JPS62263022A - Method of relaxation heat treatment of thermoplastic resin film - Google Patents

Abstract

PURPOSE:To obtain large heat shrinkage by a method wherein a stretched film is thermoset at a temperature higher than the glass transition temperature of resin by a specified temperature range and both end parts of the film is cut off at a zone in which no film-treating air blows and the resultant film is gradually cooled at a cooling zone, relaxed by reducing the take-off speed of the film, cooled down to normal temperatures and finally rolled up. CONSTITUTION:A longitudinally stretched thermoplastic resin film 1 is preheated at a preheating zone 3 in the state that the side end parts of the film are clamped by the clips of tenter rails, laterally stretched at a stretching zone 4 and successively thermoset at a temperature higher than the glass transition temperature of the resin of the film by the temperature range from 100 deg.C or above to 180 deg.C or below at a heat treatment zone (thermosetting zone) 5 and cooled down by cooling air having said glass transition temperature or above at a cooling zone 6. A zone 7, in which no hot air blows off and cutter facilities 8 and 8' are equipped, is provided so as to cut off both the side parts of the thermoset film. A film both side parts of which are cut off is gradually cooled down at the cooling zone 6 and run in the state being relaxed between the cutters 8 and 8' and a roll 10 by making the take-off speed of the take-off roll 10 slower than the running speed of the clips.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for relaxing heat treatment of a thermoplastic resin film, and more specifically, a method for stably and reliably performing relaxation heat treatment of a thermoplastic resin film heat-set with a tenter. related.

(Prior Art) After a thermoplastic resin film is stretched, it is slit as necessary and subjected to secondary processing.

At that time, the film may be subjected to reheat 9B embedding.
Dimensional stability is required. During secondary processing, the film undergoes heat shrinkage, which can cause problems such as problems in the processing process and a decrease in product yield. Therefore, dimensional stabilization treatment, such as relaxation heat treatment, is usually performed in the film forming process. , a method has been adopted to reduce the heat shrinkage rate of the film.

For the relaxation heat treatment in the longitudinal direction of the film, for example, there is a method in which a heating device is installed between the rolls in the longitudinal direction of the film, and the speed of the take-up roll is slightly reduced relative to the supply roll. The method of gradual relaxation heat treatment (Japanese Patent Publication No. 44-20240g) is 1.
Being talked about.

In the former case, a heating device is usually provided between the rolls to reheat the cooled film, resulting in a large energy loss and requiring additional heat treatment time. On the other hand, in the latter case, the film side edges are also heat-treated in the tenter at the same time, so there is a difference in heat shrinkage between the thick end portions and the thin center portion, causing the film to sag, resulting in poor flatness, etc. On the contrary, there is a problem that the clip speed decreases in the tenter, and the means for gradually decreasing the clip speed in the advancing direction requires complicated equipment, which is disadvantageous in terms of maintenance or loss.

In addition, as a method using a tenter, both ends (clip gripping parts) of the film are cut at the rear of the tenter heat treatment zone, and only the central part of the film is loosened in the vertical direction between the tenter and the winder ( For example,
-54290) is known. However, with this method, not only is it difficult to cut smoothly due to the hot air circulating inside the tenter, but the film temperature at the cutting position is high, and the distance from the cutting position to the take-off system is long, so the film in the center may be sagging. There is a problem in that the film suffers from a lack of running stability and, in some cases, wrinkles in the film running direction.

(Objective of the Invention) An object of the present invention is to provide a method for relaxing heat treatment of a thermoplastic resin film, which improves the above-mentioned problems and also provides a large heat shrinkage.

(Structure of the Invention) The present invention heat-sets a stretched film made of a thermoplastic resin at a temperature 100 to 180°C higher than the glass transition temperature (Tg) of the resin in a heat treatment zone of a tenter. Both ends of the heat-set film are cut and separated in a film-processing wind-free zone provided between the cooling zone and the heat-set film with both ends cut off is gradually cooled in the cooling zone and the take-up speed is reduced. This is a relaxation heat treatment method for a thermoplastic resin film, which is characterized in that the film is relaxed by deceleration, and then the film subjected to the relaxation heat treatment is cooled to room temperature and wound up.

Here, the glass transition temperature (Tg:° C.) is the glass transition temperature of an unstretched film of a thermoplastic resin. Usually, DSC
(differential scanning type thermal machining), for example, T (1) of polyethylene terephthalate is 69 to 70°C.

The first feature of the present invention is that the temperature of the tenter 'ISM<
A zone without film processing wind is provided between the heat-setting zone and the cooling zone, and both ends of the heat-setting film are cut and separated in the zone. This allows film circulation IM
Both ends of heat-setting film can be stably cut without being affected by wind. Moreover, since the film at the cutting position is relatively hot, it is possible to sufficiently relax the film in the longitudinal direction by slowing down the film take-up speed, and as a result, a low heat shrinkage rate can be imparted. Furthermore, there is an advantage that a difference can be created between the longitudinal heat shrinkage start temperature and the transverse heat shrinkage start temperature, thereby making it possible to control the heat shrinkage rate of the film in the transverse direction to some extent. The difference in the temperature at which thermal contraction begins in both axial directions is thought to be due to the following reasons.

The film traveling inside the tenter is held at both ends by clips, and both ends are clipped and then loosened by deceleration of the film take-up speed.The effect of this longitudinal relaxation is from the front of the cutting position, that is, from the heat. Since the thermal contraction in the fixed zone and in the yellow direction is completely parasitic by the clip, the thermal contraction starts from the cut position, and the thermal contraction rate (12r) is determined by the temperature at that cut position. It will be done.

Depending on the situation, the position of this collar can be either on the heat fixing zone side or on the cooling zone side.

The second feature is that the heat-set film with both ends cut off is gradually cooled to a predetermined temperature in a cooling zone, or in some cases even on a take-off roll system.The temperature at which both ends of the film are cut is relatively low. Due to the high temperature, vertical wrinkles occur when the material is rapidly cooled down in the subsequent cooling process. To prevent this, it is effective to slowly cool the film, and in order to cool the film in stages, the temperature of the cooling zone is controlled in stages, and rapid cooling due to contact with the rolls in the take-up system is prevented. Therefore, it is preferable to use a temperature control roll. It is preferable that the humidity of the cooling air in the cooling zone is at a temperature higher than T().
]～(Tg+80) ℃Furthermore, Tg～(T(J+60)
℃, especially 1 g to (Tg - + - 40) ℃, and until the film temperature becomes lower than 1 g, the humidity difference between the take-up roll and the film should be within 40 ℃. is preferable. One or more take-up rolls can be provided, but in the case of two or more take-up rolls, it is preferable that the temperature of the stand roll satisfies the above temperature conditions.

In addition, nip rolls are installed to prevent the film from slipping on the roll in order to ensure constant and reliable film relaxation, and to prevent the tension of the subsequent take-up system and film winding tension from reaching the tenter side. It is preferable.

In this case as well, the temperature of the nip roll is preferably the same as that of the take-up roll.

The film made of thermoplastic resin in the present invention is a film made of thermoplastic resin such as polyester, polyamide, polyolefin, etc. Among these, a film made of polyester, particularly polyethylene terephthalate, is preferred.

In addition, the stretched film may be a uniaxially stretched film stretched only in the vertical direction or only in the horizontal direction, or may be a biaxially stretched film stretched in the vertical direction and the horizontal direction. The fixed temperature is 100 to 180 °C from the glass transition temperature of the thermoplastic resin (T()>
It is. As the stretching method 1 conditions, etc., conventionally known methods or those accumulated in the art can be used.

Furthermore, the present invention will be explained based on the drawings.

FIG. 1 is a schematic cross-sectional view showing the main parts of a conventional device from a tenter to a take-up roll. The longitudinally stretched thermoplastic resin film 1 is preheated in a preheating zone 3 with its side edges held by clips of a tenter rail 2, and then laterally stretched in a stretching zone 4. After being heat-set in a heat treatment zone (heat-fixing zone) 5 and cooled in a cooling zone 6, it is taken up by a take-up roll 10.11 and then wound up by a winding facility (not shown).

FIG. 2 is a schematic sectional view showing the main parts from the tenter to the cooling roll to which the present invention is applied. The longitudinally stretched thermoplastic resin film 1 is preheated in a preheating zone 3 while its side ends are held by clips of a tenter rail 2, and then laterally stretched in a stretching zone 4. Subsequently, in heat treatment zone (heat setting zone) 5, the glass transition temperature (TCI) +10
0°C or above and below the glass transition temperature (Tg) + 180°C, cooled with cooling air at a temperature above the glass transition temperature (Tg) in cold fJ) zone 6, and in some cases gradually cooled in stages. Therefore, the cooling zone is divided into multiple sections (6'
, 6") L/te independent temperature (above the glass transition temperature,
6' zone temperature≧6'' zone temperature). At that time, zone 7 is provided with cutter equipment 8, 8' for cutting both ends of the film without substantially blowing out hot air. It is provided between the heat treatment zone 5 and the cooling zone 6.The cutter equipment 8, 8' separates both sides of the heat-set film by cutting.The film with both ends cut (
The central part) is slowly cooled in the cold N1 zone 6, and the temperature is adjusted to a temperature where the humidity difference with the film is within 40°C to avoid rapid cooling. By counting, cutter (8,8'
) and the rolls 10 while being relaxed.

In this case, if the temperature of the film is high and the film remains above the glass transition temperature even after passing through the take-off roll 10, it is preferable to further adjust the temperature of the take-off roll.

Furthermore, the film is held down in the width direction by the nip roll 9 in order to keep the take-up roll 10 and the film running speed constant and constant, and to prevent the tension of the subsequent take-up system and winding system from exerting on the film relaxation zone. The nip roll 9 may be positioned at the point when the temperature of the film becomes equal to or lower than the glass transition temperature. The film is then cooled to room temperature and rolled up.

(Example) The present invention will be explained below with reference to Examples.

Example 1 Polyethylene terephthalate (intrinsic viscosity determined using 0-chlorophenol solvent at a temperature of 35°C: 0.72) was formed into an unstretched film by a conventional method, and this was stretched 3° to 5 times in the machine direction. Then, in a device (tenter) shown in Fig. 2, the film was stretched 3.6 times in the transverse direction in the stretching zone 4, and then heat-set at 230°C in the heat treatment zone 5, using cutter equipment that does not blow out hot air. After cutting both sections of the heat-fixing film in zone 7 on the right, it was loosened by reducing the pulling speed by 1.5%, and gradually cooled in cooling zone 6 at 100 °C [1 embryo]. The temperature of the film leaving the cold FA zone was 80°C.
The slowly cooled film was taken up by a take-up roll 10 at a temperature of 65°C between nip rolls 9, cooled to room temperature, and wound up. The longitudinal heat shrinkage rate when held for minutes was 0.1%.

Moreover, the flatness of this film was good, with no wrinkles or b.

Comparative Example 1 A film of polyethylene terephthalate (intrinsic viscosity 0.72>) was formed and longitudinally stretched in the same manner as in Example 1.
After stretching 3.6 times in the 1 yellow direction using the equipment shown in the figure, 230
After heat setting at ℃, the film was taken off. Obtained thickness 10
When a 0 μm biaxially oriented film was held at 150° C. for 30 minutes, the heat shrinkage rate was 1.2%, which is a high value as a heat shrinkage rate.

(Effect of the invention) In the present invention, both ends of the stretched thermoplastic resin film are cut in a zone between the heat treatment (heat fixing) zone and the cooling zone where hot air is not blown out. It is possible to reduce the high heat shrinkage by 1q, and since the start position of heat shrinkage in the vertical direction is different (heat shrinkage in one direction starts upstream of the film from the cutting position),
It has the advantage of increasing heat shrinkage in the vertical direction and making the heat shrinkage characteristics in the horizontal direction close to those in the vertical direction to some extent, and also because hot air is not blown into this zone when cutting the film. It also has the advantage of stable film running and smooth film cudding.

By controlling the cooling air in the relaxation zone and avoiding rapid cooling on the take-up roll, it is effective in suppressing vertical wrinkles that occur in the film.

In addition, if the nip roll is used to keep the take-off C1-roll and film running speed constant and consistent, and to prevent the tension of the following take-up system and winding system from reaching the film relaxation zone, it is possible to further increase the heat in the longitudinal direction of the film. It has the advantage that the shrinkage 1Z1 property is stable and uniform.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing the main parts of a conventional device from a tenter to an auxiliary roll. FIG. 2 is a schematic sectional view showing the main parts from the tenter to the cooling roll to which the present invention is applied. 1: Thermoplastic resin film 2: Tenter rail, 3: Preheating zone. 4: Stretching zone, 5: Crystallization zone. 6: Cooling zone. 6', 6": Cold 1.0 zone divided into multiple parts. 7: Zone without film processing wind. ε3.8': Cutting blade, 9: Nip roll.

Claims (1)

[Claims] 1. A stretched film made of a thermoplastic resin is heated in a heat treatment zone of a tenter to a temperature of 100 to 18
Heat set at a temperature 0°C higher, cut and separate both ends of the heat set film in a film processing wind-free zone provided between the heat treatment zone and the cooling zone, and separate the heat set film with both ends cut off. A method for relaxing heat treatment of a thermoplastic resin film, which comprises gradually cooling the film in a cooling zone and relaxing it by slowing down the take-up speed, and then cooling the film subjected to the relaxation heat treatment to room temperature and winding it up. 2. The relaxation heat treatment method according to claim 1, characterized in that the temperature of the cooling air supplied to the cooling zone is set to be equal to or higher than the glass transition temperature of the thermoplastic resin. 3. The relaxed heat-treated film that has come out of the tenter is taken up using one or more take-up rolls whose temperature difference between the film and the film is adjusted to within 40°C until the temperature of the film becomes lower than the glass transition temperature of the thermoplastic resin. 2. The relaxation heat treatment method according to claim 1, wherein the relaxation heat treatment method is characterized in that the relaxation heat treatment method is carried out by taking the work. 4. The relaxation heat treatment method according to claim 3, characterized in that a nip roll is combined with the take-up roll.