JPS6325016A - Manufacture of thermoplastic resin film - Google Patents

Abstract

PURPOSE:To permit high-speed molding, by a method wherein reticulated engraved parts with the mesh and depth of specified ranges are provided on the parts of the specified rate of both widthwise ends of a cooling roll while a doctor knife is provided above the surface of the cooling roll, in order to unify the thickness of liquid coated on a resin film. CONSTITUTION:The roughness of an engraved part should be selected in accordance with a molding speed, the viscosity of liquid or the like, however, the range of 40-250 mesh and the range of the depth of 10-250mu are necessary. The total width of the engraved parts is necessary to be at most 10% of the width of a die and a range within 0.5-10% is preferable. Further, the liquid is coated from the engraved parts 4 and excessive liquid is removed by a doctor knife 5, therefore, the level of the liquid will never become higher than the surface of the cooling roll 3 substantially whereby a phenomenon, in which the liquid is collapsed when it contacts with a molten resin film 2 and is shifted to the center of the roll, may be prevented. The boiling point of the liquid is preferable to be 50 deg.C or higher in a normal pressure and the viscosity of the same is preferable to be 200 centistokes 37.8 deg.C or less.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a thermoplastic resin film (in the present specification, meat is also included in the category of film), and more specifically relates to a method for producing a thermoplastic resin film (in this specification, meat is also included in the category of film). When producing the extruded thermoplastic film from the die onto the cooling roll surface,
Improving the adhesion between the film and the moving cooling roll,
The present invention relates to a method for producing thermoplastic resin films with extremely excellent surface quality at high speed.

[Conventional technology]

Generally, thermoplastic resin films are produced by extruding a molten thermoplastic resin through an extrusion die, casting it onto a moving cooling roll that is forcibly cooled, and solidifying it by cooling.
It is then manufactured by peeling off the roll.

However, such a method is prone to various troubles, and it has been virtually impossible to obtain a resin film having the desired quality.

That is, firstly, the thermoplastic resin in the molten state tends to slip on the entrance surface of the moving cooling roll, causing wrinkles and sagging on the surface of the cooled and solidified resin film, and secondly, even when such slipping does not occur, Due to rapid cooling on the surface of the moving cooling roll, the film width tends to decrease and a resin film with irregular width is likely to be produced. Thirdly, due to the irregular entrainment of air between the molten thermoplastic resin and the moving cooling roll, The resin film tends to have unevenness and cooling unevenness.Fourth, the position where the molten thermoplastic resin contacts the moving cooling roll is unstable and changes irregularly, so the resin film tends to have uneven thickness and cooling spots. There were other defects. In addition, these phenomena have become more pronounced as the moving speed of the moving cooling roll increases as the production volume increases.

All of these defects are thought to be caused by insufficient adhesion between the molten thermoplastic resin and the moving cooling roll, and various attempts have been made to improve this adhesion.

First, a method is known in which the optical surface of the extruded molten thermoplastic resin is mechanically pressed by blowing air or by using a pressure drum. However, the former method has the disadvantage that the surface properties of the resin film are limited due to turbulence in airflow, fluctuations in fluid pressure, etc.

Second, the surface on the molten thermoplastic resin side or the opposite surface,
Alternatively, electrostatic charges are deposited on the surface of the moving cooling roll coated with insulation, and at the same time the moving cooling roll is grounded, and an electric attraction is generated between the molten thermoplastic resin and the moving cooling roll due to different types of static charges, and the melting heat is generated. A method of bringing a plastic resin into close contact with a moving cooling roll is known (for example, Japanese Patent Publication No. 37-6142, Japanese Patent Publication No. 3535-1982, Japanese Patent Publication No. 14786-1973, Japanese Patent Publication No. 14786-1985).
No., Special Publication No. 1978-14786, Special Publication No. 48-2931
Publication No. 1, etc.).

Although these methods eliminate many of the conventional defects mentioned above, the local concentration of static charge applies a sudden force to the molten thermoplastic resin, causing the resin film to undergo a sudden change in stress. Wrinkles and thickness unevenness tend to occur on the surface, and because the adhesion is so strong, defects on the surface of the moving cooling roll are transferred directly to the resin film.Furthermore, the static charge that remains even after adhesion causes dust to adhere. Furthermore, when the moving speed of the moving cooling roll is increased to increase production, a phenomenon in which the molten thermoplastic resin vibrates between the moving cooling roll and the extrusion die is observed. As a result, new defects such as periodic fluctuations in the width of the resin film and the tendency to generate cooling spots occur, and it is not always possible to obtain a resin film of satisfactory quality.

Thirdly, a method is known in which a liquid is interposed between a molten thermoplastic resin and a moving cooling roll. Of these, the method disclosed in British Patent No. 1,312,519 is a method that eliminates the above-mentioned electrostatic charge. By using a method that uses a static charge in combination, and also applying an ultra-thin layer of thermally conductive liquid on the surface of a moving cooling roll and extruding a thermoplastic resin on top of this, we are able to overcome the excessively strong adhesion that conventional methods using static charges have had. This is intended to eliminate defects such as transfer of surface defects on the moving cooling roll due to the effect.

However, in this method, the thermally conductive liquid ultra-thin film on the moving cooling roll cools down by evaporation and absorption of thermoplastic resin by the time the moving cooling roll is reused (when the cooling roll makes one rotation). However, since this amount of consumption is generally extremely small, the coating thickness must be extremely thin. The thickness of this film varies depending on the type of thermoplastic resin to be used, the temperature of the moving cooling roll, etc., but it is generally several 1
It is required to be 0μ or less, and in particular, in the case of polyethylene terephthalate, it is required to be in the range of 0.5 to 10μ. However, it is generally extremely difficult to provide such a thin coating on the surface of a moving cooling roll, and it is especially difficult to control the coating thickness to the optimum thickness for the target thermoplastic resin or to respond to changes in manufacturing conditions. Since it is nearly impossible to control the film thickness by using such a method, it has been practically difficult to obtain a thermoplastic resin film having the desired quality by such a method.

Furthermore, as a method that is believed to be based on a similar concept, a method disclosed in Japanese Patent Application Laid-open No. 49-99160 is known. In this method, alcohols with a boiling point of 150 to 220°C and a surface tension of 50 dyne/crn or less at room temperature are applied to the surface of a moving cooling roll, and a molten linear polyester resin is extruded onto the surface of this roll and cooled. It is intended to be molded.

However, since the alcohols used in this method have a boiling point of 150 to 220°C and are difficult to evaporate, consumption of alcohols by evaporation is small, and as a result, the method disclosed in British Patent No. 1,312,519 mentioned above Similar to the method described above, it is necessary to make the coating thickness extremely thin, and in reality, this method has the drawback of being extremely difficult to implement.

[Problem that the invention seeks to solve]

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, prevent unstable shrinkage and flow at both ends of a molten resin film, securely fix both ends of the film on a cooling roll, and improve the adhesion between the two. A method for producing a thermoplastic resin film that improves the temperature, suppresses air entrainment between the molten resin film and the cooling roll, eliminates uneven thickness and wrinkles in the film, and solves the problems of low gloss and low transparency. Our goal is to provide the following.

Another object of the present invention is to provide a method for producing a thermoplastic resin film that solves the conventional problems particularly during high-speed molding and thin film molding.

[Means for solving problems]

The above objects of the present invention are as follows: 1. In a method of manufacturing a film by extruding a molten thermoplastic resin from a die onto the surface of a cooling roll, the cooling roll has a mesh of 40 to 250 mesh at a depth corresponding to both ends of the film width. It has a net-like engraved part with a diameter of 10 to 250 microns, and the total width of the engraved part is at most 10 inches of the die width, and furthermore, a liquid is supplied to the engraved part from a liquid application device. This is achieved by a method for producing a thermoplastic resin film characterized by the following.

Further, the above-mentioned object of the present invention is achieved by a method for producing a thermoplastic resin film, characterized in that after supplying liquid to the engravings formed on the cooling roll, excess liquid is removed using a doctor knife.

As the thermoplastic resin used in the present invention, any publicly known thermoplastic resin can be used, such as polyolefin resins such as polyethylene and polypropylene, polyester resins such as -lyethylene terephthalate and polybutylene terephthalate, polyhexamethylene adipamide, Poly-ε
- Capramide, poly-11-aminoundecamide and their copolymers, blends of polyamide resins, polystyrene resins, acrylic resins such as polymethyl methacrylate, polyacetals, polycarbonates, polyenylene oxynide, polyethylene arylate, polysulfone,
polyether sulfone, polyphenylene sulfide,
Examples include polyimide, polyamideimide, polyimide such as etherimide, and polyetherketone.

The thermoplastic resin is extruded from a die onto the surface of a cooling roll, and in the present invention, the cooling roll must have a mesh-like engraved portion at portions corresponding to both ends of the film width. To explain this with reference to Figure 1, in the figure, l is a T-die, 2 is a molten thermoplastic resin film, and 3 is a cooling roll. For example, a net-like engraving portion 4 similar to that of a gravure roll is provided. A liquid such as water is uniformly supplied to this engraving portion from a liquid applicator. In this way, the adhesion between both ends of the film and the cooling roll is improved, and uneven air entrainment between the molten film and the cooling roll can be prevented.

Furthermore, in order to prevent the liquid applied to the engraved part of the cooling roll from migrating to the center of the roll, for example, in the case of a gravure roll, a doctor knife is used as shown in Figure 2 (0) (b).
It is necessary to provide a cooling roll on the surface of the cooling roll, to make the applied liquid uniform, and to remove excess liquid so that the height of the applied liquid is not higher than the roll surface.

Incidentally, a method of applying a liquid to a cooling roll to increase the adhesion with the molten film is disclosed in Japanese Patent Application Laid-Open Nos. 49-9916 and 55-44804. In addition to the problem of liquid removal, the liquid tends to be crushed between the rolls of film and gradually migrate to the center of the rolls, resulting in uneven cooling.These problems are solved by the present invention.

The liquid used in the present invention has a boiling point of 50°C (normal temperature) or higher,
Preferably, the viscosity is 200 centistokes (37.8° C.) or less. If the boiling point of the liquid is less than 50° C., it is highly volatile and not only is it impossible to obtain sufficient effects, but also there is a problem that depending on the liquid used, it may pollute the environment.

Also, if the viscosity is higher than 200 centistokes,
This is undesirable since it creates a large resistance when the film is peeled off from the chill roll. Such a liquid is
Examples include water, acetone, ethanol, mineral oil, vegetable oil, etc.

The engravings made on the cooling roll are not affected by the shape of the mesh. For example, a circle, ellipse, square, hexagon, etc. can be adopted depending on the film thickness, molding speed, and liquid used. The roughness of the engraving should be selected depending on the molding speed, viscosity of the liquid, etc., but it should be 40 to 250 mesh, 10 to 25
A range of 0 microns is required. If the amount is outside this range, the amount of liquid applied will be too much or too little, and the effects of the present invention will not be obtained. The total width of the engraving part is at most 1 of the die width.
0 inches is required, and the range of 0.5 to 10 inches is preferable.

If the total width of the engraved portion exceeds 10%, it is unfavorable from the viewpoint of productivity, as the effective width of the film becomes narrow. Further, the width of the engraved portion may be the same or different at both ends of the film width.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Foripropylene (kfFlo) was extruded at a resin temperature of 250°C using a T-die extrusion device (extruder 65mm diameter, die width 1000m,
on the cooling roll surface (with a lip spacing of 0.5 vm)
20°C).

The cooling roll used was a 300φ mirror-finished roll surface with 60 meshes and 20 net-like engravings of 170μ in depth on each side of the film width, and a doctor was used on the engravings. I put a knife on it.

Water at 20℃ [boiling point 100
°C, viscosity approximately 0.660 centistokes (37.8 °C)
] at a take-up speed of 75 m/it+in to a thickness of 20 mm.
A film of μ was obtained.

Example 2 The mesh of the mesh engraving part was 100. A film with a thickness of 20 μm was molded in the same manner as in Example 1 except that the depth was 100 μm.

Example 3 The mesh of the mesh-like engravings was 100 mm, the depth was 100 μm, and the liquid was composed of a fraction with a boiling point of 350° C. or higher. A film having a thickness of 20 μm was formed in the same manner as in Example 1, except that mineral oil (saturated hydrocarbon) having a viscosity of about 32 centistokes (37.8° C.) was used.

Comparative Example 1 A 300φ mirror finish roll without engravings was used as the cooling roll, and a doctor knife was not used (water was supplied to the same position as in Example 1).
A film was molded in the same manner as in Example 1 to obtain a film with a thickness of 20 μm.

Comparative Example 2 A film was molded in the same manner as Comparative Example 1 except that water was not supplied to the engraved portion, and a film with a thickness of 20 μm was obtained.

Comparative Example 3 A film with a thickness of 20 μm was molded in the same manner as in Example 1, except that a doctor knife was not used.

Comparative Example 4 A film with a thickness of 20 μm was molded in the same manner as in Example 1, except that the mesh-like engraving portion was 30 meshes and the depth was 300 μm.

Comparative Example 5 A film with a thickness of 20 μm was molded in the same manner as in Example 1, except that the mesh-shaped engraving portion was 300 meshes and the depth was 5 μm.

Table 1 shows the properties of the films obtained in Examples 1 to 3 and Comparative Examples 1 to 5.

Table 1 Adhesion between the medium molten film and the cooling roll [Effects of the invention] According to the present invention, in the process in which the molten resin film extruded from the die contacts the cooling roll and is cooled, the molten resin film is uniformly applied to the cooling roll. Furthermore, since the liquid is applied from the engraved area, excess liquid can be easily removed using a doctor knife. Therefore, the liquid level is never higher than the cooling roll surface, and the melting This can prevent the liquid from being crushed and transferred to the center of the roll when the resin film comes into contact with the liquid. As a result, even during high-speed molding or thin film molding, the entrainment of air between the molten resin film and the cooling roll can be sufficiently suppressed, and the adhesion between the two can be improved. It became possible to obtain a good film without problems such as uneven thickness, wrinkles, low gloss, low transparency, and occurrence of cooling spots.

[Brief explanation of the drawing]

The drawings are schematic diagrams of a typical apparatus for carrying out the method of the present invention; FIG. 1 is a top view, FIG. 2(a) is a side view, and FIG. 2(b) is a perspective view. DESCRIPTION OF SYMBOLS 1... Die, 2... Molten resin film, 3... Cooling roll, 4... Net-like engraving part.

Claims (2)

[Claims] (1) In a method of manufacturing a film by extruding a molten thermoplastic resin from a die onto the surface of a cooling roll, the cooling roll has a 40 to
It has a net-like engraving part of 50 mesh and a depth of 10 to 250 microns, and the total width of the engraving part is at most 10% of the die width, and the engraving part is supplied with liquid from a liquid coating device. A method for producing a thermoplastic resin film characterized by: (2) The method for producing a thermoplastic resin film according to claim (1), characterized in that after supplying liquid to the engravings formed on the cooling roll, excess liquid is removed using a doctor knife. :