extruded into a sheet from a goo, and the sheet-shaped extrudate is brought into contact with the surface of a rotating cooling drum coated with a thin liquid film, and then cooled and solidified. In the method of forming a sheet from a polymer, the die is oriented in the direction of travel of the sheet-like extrudate, the core die is positioned forward of the vertical plane including the rotation axis of the cooling drum, and the molten thermoplastic By setting the positional relationship of the button device so that the discharge angle of the combined product is inclined with respect to the vertical plane, the traveling distance of the sheet-like extrudate from leaving the die to reaching the cooling drum is shortened. This is a method for molding a thermoplastic polymer sheet.

Here, the advancing direction of the sheet-like extrudate means the conveyance direction of the extruded sheet-like extrudate immediately after it contacts the cooling drum. The position in front of the vertical plane passing through the rotation axis (center) of the cooling drum is the position where the straight line connecting the tip of the die and the center of the cooling drum is inclined to the perpendicular line passing through the center of the cooling drum, as shown in Figure 1. It means to position it like this. The inclination angle α in FIG. 1 is preferably set within 45°.

In addition, the discharge angle of the die means the angle formed by the extrusion direction of the molten polymer extruded from the extrusion die and the perpendicular line passing through the center of the cooling drum, and the discharge angle β in the fa1 diagram is 45° to 85°.
A range of 50° is preferred.

The sheet forming method of the present invention will be further explained with reference to the drawings. FIG. 5 is a side view showing a conventional sheet forming method. The sheet 14 of molten 7111 extruded from the die 11 comes into contact with the surface of the rotating cooling drum 13. The molten polymer sheet is applied to the surface of the cooling drum using a coating machine 21.
The dripping film 22 applied by
The surface density is 5m￥l, and it is collected after being cooled and solidified.
15 and sent to the next process. In the conventional technology, the positional relationship between the cooling drum and the die is as shown in FIG.
The direction of the die is arranged so that the tip 12 of the die is directly above the rotation axis o of the cooling drum and is on a perpendicular line connecting the die and the rotation axis.

On the other hand, in the present invention, the position of the die and #1. −
The direction in which the polymer is discharged is inclined as shown in the first factor or in FIG.

At this time, the die 11 is positioned in the same direction K as the traveling direction of the extruded R-fused sheet 14, and in front of the perpendicular line passing through the center 0 of the cooling drum 13 (point # indicating the vertical direction), that is, in the drawing direction. A vertical line aF passing through the center 0 of the cooling drum 13 [located in a counterclockwise direction with respect to the angle formed by the perpendicular line and the extrusion direction of the molten polymer extruded from the tip 12 of the die, that is, the angle corresponding to the discharge angle Install it at an angle. At this time, the molten polymer sheet extruded from the die becomes very close to a straight line in the entire width direction that cuts through the slit of the die. This situation is shown in Figure 3. The side view in FIG. 4 shows the shape of the streamlines at the edge of the sheet and the portion away from the edge just before the molten polymer extruded from the die comes into close contact with the cooling drum in the prior art.

The edge portion of the sheet means an area ranging from 30 meters to 50 meters measured from the longitudinal end of the die slit.

In this way, in the conventional technology, the line of contact when the sheet comes into close contact with the cooling drum in the width direction is bent, so the edge part lands on the cooling drum later than the other parts, and the edge part lands on the cooling drum later than the other parts. The force applied to the M-sheet becomes unbalanced, causing vibration of the sheet and swaying the line of contact across its width, making the thickness of the sheet unrestricted.

This sheet vibration tends to increase as production speed increases. On the other hand, in the method of the present invention (as shown in Figures 2 and 3), by tilting the discharge angle, the sheet extruded from the die extends over the entire width and becomes extremely close to the line 1. Because it contacts the cooling drum uniformly, vibrations in the space of the sheet can be prevented.As a result, a uniform sheet with less uneven thickness can be obtained.

According to the method of the present invention, since the molten polymer sheet adheres closely,
To produce a film with high efficiency that has extremely uniform thickness and transparency and has no surface defects due to air entrainment.

In order to carry out the method of the present invention more effectively, the die 11 is positioned 00 to 45 degrees forward with respect to the perpendicular passing through the center of the cooling drum, and the discharge angle of the die is set to 45 degrees to 85 degrees. is preferred. Further, it is preferable that the die tip and the surface of the cooling drum be as close as possible.

The optimal setting values for the angle α and the discharge angle β, which are perpendicular to the straight line connecting the die tip and the center 0 of the cooling drum, vary depending on the thickness of the molten sheet, the viscosity, the surface speed of the cooling drum, etc., and can be adjusted as appropriate depending on the purpose. If the angle α that can be determined is 00 or less (in the direction opposite to the direction in which the molten sheet travels), or if the discharge angle β is 45
If the temperature is less than 1, the effect of adhering the molten T-sheet to the cooling drum and the effect of preventing membrane vibration caused by the rising edges will be reduced.

In addition, if the angle α is 45° or more, the molten polymer sheet discharged from the die will not be fully adhered to the surface of the cooling drum, and will not be sufficiently cooled and solidified, causing it to slip on the surface of the cooling drum. It causes wrinkles and walnuts, making the sheet uneven.

If the discharge angle β is 85° or more, the traveling distance (interval) from the die lip tip to the point where the molten sheet lands becomes too long, and the film in the space is likely to be captured, resulting in non-uniformity of the sheet.

As is clear from the above-mentioned details, the method of the present invention sets the extrusion die and the discharge square box to new positions and angles. This makes it possible to produce an excellent thermoplastic polymer sheet with no surface defects due to inclusions.

The thermoplastic polymer to which the present invention can be applied is preferably one that does not absorb a large amount of water when water is used as a liquid film. Examples of such polymers include polyesters and polycarbonates as described below. This polyester and 17
So, polyethylene terephthalate, polytrimethene terephthalate, polytetramethylene terephthalate,
Polypentamethylene terephthalate, polyhexamethylene terephthalate, polyethylene 26 naphthalate, polytetramethylene-2,6-naphthalate, polyhexamethylene-2,6-naphthalate, polytrimethylene-
2,6-naphthalate, polypentamethylene-2,6-
naphthalene), 4,4-dihydroxydiphenyl-2,
2-propane polycarbonate and the like are preferably used. The thermoplastic polyester may be a copolymer or a blend of two or more thermoplastic polyesters.

Book 9 QFIK The cooling drum used in this article is one that has a surface made of materials such as metal, plastic, or rubber, and is forcibly cooled by a circulating refrigerant made of liquid or gas. This is a book that will be published. The liquid applied to the cooling drum used in the present invention is preferably water, methyl alcohol, ethyl alcohol, acetone, or the like.

When water is used, it is sufficient to use water that is generally used in water supplies, and if necessary, a small amount of surfactant may be added. Additionally, water can be used as a mixed solution with methyl alcohol, ethyl alcohol, or acetone. Thus, the liquid applied in the present invention is substantially inert to the thermoplastic polymer sheet, and the fll+! Preferably, it can be simply removed from the surface of the film sheet.

The present invention will be explained in detail below using specific examples.

Example, Comparative Example 1 Polyethylene terephthalate having a # of 0.64 (measured as 0-chlorophene/-luya solvent at 25°C) was heated to 290°C in a press! P-Fusakaki 1 Castle 1000+
A cooling drum with a surface temperature of 25°C (diameter 1
500 m) - extruded and cooled to solidify. Is there water on the surface of the cooling drum? 't III 5 pmwo1=-
It was applied using a coater.

Cooling Dom 1! ? ] Phase inversion C preparation: The conventional molding equipment installed directly above (discharge angle O0), and the extrusion die angle α and discharge angle β are set to α = 0° and β = 60°, respectively.
Using the set molding equipment of the method of the present invention - Figure 42 (7), the surface speed of the cooling drum was changed for each, and the discharge size of the polyester was adjusted to 200. um
While keeping the thickness constant by 1♀, pound the surface of the cooling drum rapidly for 4
From Q gl/m, the speed was increased by 1 every 10 m/decoration. The moldability of the U7 sheet was evaluated by observing the transparency, uniformity of thickness, air entrainment, etc. of the obtained sheet.

The polyester sheet printed by the method of the present invention has an extremely uniform thickness, has excellent smoothness, and even when the cooling drum surface speed is increased to 90 m/m, the surface is free from membrane vibration and air entrainment. No defects occurred. On the other hand, the surface speed of the cooling drum for the conventional polymer sheet was 60
When exceeding m/am, membrane vibration began to occur. Also, the width of the seat is slightly reduced due to the neck-in.

[Brief explanation of the drawing]

t41 to 3 are side views showing an embodiment of the method of the present invention, and FIGS. 4 and 5 are side views illustrating the conventional method. In the drawings, 11 is a die, 12 is a grip, 14 is a molten polymer sheet, 13 is a cooling drum, and 22 is a liquid film applied to the drum surface.

Claims (2)

[Claims] (1) From a thermoplastic polymer obtained by extruding a molten thermoplastic polymer into a sheet from a die, bringing the sheet extrudate into contact with the surface of a rotating cooling drum coated with a thin liquid film, and cooling and solidifying. In a method for forming a sheet, a die is positioned in front of a vertical plane including the rotation axis of a cooling drum, and the extrusion angle of the molten thermoplastic polymer from the die is inclined with respect to the vertical plane to extrude the molten thermoplastic polymer into a sheet. A method for forming a thermoplastic polymer sheet, characterized by shortening the running distance of an object from the die to the surface of the cooling drum. (2) The method for molding a thermoplastic polymer sheet according to claim 1, wherein the thermoplastic polymer is a linear aromatic polyester.