JPS6274608A - Manufacture of polyimide film - Google Patents

Abstract

PURPOSE:To eliminate the condensation of liquid with an odor of solvent and consequently reduce the consumption of energy and the cost of facilities by a method wherein a plurality of sheets of film, which is obtained by flowing polyimide solution or polyamide acid solution over a base plate and drying, are simultaneously heat-treated under the state that predetermined intervals are provided between the sheets of the film. CONSTITUTION:At least two sheets of dry film are simultaneously charged in a heat treatment furnace in order to heat-treat the film under the state that both edge parts of the respective sheets of the film are held. At this time, the respective sheet of the film are arranged so as to have a gap of at least 5mm therebetween. The gap is necessary to completely remove the solvent evaporated from the film during heat treatment and the moisture developed together with the imide ring closure reaction from the surfaces of the sheets of the film. If the sheets of the film are in contact with each other, the evaporated gas does not fully escape from the surfaces of the sheets of the film and consequently stagnates in highly concentrated state and unfavorably condenses. The effects due to said condensation can completely be removed by providing the gap of 5mm between the respective sheet of the film.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a polyimide film.

[Conventional technology]

Conventionally, methods for obtaining polyimide heat-resistant films include:
Contains polyimide or polyamic acid, concentration 5-30
% solution by weight onto a metal substrate, such as a stainless steel belt substrate, and drying the solution to form a dry film;
Thereafter, a method is used in which the film is heat-treated while being conveyed while gripping both ends (edges) of the film in a high-temperature furnace at a temperature of 250 to 450°C.

In such conventional methods, a solution casting drying device and a heat treatment device are generally installed in combination, and the process from the casting process to the heat treatment process is integrated to rationally produce polyimide film. ing.

Currently, polyimide films are highly rated as being the most excellent films in terms of heat resistance, but they are expensive and are used only for limited purposes. Therefore, in order to reduce the manufacturing cost of polyimide films, measures have been taken, such as increasing the manufacturing width of the film or increasing the manufacturing speed.

[Problem that the invention seeks to solve]

However, all of these methods have limitations because they involve a significant increase in equipment costs. Furthermore, if capital investment becomes excessive, product prices must be kept high.

The present invention aims to improve the current manufacturing method and provide an economically more advantageous manufacturing method.

[Means for solving problems]

The method for producing a polyimide film of the present invention involves casting a polyimide solution or a polyamic acid solution onto a substrate, and heat-treating the film obtained by drying.At least two or more films are simultaneously fed into a heat treatment furnace, and each It is characterized in that the film is heat-treated with a gap of at least 5 m or more.

The polyimide film of the present invention has a structure represented by general formula (1).

Here, R1 represents a tetravalent aromatic group, and R2 represents a divalent aromatic group or an aliphatic group. Specifically, (1) is a tetracarboxylic dianhydride containing R1 such as pyromellitic dianhydride, 3.3', 4.4'-biphenyltetracarboxylic dianhydride, and 4,4'-diamino It is obtained as a reaction product with Rt-containing diamines such as diphenyl ether and para-phenylene diamine.

The polyimide solution of the present invention is made of a polymer having the above structure. It is 8 liquids.

Further, the polyamic acid solution is a solution of polyamic acid (I[), which is a precursor substance of polyimide (1).

HOH Here, polyamic acid (II) is converted into polyimide by a dehydration reaction.

These polyimide or polyamic acid solutions include
Additives such as a lubricant, an antioxidant, a coloring agent, and a conductivity imparting material can be added as necessary. In addition, other heat-resistant resins such as polyether sulfone, polysulfone,
It is also possible to mix resins such as polyarylate, polyphenylene sulfide, and polyetherimide.

Examples of organic solvents used in the present invention include N, N-
Dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, p-chlorophenol, m-chlorophenol, p-cresol,
Commonly known compounds such as m-cresol, dimethylsulfone, tetramethylsulfone, and dimethylsulfoxide are used alone or in combination of two or more. Furthermore, it can also be used in combination with a non-solvent such as benzene, toluene, xylene, dioxane, cyclohexane, acetone and the like.

As a method of casting a polyimide solution or a polyamic acid solution onto a substrate, most commonly a method such as a die coater or a roll coater is used.

A metal substrate such as a stainless steel substrate is used as the substrate, but a plastic film can also be used as the substrate.

The polymer solution cast onto the substrate is dried in a drying oven and then peeled off from the substrate. The peeled film usually still contains some solvent. If the solvent is completely removed, the peelability of the film from the substrate will be extremely reduced, uneven peeling force will occur, and a film with a smooth surface will not be obtained.

The dry film is heat treated in the next step. In the present invention, at least two or more dry films are simultaneously put into a heat treatment furnace and heat treated while gripping both edges of each film. At this time, each film is arranged so that it has a small gap (in each case, 5 or more gaps). This is to completely remove the solvent that evaporates from the film during heat treatment and the moisture generated due to the imide ring-closing reaction from the film surface. This is to create the voids necessary for the film to be removed.If the films are close to each other, the evaporated gas will not escape sufficiently from the film surface, and will remain at a high concentration, which may cause may condense, which is undesirable.This effect can be sufficiently eliminated by opening the respective film gaps 51-.

Methods for holding the film in the heat treatment furnace include using clips and inserting the film into pins, but the clip method has a large yield loss, so pins are used in most cases. When using pins, two or more dry films can be inserted into the pins at the same time, or the insertion positions can be shifted and the films can be inserted one after another. An example of this method is shown in FIG.

The film that has passed through the heat treatment furnace is sequentially opened at its selvage gripping portions, the tightly attached selvage portions are cut and removed, and then each film is separated and wound up to form a product.

In FIG. 1, the heat treatment furnace is of a horizontal type, but is of course not limited to this, and can be of various types, such as a vertical type or an inclined type.

When the present invention is considered from an economic point of view, it can be said that it is an extremely significant method. That is, according to the inventors' considerations,
Of the amount of heat consumed in a heat treatment furnace, the amount of heat received by the film itself is only 5 to 10%. other 90~9
5% of the energy is carried away with the hot air discharged outside the system or used to heat the heat treatment furnace body. Therefore, as in the present invention, even if the amount of dried film charged into the heat treatment furnace increases, the energy consumption of the entire heat treatment process increases only by a minimal amount. Also,
By implementing the present invention, it is possible to heat treat multiple films without making the heat treatment furnace particularly large.
Productivity is greatly improved.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

2 of polyamic acid obtained by equimolar reaction of pyromellitic dianhydride and 4.4 diaminodiphenyl ether.
A 0% by weight dimethylacetamide solution was cast onto a stainless steel belt using a slit die, and dried at 120°C to obtain a dry film with a thickness of 38 μm and a width of 600 m.

This dry film had a solvent content of 28% by weight measured at 350°C. Next, the two dry films were put into a heat treatment furnace with a structure using pins as a gripping method, as shown in Figure 1, with a distance of 5 mm from each other, and the film was heated to a maximum temperature of 4 mm.
A polyimide film of 26 μm was obtained at 00°C. On the other hand, when two films were put into a heat treatment furnace in close contact with each other, a liquid with a solvent odor, which was an evaporated component, was condensed between the films.

〔Effect of the invention〕

Since the method of the present invention allows a plurality of films to be heat treated in the same heat treatment furnace, it is extremely economical in terms of energy consumption and equipment costs. In addition, there is no condensation of liquid with a solvent odor during the treatment, and there is no harm to the environment, which has a great industrial effect.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a heat treatment method as an embodiment of the present invention. Explanation of symbols 1 Heat treatment furnace 2 Pin 3 Drying film 4 Product film (unwinding)
(Take-up) 5 Pinning brush roll

Claims (1)

[Claims] 1. When heat-treating the film obtained by casting a polyimide solution or polyamic acid solution onto a substrate and drying it, at least two or more films are simultaneously fed into a heat treatment furnace, and each film has a thickness of at least 5 mm or more. A method for producing a polyimide film characterized by heat treatment in a state with gaps.