JPH047130A - Heat treatment of aromatic polyamide film - Google Patents

Abstract

PURPOSE:To obtain industrially a film-excellent in dimensional stability at high temperature by post-treating the aromatic polyamide film with specified thermal characteristics under the condition of specified heat treatment. CONSTITUTION:In order to prevent the flatness of a film from being deteriorated in heat treatment, the aromatic polyamide film which has at most 3.0% of heat-shrinkable ratio and at most 4.5X10<-5> (1/ deg.C) of the thermal expansion coefficient, and is continuously produced, is used, and low heat shrinkable ratio is obtained by the post-treatment under the condition of the heat treatment defined by formulas 1, 2, 3. As the method of heat treatment, the heating method in which a long film in continuously run through the heating furnace such as the dryer of a coating device and is heated, and the heating method in which the film wound up in a roll-shape is directly put and heated in a hot blast oven, etc., are used. Then the tension of the film must be at most 0.5 (kg/mm<2>). Thus the obtained aromatic polyamide film has sufficient dimensional stability at the temperature of reflow solder as flow solder etc., and it is preferably used as electric insulating material, especially as material for FPC.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for heat treatment of aromatic polyamide films, and more specifically to a method for heat treatment of aromatic polyamide films, and more specifically, a method for processing continuously produced films with a low heat shrinkage rate to the extent suitable for reflow or flow soldering processes. The present invention relates to a heat treatment method for oxidation.

[Prior Art] Aromatic polyamide films have excellent mechanical properties and heat resistance, and have been proposed for application to various electrical insulating materials, and are particularly expected to be used as circuit board materials such as flexible printed circuit boards (FPC). has been done.

Conventionally, polyimide films have been widely used as insulation films that require heat resistance, and FPs that require solder resistance
Polyimide film is usually used as the C material from the viewpoint of dimensional stability under high temperatures.

[Problems to be Solved by the Invention] On the other hand, although aromatic polyamide films are superior to polyimide films, they are slightly inferior in dimensional stability at high temperatures, so they are particularly suitable for FPCs with detailed circuit patterns.
However, no progress has been made in this regard.

Many heat treatment methods during the film-forming process have been proposed as a method for manufacturing aromatic polyamide films with low thermal shrinkage, but the continuous film-forming process suffers from various stresses due to equipment limitations. It is actually very difficult to eliminate residual strain on the film because it is unavoidable, and it is sometimes impractical as it complicates the film forming process and increases costs. Almost.

Although it is easy to process small-area film pieces on a laboratory level, there are various problems in industrially producing aromatic polyamides and then performing heat treatment as a post-treatment. For example, it is not possible to use the same heat treatment method for long films that are several hundred to several thousand meters long, or that heat treatment can cause discoloration, deterioration, and deterioration of flatness of the film. This only becomes a problem when producing large quantities of film.

In order to solve this problem, the present invention provides a method of heat-treating a previously produced film as a post-treatment in order to industrially obtain an aromatic polyamide film with excellent solder resistance (heat shrinkage rate). The purpose is to

[Means for Solving the Problems] The present invention provides a continuously produced aromatic compound having a thermal contraction rate of 3.0% or less at 250°C and a thermal expansion coefficient of 4.5XIC)5 (1/°C) or less. The polyamide film is formed by formulas (1) to (3)
at the temperature (T 0C) and time (t time) shown in the range of , and under no tension or 0. 5 (kg/m r
d) It is characterized by heat treatment under the following tension.

50t+200≦T≦-25t+300...
Formula (1) 150≦T... Formula (2)
0.01≦t... Formula (3
) The aromatic polyamide film in the present invention has the following formula: NH-Art -NHC-Ar2 -C-NH-A
A film made of an aromatic polyamide polymer containing a repeating structural unit represented by r 3 C either alone or in copolymerized form, and containing the above structural unit in an amount of 70 mol% or more, preferably 90 mol% or more. Here, Arl, Ar2. Ar3 contains at least one aromatic ring, which may be the same or different, and representative examples include the following.

These aromatic rings include those in which some of the hydrogen atoms on the ring are substituted with a substituent selected from a halogen group, a nitro group, a C1-C3 alkyl group, and a 01-C3 alkoxy group, and is selected from -O-, -CH2-, -3o2-, -8--C--C- CH3.

Among the aromatic polyamides mentioned above, those in which benzene rings with amide bonds bonded at the para position account for 50% or more, preferably 70% or more of the total aromatic rings have improved heat resistance and mechanical properties, and have a coefficient of thermal expansion. It is preferable in that the hydrogen atoms on the benzene ring are partially substituted with a halogen group, especially a chlorine group, making up 30% or more of the total aromatic rings.
A polymer having a content of preferably 50% or more is preferably used in order to reduce the humidity expansion coefficient and moisture absorption rate.

The aromatic polyamide film used in the present invention is heated to 250°C.
It is necessary that the heat shrinkage rate at 3.0% or less, preferably 1.5% or less. If the heat shrinkage rate is greater than 3.0%, regardless of the heat treatment conditions and the heat treatment method described below,
Dimensional stabilization through post-processing as in the present invention cannot be applied because the film becomes wrinkled or streaked during heat treatment, and when heat treated in roll form, the film layer buckles, resulting in a significant loss of flatness. Ta.

The coefficient of thermal expansion of the film before heat treatment is 4.5×105
(1/℃) or less, more preferably 4.0 The balance is not maintained, and the same deterioration in film flatness as described above (occurrence of wrinkles, streaks, and buckling) is likely to occur.

The residual solvent in the film is preferably 1.0% by weight or less based on the weight of the polymer, and it is particularly important to prevent blocking of the film (adhesion between films) when heat-treating the film in roll form or in a cut and stacked state. This is preferable from the viewpoint of prevention.

Regarding the residual inorganic salt in the film, the weight of the inorganic salt is 200 ppm in order to prevent the decomposition of the polymer during heat treatment.
The following is preferable, and 15 oppm or less is more preferable.

The aromatic polyamide film used in the present invention is produced by a known solution casting method. This solution film forming method includes dry, wet, and wet-dry methods depending on the method of solvent removal, but is not particularly limited. Furthermore, during film formation, the film is usually stretched by about 1.0 to 5.0 times in the longitudinal and width directions and heat set at 250 to 350°C, and these operating conditions are used in the present invention. Equally important in determining the properties of aromatic polyamide films is the composition of the polymer. Generally, the higher the stretching ratio, the higher the thermal contraction rate and the lower the thermal expansion coefficient, and the higher the heat setting temperature, the lower the thermal expansion coefficient. Therefore, in the present invention, it is necessary to use an aromatic polyamide film having predetermined physical property values selected from various combinations of polymer composition and film forming process conditions.

The continuously produced aromatic polyamide film can be post-treated under the heat treatment conditions specified in the present invention to have a low heat shrinkage rate.

If the combination of heat treatment temperature (T °C) and time (t time) satisfies the following formula (%) at high temperatures and for long periods of time, the film is likely to become discolored, and furthermore, the film may become brittle due to partial decomposition of the polymer. This is unsuitable because it causes the formation of turbidity, and it is also undesirable because the flatness of the film deteriorates. On the other hand, if the temperature and time are low and short enough to satisfy the following formula 7%, reflow soldering is 200 to 250°C, flow soldering is 24
The object of the present invention, which is achieved by an effective low thermal shrinkage rate in the solder mounting process of 0 to 280°C, cannot be achieved.

Specific methods for heat treatment include heating a long film by continuously running it in a heating furnace such as a dryer in a coating equipment, and heating the film by winding it into a roll directly. There are methods such as heating the film by placing it in an oven or the like, or heating the film by cutting and stacking it in a hot air oven or the like.

When a film is run in a heating furnace, there is no tension in the width direction, but the film cannot run in the longitudinal direction unless some tension is applied. The tension at this time is 0. 5 (kg/mm) or less, preferably 0.1
(kg/mi) or less, and if the tension is too large, not only will the effect of lowering the thermal shrinkage rate not be sufficiently obtained, but also problems such as longitudinal folds will occur in the film.

When heat treating a long film wound into a roll,
The tension during winding is 0. 5 (ks/mar) or less, preferably 0.5 (ks/mar) or less. 2 (ks/mm) or less,
This is necessary for the same reason as above. In particular, when heat-treating rolls, a phenomenon called buckling occurs, where a part of the roll's outer periphery appears to have sunk inward. It is effective to use a material that has a low softening temperature, such as a polyethylene film, wrapped around the core in advance, or to remove the core before heat treatment.

The method of stacking tens to thousands of sheets of cut long film and heat-treating them is in a tension-free state, but if the treatment is performed under conditions other than those specified in the present invention, wrinkles may easily occur and good flatness may not be achieved. It cannot be maintained. This first became clear when attempting to industrially process a large amount of film, and the situation is essentially different from heat-treating one or two films at an experimental level.

The heating method is generally hot air heating, but other heating methods such as near infrared rays, far infrared rays, etc. may also be used, and there is no particular limitation. Regarding the heating atmosphere, an inert gas such as nitrogen is more preferable than air in terms of preventing oxidation of the polymer.

The aromatic polyamide film heat-treated as described above has sufficient dimensional stability even under the temperatures of reflow soldering, flow soldering, etc., and is suitably used as an electrical insulating material, particularly as a material for FPC.

[Characteristics evaluation method] The method for evaluating characteristic values of the present invention is as follows.

(1) Heat Shrinkage A film sample with a width of 10 mm and a sample length of 200M was heat treated in a hot air oven at a predetermined temperature for 10 minutes without any load, and the heat shrinkage was calculated using the following formula.

Thermal contraction rate (%) Q) Using a thermal expansion coefficient thermomechanical analyzer (TMA), the film was heated to 150°C and then gradually cooled to remove the effects of thermal contraction and moisture absorption and desorption. It was calculated from the amount of dimensional change in the range between 150°C and 150°C.

[Example code] The present invention will be explained based on examples.

Example 1 2-chloro-paraphenylenediamine and 0.8 molar ratio of 2-chloro-paraphenylenediamine in N-methylpyrrolidone (NMP). 2
4,4'-diaminodiphenyl ether corresponding to a molar ratio was dissolved, and 2-chloro-terephthalic acid chloride corresponding to a 0.8 molar ratio and terephthalic acid chloride corresponding to a 0.2 molar ratio were added thereto. The polymerization was completed by stirring at a temperature of 30 to 50° C. for 2 hours. An equivalent amount of calcium carbonate was added to the generated hydrogen chloride to neutralize it, thereby obtaining an aromatic polyamide solution with a polymer concentration of 12% by weight and a viscosity of 4100 voids.

This polymer solution was cast on a stainless steel endless belt and heated with hot air at 170° C. for 1.8 minutes to dry the solvent, and the film that had obtained self-retention properties was continuously peeled off from the belt. The peeled film is then introduced into a water bath at 50°C to extract the remaining solvent and inorganic salts generated during neutralization, and then introduced into a tenter where water is dried and heat treated to create an aromatic film with a thickness of 20 μm. A group polyamide film was obtained. During this step, the film was stretched by 1.15 times and 1.25 times in the longitudinal and width directions, respectively, and heat treated at 310°C for 1.25 times.
It was 5 minutes.

The physical property values of the obtained film were a heat shrinkage rate of 1.4% and 1.2% at 250°C in the film longitudinal direction and width direction, respectively.
, thermal expansion coefficient 1.6×10-5 (1/℃), 1.7x
It was lO' (1/°C). Further, the amount of residual solvent in the film was 0.02% by weight, and the amount of residual inorganic salts (Ca, Na, etc.) was 2 appm.

The long aromatic polyamide film produced continuously as described above was passed through a heating furnace of a continuous coating apparatus and subjected to heat treatment.

The heating furnace temperature was 240°C, the heating time was 1.1 minutes, and the tension on the film was 0. 06 (kg/mu?). The physical properties of the film after heat treatment are: thermal contraction rate at 250°C of 0.7%, 0.6%, thermal expansion coefficient of 1.7xlO' (1/°C), 1.7xlO in the longitudinal direction and width direction, respectively.
' (1/°C), and the dimensional stability was good. Furthermore, no wrinkles or streaks were caused by the heat treatment, and good flatness was maintained.

In addition, an aromatic polyamide film was wound around a paper core with a diameter of 6 inches and the tension was 0. 2 (ks/mm) and roll it up to 300m in a hot air oven from room temperature to 230m.
The temperature was raised to 0.degree. C. over 1 hour, and heat treatment was continued at the same temperature for an additional 0.5 hour.

Furthermore, 200 sheets of the film cut into 500 wafers were stacked together, placed in a hot air oven, and heat treated at 230° C. for 2 hours.

Thermal shrinkage rate at 250℃ after heat treatment (longitudinal direction, width direction)
, the heat-treated product in roll form was 0.5%, 0°4%, and the cut product was 0.3%, 0.3%, resulting in very good dimensional stability, and both films had good flatness. Met.

Comparative Example 1 The aromatic polyamide film prepared in Example 1 was heat treated under the following conditions.

Condition A: Run the film in the heating furnace of the coater for 15 minutes.
Heat treatment at 0°C for 30 seconds.

Tension is 0. 06 (ke/mff1).

Condition B: Run the film in the heating furnace of the coater for 30 minutes.
Heat treatment at 0°C for 2 minutes.

Tension is 0.06 (k8/mm).

Condition C: Rolled in a hot air oven at 270°C, 3
Heat treatment for hours.

Under condition A, the heat shrinkage rate was 1.4%, 1.2% (longitudinal direction,
(width direction) had no effect at all. Under condition B, the heat shrinkage rate was 0.4%, 0.4%, but the film was colored considerably brown, and under condition C, the heat shrinkage rate was very small, 0.2%, 0.1%. However, the film appeared to be severely colored and brittle, and the roll buckled, resulting in poor flatness.

Comparative Example 2 2-chloro-paraphenylenediamine corresponding to a molar ratio of 0.6 and 0.6 molar ratio. The diamine component is 4,4-diaminodiphenyl ether corresponding to a molar ratio of 4,4, and 2-chloro-terephthalic acid chloride corresponding to a molar ratio of 0.8. 2
A film with a thickness of 16 μm was formed using the same polymerization and film forming method as in Example 1 from isophthalic acid chloride corresponding to the molar ratio. However, the stretching is 1.05 times, 1.17 times (longitudinal direction,
(width direction), and heat setting was performed at 320° C. for 1.5 minutes.

The physical properties of the obtained film were a thermal shrinkage rate of 2.7% and 2.4%, and a thermal expansion coefficient of 5.0% in the longitudinal direction and width direction, respectively. l
Xl0'''5 (1/℃), 5.1×10-' (1/
℃). When this film was heat treated in roll form in the same manner as in Example 1, there were many buckles and wrinkles and the flatness was very poor.

In addition, the physical properties of films made from the same raw materials under the conditions of stretching ratios of 1.25 times and 1.30 times and heat setting at 290°C for 1.5 minutes are as follows: heat shrinkage rate of 3.8%, heat shrinkage of 3°6%, Expansion coefficient 3
．． 6X10''6 (1/℃), 3゜4xlO'5 (
1/°C). When this film was heat treated in roll form in the same manner as in Example 1, buckling and wrinkles occurred and the flatness was severely impaired.

[Effect of the invention] In the present invention, by post-treating an aromatic polyamide film having specific thermal properties under specific heat treatment conditions, it is possible to industrially produce an aromatic polyamide film with excellent dimensional stability under high temperatures. and can be provided without compromising other qualities.

Claims (1)

[Claims] Thermal contraction rate at 250°C is 3.0% or less, and the thermal expansion coefficient is 4.
．． A continuously produced aromatic polyamide film of 5×10^-^5 (1/℃) or less is heated at a temperature (T℃) and a time (t time) shown in the range of formulas (1) to (3). A method for heat treating an aromatic polyamide film, characterized in that the heat treatment is carried out under no tension or under a tension of 0.5 (kg/mm^2) or less. -50t+200≦T≦-25t+300...
Formula (1) 150≦T・・・Formula (2) 0.01≦t・・・Formula (3)