JPS60190313A - Manufacture of polyimide film - Google Patents

Abstract

PURPOSE:To obtain a polyimide film with lesser surface defects by a method in which a solution of polyamide in an organic solvent is mixed with an imidization catalyst and a dehydrating agent, and the mixture is cast on a supporter, dried and heat-treated under a specific condition. CONSTITUTION:A solution of polyamide in an organic solvent is mixed with an imidization catalyst (e.g., pyridine, isoquinoline, etc.) and a dehydrating agent (e.g., acetic acid, propionic acid, etc.). The mixture is cast on a supporter and dried in the early period only by heat conductance from the supporter by heating the supporter to 40-200 deg.C in such a way as to thicken the surface of the solution film. The solution film is then dried forcibly by blowing hot air, and the film having a self-supporting property is heat-treated to remove the remaining solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-resistant film, and particularly to a method for producing a heat-resistant film that has no or very few surface defects such as pinholes, ridges on the surface of protrusions, and foreign matter adhesion. It is.

More specifically, a polyimide obtained by mixing and adding a tertiary amine imidization catalyst and an acid anhydride dehydrating agent to a polyamic acid organic solvent solution is used to produce a heat-resistant film with no or very few surface defects. It relates to a manufacturing method.

Conventionally, heat-resistant films such as polyimide have excellent physical properties over a wide temperature range, and films are manufactured using extrusion and mid-stream processing methods. It is widely used for wire films, 4Z films for electric wires and cables, ground insulation materials for transformers, capacitor vapor films, etc. Furthermore, recently it has been expected to be applied to high surface quality films, such as base films for magnetic recording materials.

In the casting method, a polyamic acid organic solvent solution is generally cast from a T-die onto a support such as a stainless steel ingot belt or a metal drum, and pre-dried (by hot air drying, etc.) until it becomes self-supporting. Then, the self-supporting film was peeled off from the support, and the pre-dried film was evaporated using a pin tenter or a clip tenter to remove residual solvent and promote imidization. The contact surface with the support has so-called surface defects such as unevenness and corrugation, which hinders the expansion of a wide range of application fields, including applications to high surface quality films such as base films for magnetic recording materials. ing.

The present inventors have conducted various studies on ways to improve the drawbacks of such conventional methods, and have come up with the idea.

That is, the gist of the present invention is to mix an imidization catalyst and a dehydrating agent into a polyamic acid organic solvent solution.

3- The mixed solution is cast onto a support, and first, the casted mixed solution is subjected to heat transfer only from the support, and by initial drying, the surface of the solution film is exposed to hot air. The viscosity is increased to a state where it does not deform by spraying, and then forced drying is performed by blowing hot air to obtain a pre-dried film with high self-supporting properties.When further heat treatment is applied, K. The present invention relates to a method for producing a polyimide film characterized by removing residual solvent of the polyimide film.

The present invention will be explained in detail below.

The polyimide film of the present invention is characterized by repeating units having the following structural formula.

(However, R is a Z-valent organic group.
4- is an organic group) The polyamic acid used in the production of the polyimide film in the present invention has a repeating unit (
However, in the formula, R is a y-valent organic group, R/ is a monovalent organic group), and N, N
- Briquettes of θ, jt/dJ in dimethylformamide and 3
The logarithmic viscosity (ηinh) determined by II at 0°C is at least o
, s di / f. Logarithmic viscosity is θ, odi/f
This is because if it is smaller, only a film with inferior strength can be obtained.

Here, the logarithmic viscosity (ηinh) is the following formula 4 (%)) (In the formula, O is the concentration of the polymer solution (polymer 2/solvent 10θd
), and ηreJ is the measured value defined as the relative viscosity, i.e. the ratio of the flow time of the combined solution and the solvent measured with a capillary viscosity needle. θ Tajita, same 3! -♂2! Manufactured using the method published in θgin. That is, the structural formula % formula % (wherein R1 is 4 containing at least one carbon atom)
and a structural formula (provided that the formula R is a divalent group containing at least 2 carbon atoms, and the carbonyl group of the dianhydride is not bonded to one or more carbonyl groups to each of the 7 carbon atoms of the dianhydride group. ) of a tetracarboxylic dianhydride having at least 10% of the total temperature during the reaction in an organic polar solvent under anhydrous conditions, preferably below 10°C! It consists of carrying out the reaction while maintaining the temperature below Q°C.

The obtained polyamide H solution is used for producing a polyimide film as described below. Conversion of polyamic acid to polyimide can be carried out thermally or chemically, but in the present invention chemical imidization is carried out. That is, imidization is carried out using a dehydrating agent and an imidization catalyst together.

Dianhydrides that are not suitable for use in the present invention include:

Pyromellitic dianhydride, 3. Kimigu, nail-diphenyltetodicarboxylic acid dianhydride e 31 ``e'' a nail-λ
1.2'-Bis(3,4t-dicarboxyphenyl)p7-tetravandianhydride, bis(3,4t-dicarboxyphenyl)ether dianhydride, ethylenetetracarboxylic dianhydride, Schiff tetrapentanetetracarboxylic These include acid dianhydrides.

As diamines suitable for use in the present invention.

m-phenylenediamine, p-phenylenediamine, 4
t, 4t'-cyabanoliphenylpropane, 4t.

Nail-diaminodiphenylmethane, 4t,4t'-diaminodiphenyl ether, 0-)lysine, 0-dianisidine, /,j-diaminonaphthalene, p,4t'-diaminodiphenyl sulfide, \,\'-cya-based nodiphenyl sulfone Can be mentioned.

Solvents useful in synthesizing the boriaodo acids of this invention are organic polar solvents whose functional groups have a dipole moment that does not react with the diamine or dianhydride. The organic polar solvent must be inert to the reaction system and must be a solvent for the product and at least for the reactants and preferably for both reactions. Preferred solvents include N,N-dimethylformamide, 8-N,N-dimethylacetamide, N-methyl-pyrrolidone, tetramethylenesulfone, dimethylsulfone,
Examples include pyridine. Solvents may be used alone or in combination, or benzene, toluene, xylene, dioxane,
It can be used in combination with a non-solvent such as butyl lactone or cyclohexane.

The dehydrating agent and imidization catalyst used in the present invention are not particularly limited, but the following compounds are usually used.

Dehydrating agents include aliphatic and aromatic carboxylic acid anhydrides such as acetic acid, propionic acid, isobutyric acid, benzoic acid, propylbenzoic acid, and toluic acid.Dehydrating agents are usually added to the acid component unit in polyamic acid. The imidization catalyst is used in an equimolar proportion or more.
Inquinoline, 3. ! -lutidine, methylpyridine, and 3-methylpyridine. The imidization catalyst is usually used in a ratio of about 0.6 to 2 mo1 to the acid component unit in the polyamic acid.

Next, a specific example of the film manufacturing method will be explained.

First, two types of solutions are prepared: a dehydrating agent system in which a dehydrating agent such as an acid anhydride is mixed in advance with a polyamic acid-like solvent solution, and a catalyst system in which a third IfIi amine imidization catalyst is mixed.

The dehydrating agent type and catalyst type 1281 class polyamic acid organic soluble solutions are each individually charged into a supply tank.

Then, for example, as a defoaming operation.

While stirring the solution with a stirring blade rotating at a low speed of 1 to 30 revolutions, air bubbles in the solution are completely defoamed by reducing the pressure in the supply tank with a vacuum pump. Next, the 12 kinds of solutions of the dehydrating agent system and the catalyst thread are each individually supplied into the mixer by pressurization or a gear pump. The mixer used here is usually called a continuous in-tube mixer, but the
In an extremely short time of ~/θ seconds, the number of divided layers is 3×101
' or more, preferably /x/θ6 or more. If the number of divisions is less than 7.3×70'', defects due to uneven mixing may occur, which is not preferable. The solution quickly and uniformly mixed by the mixer is sent to a T-die, etc., and the slit gap is inserted into a metal such as stainless steel that has been cooled and maintained at room temperature/l to 30°C in advance from the prepared lip. It is cast onto a support of maple belt or metal drum width. Here, if the support temperature is higher than the above mixed carbon,
The organic solvent evaporates at the same time as the a-spreading process, which may cause problems with the noodles.

Examples include: (1) change in the surrounding atmosphere, (1) gradual dew of solvent in a casting molding device such as a T-die, and occurrence of uneven defects on the surface of the film after evaporation. Then, as initial drying in the m1 drying step, the support is imidized. This initially dried liquid film is thickened by blowing hot air to a level where the Fi surface morphology is not deformed.

This will require a long period of time. Further, when the temperature 11- of the support body exceeds 200°C, defects such as bubbles are generated in the casting liquid film due to the rapid temperature rise.

It is not possible to obtain a film with an extremely smooth surface. On the other hand, in order to obtain a film with a smooth surface, it is desirable to use clean air of class 700 or higher, or a mixture thereof, as the atmosphere for the initial drying, and this atmosphere is forced to flow in the area where the initial drying is performed. It is in a state of natural flow, such as relative gas flow near the surface of the liquid film as the support moves and natural convection of atmospheric gas caused by the heat of the support. That is, the initial drying is performed only by heat conduction from the active support.

Here, if the atmospheric gas in contact with the liquid film surface is forced to flow, such as by blowing air or nitrogen gas onto the liquid film surface, unevenness may occur on the liquid film surface.

This will adversely affect the surface morphology. Initial drying is carried out under such conditions, but it is convenient to carry out the initial drying until the solution thickens to the point where it does not deform even when hot air is blown onto the surface of the solution film.

Next, in order to have self-supporting properties as a film,
The air is sprayed onto the surface of the thickened liquid film using a slit nozzle having an air volume gradient of 00 to λjio°C, preferably 720 to m/s, increasing stepwise in the direction of movement of the film.

A pre-dried (half-dried) film containing an appropriate amount of residual solvent is obtained. If the temperature of the blown hot air is below 700° C., it will take a significant amount of time for drying, and as a result, the equipment will become extremely large or the production rate will be reduced. On the other hand, 26
If the temperature exceeds 0°C, defects such as bubbles will occur in the film.

On the other hand, if the hot air blowing speed pattern does not have an air volume gradient that increases sequentially and is constant at less than /~jrn/s, it will take a significant amount of time for drying, which will cause problems. Also! ~7.2m/s or /2~2
If the velocity is constant at 0 m/s or more, it may cause negative effects such as unevenness on the surface of the liquid film.

The thus obtained self-supporting drying film is peeled from the support and then passed through a heat treatment furnace, with both ends of the film supported by a conventional heat treatment device such as a binder or clip tenter. 〇θ～10
Heat-treated at about θ°C, residual bath residue is removed, and a heat-resistant film with no or very few surface defects is produced! ! Threaded.

According to the present invention, as described above, an excellent film without surface defects can be obtained and used as a base film for magnetic recording media. The term "film" includes thick films, ie, those called sheets.

The present invention will be further explained with examples below.

The present invention is not limited to the following examples which do not go beyond the gist of the invention.

(hereinafter abbreviated as ODA) Yaza, i' kg, N, N
-dimethylformamide (hereinafter abbreviated as DMF),
29.3 kg was charged and stirred for 7 hours to completely dissolve ODA. Then PMDA
)2. After adding 9 little by little at θ≦, the reaction temperature was maintained at 20°C.

The reaction was carried out under stirring for 70 hours, and the viscous polyamic acid was measured to have a lambda of 7 di/f.

Reference example / Reference example / In place of ODA, ODA θ, tough 9 and 〇-tolidine (hereinafter abbreviated as OTD) 0.9 def
The same reference was made except that kg of mixed diamine was used.

16 one Example/ 7.05 kg of the polyamic acid solution obtained in Reference Example/.

to acetic anhydride, y3 kg and dimethylformamide (DM
'IP) 3.9 was charged into a mixing tank AK equipped with a stirring device and a cooling jacket. In a similar mixing tank B, 3 kg of the polyamic acid bath solution R obtained in Example 1, yikg, Inquinoline O, and DMF 3.3 were charged with 9. Next, while cooling the internal solution by passing a refrigerant at about f° C. into the jacket of the stirring tank, the mixture was stirred under reduced pressure for 3 hours to defoam and form a homogeneous solution.

Next, the polyamic acid solutions in the stirring tanks A and B, which have been damped as described above, are continuously passed through a 2 μm cut gold filter using a metering bong, respectively, and then separated into one divided layer @2. /X/θ
While continuously mixing in a short time (approximately 1 second), the distance between the lips and the length in the width direction of the lips θθ' is approximately ! cooled to ℃. A liquid film was formed by extruding from the lip of a T-die mold onto a rotating belt maintained at approximately 20°C. Next, the belt was heated with hot air at 700°C from below the belt, creating a class/θ0 clean air atmosphere above the liquid film.

Then /θθ℃, /20℃, /! The top and bottom of the belt moving hot air at 0°C are 2 m/s each.

J'm/8. After sequentially blowing hot air at a speed of /j m/B, it was continuously peeled off and fixed to a rotating pin tenter. The pre-dried film at this time was 2!
It contained volatile components of chi. 2 continuously while moving the fixed pre-dried film! θ℃.

A dry polyimide film was obtained by passing through a heat treatment zone consisting of a temperature range of 3θθ°C, J, tO″C, 300°C and 1.2jO°C.

The tensile properties of this film were an initial modulus of elasticity of 270/2 strength/1/2 and an elongation at break of 0/1.

In addition, no defects such as scratches or pinholes were observed in a microscopic photograph of the surface of the film.

Example λ A polyimide film was obtained in exactly the same manner as in Example 1, except that the polyamic acid solution obtained in Reference Example λ was used instead of the polyamic acid solution obtained in Reference Example 1.

The tensile properties of this film are initial elastic modulus≦jθkg/11
121 strength 33kg7 2. The elongation at break was 3θ.

Also, a microscopic photograph of the film surface shows protrusions.

The defects of the pinhole team could not be overcome.

Sender: Mitsubishi Chemical Industries, Ltd. Representative patent attorney - (7 others) 19- 58-

Claims (4)

[Claims] (1) An imidization catalyst and a dehydrating agent are mixed in a polyamic acid organic solvent solution, and the mixed solution is cast onto a support. First, the support is heated to yθ to 200°C, and the mixture is nuclear-cast. By initially drying the solution only by heat conduction from the support, the surface of the solution film is thickened to a state where it will not be deformed by hot air blowing, and then by forced drying by hot air blowing, it becomes self-supporting. 1. A method for producing polyimide 7, which comprises obtaining a pre-dried film having the following properties and further removing residual solvent in the pre-dried film by heat treatment. (2) When mixing a polyamic acid organic solvent solution, an imidization catalyst, and a dehydrating agent in a continuous tube at /~/θsec, a mixed solution is prepared in advance by separately mixing the imidization catalyst and dehydrating agent with the polyamic acid organic solvent solution. 2. The method for producing a polyimide film according to claim 1, wherein the two mixed solutions are mixed in a continuous tube mixer with a number of divided layers/3 x /θ5 or more. (3) When casting the mixed solution onto a support, the temperature of the support surface before the casting position is set to 1 to 30°C. A method for producing a polyimide film according to item 1. (4) When the initially dried and thickened liquid film is forcedly dried by blowing hot air, the hot air blowing speed pattern is made to have a gradient in the direction of movement of the liquid film rather than gradually increasing. The method for producing a polyimide film according to any one of Items 7 to 3.