JPH04148917A - Forming method of low heat-shrinkable polyphenylene sulfide film - Google Patents

Abstract

PURPOSE:To obtain a forming method of film made of polyphenylene sulfide, the heat shrinkage factor of which at the temperature higher than the heat treatment temperature is small and the color change of which is little, by a method wherein a process, in which stretch heat treatment is carried out at the temperature not more than the specified one, and a process, in which relaxation heat treatment is carried out without substantially being received by mechanical external stress within the specified temperature range, are provided. CONSTITUTION:Unstretched film made of polyphenylene sulfide, which is obtained by melt extrusion molding, is stretch-heat-treated at the temperature, which is higher than its crystallization temperature and lower than its crystalline melting point by 20 deg.C. After that, the resultant film is relaxation-heat-treated within the temperature range, at which the lower limit temperature is set to be either higher one of the temperature lower than the stretch heat treatment temperature by 60 deg.C and the crystallization temperature and the upper limit temperature is set to be the temperature lower than the crystalline melting point by 20 deg.C, without substantially being received by mechanical external stress. As for the obtained film, its color change can be suppressed as compared with the conventional film and its heat shrinkage factor can be reduced to a far greater extent.

Description

DETAILED DESCRIPTION OF THE INVENTION ``Industrial Application Field'' The present invention relates to a method for forming a film having an extremely low heat shrinkage rate made of polyphenylene sulfide.

1-Prior art] For example, in an insulating film in which conductors are laminated, such as in a printed circuit board, when the reflow semi-rD is melted with a hot wire in the manufacturing process, the resin constituting the insulating filler is heated to a temperature of 230 to 240°C. It can be heated up to. 1 At that time, the insulating film (usually stretched and heat-set, but heat shrinkage still occurs.As a result, the conductor that should be unseparated is wired through a small gap. Mutual contact may occur and the flatness may be impaired.The higher the integration density of the conductors on the printed circuit board, the lower the thermal shrinkage rate is desired.

In addition, a release film is used to prevent the adhesive exposed by etching during the printed circuit board manufacturing process from adhering to areas other than the printed circuit board until it hardens.

When this peeling film is subjected to thermal history while stacked on the printed circuit board, the conductive portion of the board will be deformed if it undergoes thermal deformation that is different from that of the insulator of the board. Therefore, this release film is also required to have the same heat shrinkage rate as the printed circuit board.

In addition, low heat shrinkage is required in many other fields, such as floppy disks, TAR tubes, sliding members used in conjunction with insulating films or metal plates.

On the other hand, various resins are known as heat-resistant resins that can be used even at such high temperatures, but they are heat-resistant, have excellent productivity, and are relatively inexpensive as a result. Polyphenylonone sulfide is attracting attention as a resin. Among these, conventional methods for forming films with a low heat shrinkage rate include, for example, the Japanese Patent Publication No. 64. -7579
At a higher temperature than the temperature at which unoriented amorphous Filnault is used as shown in the publication, in this example 260°C.
, a method of constant length heat treatment has been adopted. However, the heat shrinkage rate obtained with this method is the crystal melting point of 285
It is about 0.3% at most at 250°C, which is relatively close to 250°C. Moreover, thermal degradation occurs at such high temperatures.

On the other hand, as an example of the heat shrinkage rate at a temperature higher than the heat treatment temperature, there is also an example in Japanese Patent Publication No. 64-7579, but the heat shrinkage rate at 250℃ after heat treatment at 130℃ is 0.7%.
It's just that.

As described above, a method for forming a polyphenylene sulfide film with a low heat shrinkage rate and little thermal deterioration, which can be made to have a heat shrinkage rate of about 0.6% or less even when used at a temperature higher than the heat treatment temperature, is conventionally known. There wasn't.

[Problem to be Solved by the Invention (1) An object of the present invention is to provide a method for forming a film made of polyphenylene sulfide that has a small heat shrinkage rate at a temperature higher than the heat treatment temperature and less discoloration.

Another object of the present invention is to provide a method for molding FILNO which has a smaller heat shrinkage rate at a temperature lower than the heat treatment temperature and which causes slight discoloration.

1 Means for Solving Problems 1 <Summary> The gist of the present invention is to process an unstretched film made of borifunilene sulfide obtained by melt extrusion at a temperature higher than the crystallization temperature and 20°C below the crystal melting point. A step of performing stress heat treatment at a low temperature or lower, and then (b) a temperature in which the lower limit temperature is the higher of either a temperature 60 °C lower than the stress heat treatment temperature or the crystallization temperature, and the upper limit temperature is 20 °C lower than the crystal melting point. The present invention provides a method for forming a polyphenylene sulfide film with low heat shrinkage, which comprises a step of performing a relaxing heat treatment without substantially receiving external mechanical stress within a range.

The present invention will be explained in detail below.

<Polyphenylene sulfide film> In the present invention, polyphenylene sulfide 1 to 1 means a polymer having -Ill-8-)- as a main constituent. Here, the main constituent means 50 mol% or more. The amount used is preferably 70 mol% or more, more preferably 90 mol% or more.

The unstretched film made of polyphenylene sulfide referred to in the present invention refers to an unstretched film made of polyphenylene sulfide alone or a composition containing polyphenylene sulfide as two components (-) and blended with other thermoplastic resins and fillers. "Main component" refers to 50% by weight or more. In particular, a composition containing an inorganic substance can further reduce the heat shrinkage rate, and is therefore preferably employed. Also [unstretched
This does not exclude those that exhibit fluid orientation above the crystal melting point. Therefore, the unstretched film 1\ in the present invention may be a fluid oriented film or an unoriented film.

A fluid oriented film can be obtained by using a branched high molecular weight polyphenylene sulfide, melt extruding it, and then rapidly cooling it while taking it off at a high draft rate. Moreover, a non-oriented film can be obtained by a conventionally known method.

In the present invention, first, an unstretched film made of polyphenylene sulfide is obtained by melt extrusion molding. The shape of the film is not limited to a flat plate, but may be cylindrical. Further, the thickness of the film should be 5 mm or more for this thin leaf-shaped molded product. A desired film thickness can be obtained by appropriately selecting the extrusion amount and take-off speed.

The melt extrusion step and the subsequent tension heat treatment step J- may be performed sequentially, or another step such as a cooling step may be interposed between these steps.

For the cooling process, a known method such as casting on a cooled metal drum or passing through a low-temperature fluid may be employed.

Tension heat treatment process> The film obtained by melt extrusion is heated to a temperature higher than the crystallization temperature,
The strain heat treatment is carried out at a temperature not higher than 20° C. below the crystal melting point, more preferably at a temperature not higher than 30° C. below the crystal melting point.

The heat treatment temperature in this step qσ and the following steps both refer to the heating medium temperature for heating the film, and a known heating medium such as a heating roll is suitably used in this step. Crystallization temperature and crystal melting point are the first exothermic peak temperature that appears when polyphenylene sulfide in the form of an amorphous pellet is heated at a rate of 10°C/min from a temperature lower than the glass transition point using a differential scanning calorimeter. This refers to the endothermic vibration during melting. In addition, when polyphenylene sulfide has two or more crystallization temperatures and crystal melting points, such as a resin composition, the main crystallization temperature and crystal melting point are respectively referred to here.

The tension heat treatment is for promoting crystallization at least to some extent while maintaining flatness before the next relaxation heat treatment.

Otherwise, the subsequent relaxation heat treatment will cause large shrinkage and result in poor flatness. The time required for the stress heat treatment depends on the crystallization rate of the polyphenylene sulfide used; if the crystallization rate is low, the treatment is longer, and the higher the degree of crystallinity after the stress heat treatment, the more preferable it is.
It is preferable to treat it to an extent of 0% or more, particularly 15% or more, especially 20% or more.

The stress in the tension state is maintained to such an extent that the shape of the film after stretching can be maintained.

<Relaxation heat treatment step> Next, mechanical treatment is performed within a temperature range in which the lower limit temperature is 60 °C lower than the tension heat treatment temperature or the crystallization temperature, whichever is higher, and the - limit temperature is 20 °C lower than the crystal melting point. Relaxation heat treatment is performed under conditions where the material is not substantially subjected to external stress.

Here, 1 without substantially receiving mechanical external stress]
This does not mean that the film is not subjected to stress from the support that anchors it in the heat medium. For example, when a film is left still in an oven, the friction stress with the stationary surface that occurs due to thermal expansion or contraction, and the stress caused by the film's own weight when the film 1 is hung or the edges of the film are fixed. When the heating medium is a fluid, particularly a liquid, it may be subjected to stress etc. from the heating medium as the film or fluid moves. However, it is preferable to carry out the heat treatment under conditions that minimize stress as much as possible. For example, heat treatment is carried out while holding the edges of the film in an air oven, or the film is left standing in a heating medium with a specific gravity similar to that of the film. The method is preferably adopted.

The higher the heat treatment temperature, the lower the heat shrinkage rate, and the lower the heat treatment temperature, the better the flatness can be obtained. The upper temperature limit is 20 °C lower than the crystal melting point, preferably 25 °C lower than the crystal melting point, and the lower temperature limit is 40 °C lower than the stress heat treatment temperature or the crystallization temperature, whichever is higher; More preferably, the lower limit temperature is a temperature that is 20° C. lower than the tension heat treatment temperature or a temperature that is higher than the crystallization temperature. The heat treatment time may be a time sufficient to relax and loosen the strain caused by the tension heat treatment as well as the strain caused during transition from the tension heat treatment step to the relaxation heat treatment step, and is appropriately selected depending on the heat treatment temperature.

Between this relaxation heat treatment and the preceding tension heat treatment, another -L
There may or may not be any intervention.

(Example) <Measurement method> Heat shrinkage rate: Cut a film into 100 mm in length and width, and stamp a cross with a length of about 1.00 mm on the film before measuring.
A transparent acrylic plate was placed thereon, and the length was measured using a microscope capable of reading down to 1 μm. Next, the acrylic board was removed, the film was placed on copy paper, and placed in a hot air oven at 250°C for 10 minutes.
Ta. Then, after being left to stand at room temperature, the length was measured using a microscope capable of reading down to 1 μm in the same manner as before measurement. The heat shrinkage rate was determined from the average value of the three points by repeating such operations.

Color difference: [1Kiden color -
Measured at TS7.8'722 by the 1' reflection method. The color difference display SM is based on the Hunter's color difference formula of ITS Z8730. The standard is Comparative Example 1.

<Comparative Example 1> 100 parts by weight of polyphenylene sulfide, 0.2 parts by weight of kaolin, and calcium stearate polymerized by a conventional method using 0.2 mol of trichlorobenzene per 1.00 mol of diglorbenzene as an aromatic halide. 0
A composition consisting of 2 parts by weight of .
300 poise, and the crystallization temperature is 127 degrees],
The crystal melting point was 277°C. 16 of the obtained pellets
After heat treatment at 0°C for 30 minutes, 50mmφ, L/D=2
Lip clearance attached to No. 8 extruder 0.5mm
The resin was extruded into a film using a T-die with a lip of 560 mm in width (7) and taken off in an amorphous state using a casting roll. The distance between the T-die tip and the upper end of the casting roll was approximately 10 mm.
Gear sting roll surface temperature is 40℃, Yumitori speed is 1
The speed was set at 5 m/min.

The thickness of the amorphous film j\ is 3811 m. Surface temperature 1
．． The film was passed between a heating roll (diameter 300 mm) with a surface temperature of 180 °C and a heating roll (diameter 3 QO mm) with a surface temperature of 180 °C at a speed of 5 m/min and wound up onto a take-up roll. The time that the sample was in contact with the heating roll (180 mm) was approximately 6 seconds.

The crystallinity of this film was 21%, and in Figure 11, which shows the results of thermal shrinkage and color difference, the horizontal axis indicates the relaxation heat treatment temperature of 25°C.

<Examples 1 to 5> Five sets of three films each of Comparative Example 1 were prepared, and each film was placed on -1- of copy paper without any fixed frame, and one sheet of each film was prepared.
It was left standing in a hot air oven at 50°C, 175°C, 200°C, 225°C, and 250°C for 10 minutes. The heat shrinkage rate and color difference of the film after the treatment were as shown in the figure <Comparative Examples 2 to 4> Three sets of three films each of Comparative Example 1 were prepared and copied without any fixed frame. 125 each on top of
℃, 260°C, and 275°C for 10 minutes in a hot air oven. The heat shrinkage rate and color difference of the film after the treatment were as shown in the figure.

[Effect 1 of the present invention] The present invention has made it possible to significantly reduce the heat shrinkage rate while suppressing discoloration compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 shows the thermal shrinkage rate at a relaxation heat treatment temperature of 250° C. shown in Examples and Comparative Examples, and FIG. 2 similarly shows the color difference therebetween. Procedural amendment (method) February 18, 1991

Claims (1)

[Claims] (1) An unstretched film made of polyphenylene sulfide obtained by melt extrusion molding is subjected to (a) tension heat treatment at a temperature above the crystallization temperature and 20°C lower than the crystal melting point, and then (b) tension heat treatment at the lower limit temperature. A process of relaxing heat treatment without substantially receiving mechanical external stress in a temperature range where the temperature is 60°C lower than the heat treatment temperature or the crystallization temperature, whichever is higher, and the upper limit temperature is 20°C lower than the crystal melting point. Method for forming a low heat shrinkable polyphenylene sulfide film consisting of