JPS60245539A - Manufacture of polycarbonate film - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of an elongated polycarbonate film having more than 2kg/cm<2> of contraction stress by melting and kneading polycarbonate resins, extruding them through flat die slits and taking up and elongating through cooling rolls. CONSTITUTION:After normally drying and dehydrating material polycarbonate, it is melted and kneaded by an extrusion molding machine and then is extruded into a film through flat die slits after being filtered. The polycarbonate extruded into a film is conducted to cooling rolls through a properly provided air gap and taken up and elongated through rolls. As taking-up and elongation conditions, various molding conditions and physical properties such as type and melting viscosity of material polycarbonate resin may be studied for determination. Whatever determining factors may be, the material polycarbonate should be taken up and elongated so that the contraction stress of elongated polycarbonate film obtained may be more than 2kg/cm<2>. Therefore, it is recommended that the contraction stress be pref. more than 5kg/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing oriented polycarbonate films by melt extrusion.

Traditionally, polycarbonate films have excellent mechanical properties such as high impact strength, as well as electrical insulation properties.

Excellent electrical properties such as dielectric properties, -100 to +13
It is used in a variety of applications, taking advantage of its wide operating temperature range of 0°C and its good secondary processability.

Methods for producing this polycarbonate film include (1) a melt extrusion method and (2) a solution casting method using a solvent. However, in the melt extrusion molding method (2), the moldability of polycarbonate is not necessarily sufficient, and it is very difficult to produce a relatively thin film, and the film thickness is about 20 μm. Moreover, only unstretched films are known. Therefore, these films have limitations in their thickness, strength, rigidity, etc., and their applications are limited to specific applications such as use in the food packaging field.

On the other hand, a new field that focuses on the excellent properties of polycarbonate is separation, which is used as membranes for osmotic devices that selectively separate specific substances from gas or liquid mixtures, and as membranes for reverse osmosis devices that desalinate salt water. There is a membrane. Furthermore, there are other fields such as films for electrical components such as electrical insulation films and capacitor films.

However, for separation membranes, the permeability of gases and liquids is inversely proportional to the membrane thickness, and even for electrical components, membrane thickness is inversely proportional to the miniaturization of parts and the increase in capacitor capacity. It is desired to make the wall thinner. Therefore, in these fields, ultra-thin films with a thickness of 5 μm or less are usually required, and these films are formed by the solution casting method described in (2). However, since a large amount of solvent is used in the solution casting method, recovery and utilization of the solvent is complicated and the molding process is also complicated. Furthermore, there are major drawbacks such as increased manufacturing costs and poor safety and molding work environment.

In addition, the polycarbonate raw material used in the solution casting method must have a high melt viscosity of 40,000 or more, preferably 60,000 or more in terms of viscosity average molecular weight (devitrification may occur unless it is a high molecular weight material that is substantially difficult to melt extrude). It is not possible to obtain a high-quality film.Therefore, due to such high viscosity, it is difficult to manufacture the raw material resin, and expensive special grades must be used. The problem is that it has to be very low, less than 5%, usually 1%, resulting in poor efficiency and a very expensive film, making it difficult to put it into practical use despite its excellent properties. The current situation is that this has not been done.

Under these current circumstances, making polycarbonate films extremely thin is an unavoidable issue in expanding the uses of polycarbonate films. However, no matter how good the mechanical properties of polycarbonate are, as the film is made extremely thin, its strength and rigidity are not necessarily sufficient, and improvements in these properties are desired. One possible method for this purpose is to stretch the film, but since polycarbonate film has very poor stretchability, it is difficult to make it extremely thin by stretching. In order to improve this stretchability, it has been proposed to blend linear polyesters or to closely laminate linear polyester films and then simultaneously stretch the polyesters while controlling their crystallinity. However, this method also has problems in that there is a limit to thinning the film, the quality of the film is not sufficient, and the manufacturing process is complicated.

The purpose of the present invention is to provide a manufacturing method for manufacturing a conventional stretched polycarbonate film, especially an ultra-thin stretched film, by the most common melt-kneading extrusion method, without using a special and expensive forming method called solution casting. It is something to do.

That is, the present invention is characterized in that a polycarbonate resin is melt-kneaded, extruded through a flat die slit, and taken up and stretched through a cooling roll.
The present invention relates to a method for producing a stretched polycarbonate film having a film thickness of 100 g/c+n'' or more.

The present invention will be explained in detail below.

The polycarbonate resin used in the method for producing a polycarbonate film of the present invention is not particularly limited, and any known resin can be used. Representative ones are divalent residues selected from the following general formula group. R represents a monovalent residue selected from the group consisting of a hydrogen atom, a hydrocarbon group, and a halogen atom, and may be the same or different; R. represents a divalent hydrocarbon residue. ] It is a polycarbonate resin represented by These polycarbonate resins have the general formula: (wherein, X and R have the same meanings as above). ], and such bisphenols include, for example, 4,4'-dihydroxy-diphenylmethane, 1,1'-bis(4-
hydroxyphenyl)ethane, 1-1゛-bis(4-hydroxyphenyl)propane, 1,1'-bis(4-hydroxyphenyl)butane, ■・1°-bis(4-hydroxyphenyl)-2-methylpropane , 1,1-bis(4-hydroxyphenyl)hebutane, 1,1°-bis(4-hydroxyphenyl)-1-phenylmethane,
1,1゛-bis(4-hydroxyphenyl)-(4-methylphenyl)-methane.

1,1'-bis(4-hydroxyphenyl)-(4-ethylphenyl)methane, 1,1°-bis(4-hydroxyphenyl)-(4-isopropylphenyl)methane,
1,1-bis(4-hydroxyphenyl)-(4-butylphenyl)methane, 1,1'-bis(4-hydroxyphenyl)-benzyl-methane, 2,2°-bis(4
-hydroxyphenyl)propane, 2,2,-bis(4
-hydroxyphenyl)butane, 2,2°-bis(4-
hydroxyphenyl)pentane, 2°2'-bis(4-
hydroxyphenyl)-4-methylpentane, 2,2゛-bis(4-hydroxyphenyl)hebutane, 2,2.
-bis(4-hydroxyphenyl)octane, 2.2.
-Bis(4-hydroxyphenyl)nonane, 1.1゛-
Bis(4-hydroxyphenyl)-1-phenylethane.

3.3°-11(44, droxyphenyl)pentane,
4,4°-bis(4-hydroxyphenyl)hebutane,
1,1'-bis(4-hydroxyphenyl)cyclopenkune, 1,1'-bis(4-hydroxyphenylfucyclohexane, 2,2'-bis(4-hydroxyphenyl)decahydronaphthalene, 2,2'-bis (4-hydroxy-3-cyclohexylphenyl)propane, 2.2
'=(4,4'-dihydroxy-3-methyl-diphenyl)propane, 2,2'-(4,4°-dihydroxy-
3-isopropyl-diphenyl)butane.

1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, 2,2-bis(4-hydroxy-
3-butylphenyl)propane, 2,2゛-bis(4-
Hydroxy-3-phenyl)propane, 2,2°-bis(4-hydroxy-2=methylphenyl)propane, 1
・l''-bis(4-hydroxy-3-methyl-6-butylphenyl)butane, ■ ・1'-bis(4-hydroxy-3-methyl-6-3-7'tylphenyl)ethane,
1,1゛-bis(4-hydroxy-3-methyl-6-'
M3-butylphenyl)propane, 1,1,-bis(4
-Hydroxy-3-methyl-6=3-7'tylphenyl)butane, 1,1'-bis(4-hydroxy-3-methyl-6-tert-butylphenyl)isobutane, 1,1
'-Bis(4-hydroxy-3-methyl-6=tert-butylphenyl)butane, 1.1'-bis(4-hydroxy-3-methyl-6-tert-butylphenyl)=1-
Phenylmethane, 1,1,-bis(4-hydroxy-3
-Methyl-6=tert-amylphenyl)butane, 4.4
'-dihydroxydiphenyl ether, 4,4-dihydroxy-3,3'-dimethyldiphenyl ether,
4,4'-dihydroxy-3,3-diethyldiphenyl ether, 4,4'-dihydroxy-3,3,-dipropyldiphenyl ether, 4,4'-dihydroxy-
3,3°-diisopropyldiphenyl ether, 4,4
”-dihydroxy-2,2-dimethyldiphenyl ether, 1,1°-dihydroxydiphenyl sulfide,
4,4'-dihydroxy-3,3-dimethyldiphenyl sulfide, 4,4°-dihydroxy-3,3°-diethyldiphenyl sulfide, 4,4'-dihydroxy-2,2,-dimethyldiphenyl sulfide, 4, 4'-dihydroxydiphenyl sulfoxide, 4,4"-dihydroxy-2,2"-dimethyldiphenyl sulfoxide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfone, 4. 4'-dihydroxy-2,2°-dimethyldiphenylsulfone, 4,4'-dihydroxy-3
・3-dimethyldiphenylsulfone, 4,4-dihydroxy-3,3',5,5''-tetramethyldiphenylsulfone, 2,2°-bis(4-hydroxy-3,5
-dichlorophenyl)propane, 2,2゛-bis(4-
Hydroxy-3,5-dibromophenyl)propane, 2
・2°-bis(4-hydroxy-3-chlorophenyl)
Propane, 2,2'-bis(4-hydroxy-3-bromophenyl)propane, 2,2'-bis(4-hydroxy-3-bromo-5-chlorophenyl)propane, 2,
2′-bis(4-hydroxy-3,5-dichlorophenyl)butane, 2,2°-bis(4-hydroxy-3,5
-dibromophenyl)butane, bis(4-hydroxyphenyl)-bis(difluoromonochloromethyl)methane, 1,3-dichloro-1",12,3,.3"-tetrafluoro-2,2'-bis(4 -Hydroxy-3・5-
dichlorodiphenyl)propane, 1,3-dichloro-1
Examples include °·1″·3°·3″-tetrafluoro-2·2″-bis(4-hydroxy-3·5-dibromodiphenyl)propane.

In addition to these, polycarbonate resins made from hydroquinone, resorcinol, 4,4°-dihydroxydiphenyl, etc. can also be used.

these,? Polycarbonate resin length 2.2゛-
Bis(4-hydroxyphenyl) alkanes, especially 2.
Polycarbonate resins made from 2°-bis(4-hydroxyphenyl)propane are preferred.

The molecular weight of the polycarbonate resin used in the present invention is not particularly limited as long as it can be melt-extruded, and generally has a viscosity average molecular weight of 20,000 to 4.
0000 is used.

The raw material polycarbonate resin also includes copolymerized polycarbonate resins such as branched polycarbonate and polyester polycarbonate produced using polyphenols having three or more phenolic hydroxyl groups.

Furthermore, other thermoplastic resins such as polyethylene terephthalate, polybutylene terephthalate, polystyrene, etc. may be added in an amount of usually 50% by weight or less, as long as the object of the present invention is not hindered. Also, if necessary, oxidation stabilizers, heat stabilizers, and light stabilizers.

Various additives such as a fluidity improver, an antiblocking agent and a coloring agent may be added.

In the present invention, raw polycarbonate is usually dried and dehydrated, then melt-kneaded using an extruder such as a -screw extruder, twin-screw extruder, or disc extruder, and extruded into a film through a filter through a flat die slit. Here, examples of the flat die include a T-die and an I-die, and a vent type extrusion molding machine can also be used as the extrusion molding machine.

The polycarbonate extruded into a film is guided to a cooling roll with an appropriate air gap, and then drawn and stretched through the roll. The conditions for take-off stretching may be appropriately determined depending on various molding conditions, the type of raw material polycarbonate resin used, and physical properties such as melt viscosity, but in any case, the shrinkage stress of the stretched polycarbonate film obtained is 2 kg/cs. The film is drawn and stretched so that the shrinkage stress is preferably 5 kg/cm'' or more. Shrinkage stress is the force exerted when a stretched film is heated to try to restore it to the state before stretching (unstretched), and indicates the degree of stretching.

In the production method of the present invention, the melt-kneaded polycarbonate resin is extruded through a flat die slit. In this case, the die lip thickness can be arbitrarily selected in the range of 0.1 to 2fi, preferably 0.2 to 1n+, depending on the molding conditions such as the molecular weight of the raw resin, molding temperature, die lip width, and extrusion rate.

Next, the film extruded from the die lip is guided to a cooling roll, where it is taken up and stretched. The temperature of the cooling roll is usually 50 to 150°C, preferably 70 to 120°C.
Use one that has been heated to . Here, the air gap between the die lip and the cooling roll is usually 20 to 200 mm, preferably 20 to 15 mm, and although it varies depending on the capacity of the extrusion equipment, a relatively small air gap is suitable for the production method of the present invention. There is. Moreover, air can be blown onto the film-like body extruded from the die lip using an air chamber or an air knife, if necessary. In this case, heated air may be used as the air.

The number of cooling rolls may be two or more if necessary, and the take-off speed is preferably such that the draw-down ratio (product film thickness/die lip thickness) is 1/20 or less. Although the film thickness is not particularly limited, it is preferable to stretch the film to a thickness of 20 μm or less, more preferably 10 μm or less, in order to enhance the stretching effect.

The manufacturing method of the present invention continuously integrates melt extrusion film forming and stretching processes, thereby making it possible to stretch polycarbonate films, which were conventionally difficult to stretch.
This makes it possible to produce ultra-thin films of 5 μm or less, which were previously only obtained by solution casting. In addition, the degree of stretching of the film is determined by the drawing ratio, resin temperature, take-up speed, and degree of cooling of the film.

It can also be changed by adjusting the film thickness. In particular, it is believed that the production method of the present invention is made possible by the fact that temperature conditions suitable for stretching can be easily obtained compared to conventional methods of film formation and reheating stretching.

As described in detail above, the present invention is an excellent method compared to the conventional two-step method of film formation and stretching using the melt extrusion method, and is superior to the conventional two-step method of film formation and stretching using the conventional melt extrusion method. This makes it possible to produce ultra-thin films of 10 μm or less, especially 5 μm or less, which had previously been difficult to obtain. Moreover, since the obtained film is stretched, its physical properties such as strength and rigidity are greatly improved. Furthermore, since the film can be manufactured in an integrated manner using simple equipment and processes, it has made it possible to significantly reduce costs compared to the conventional solution casting method used to manufacture ultra-thin films.

Therefore, the stretched polycarbonate film produced by the melt extrusion stretching method of the present invention can be used more economically in fields such as food packaging, which are the applications of conventional melt extrusion films, and as an electrical insulation film for electric motors and generators. ,
It is possible to expand its use to transformers, and even capacitors as a dielectric film.

Examples of the present invention are shown below, but the present invention is not limited to these Examples.

Examples 1 to 2 2,2'-bis(4-hydroxyphenyl)propanpoIJJ<Nate (viscosity average molecular weight: 28,000) was melt-kneaded at a resin temperature of 310°C using an extrusion molding machine to form a mold with a die lip of 0.4 mm. A stretched polycarbonate film of a predetermined thickness was obtained by extruding from a T-guidance tube under the molding conditions of an air gap of 60° C. and a cooling roll temperature of 90° C. while changing the taking-off conditions. Table 1 shows the shrinkage stress and physical property measurement results of the obtained film.

Comparative Examples 1 to 2 In Example 1, a polycarbonate film having a predetermined thickness was obtained with a die lip thickness of 1 mm and an air gap of 100 mm. Table 1 shows the shrinkage stress and physical property measurement results of the obtained film.

Claims (1)

[Claims] ■) A method for producing a stretched polycarbonate film with a shrinkage stress of 2 kg/cm" or more, which comprises melting and kneading a polycarbonate resin, extruding it through a flat die lift, taking it through a cooling roll, and stretching it. 2) Polycarbonate resin has a viscosity average molecular weight of 2000
0 to 40,000. The manufacturing method according to claim 1.