JPH03216326A - Manufacture of thermoplastic resin film - Google Patents

Abstract

PURPOSE:To enable lateral stretching and thermal set whose physical properties are uniform by reducing a bowing phenomenon, by a method wherein at the time of manufacturing of a thermoplastic film which is stretched at least laterally, the film is cooled to a temperature not exceeding the glass transition temperature by providing a cooling process satisfying a specific formula between a lateral stretching process and thermal setting process. CONSTITUTION:At the time of performance of lateral stretching and setting treatment, a film prior to a thermal setting process is cooled to a temperature not exceeding the glass transition temperature and a bowing phenomenon generated with a lateral stretching process is reduced. The lower this cooling temperature is and the bigger a value of a ratio L/W between a length L of a cooling process and a film width W is, the more a reducing effect of the bowing phenomenon is improved, and it is preferable to select the length L of the cooling effect with a formula of L/W>=2.0. Furthermore, the formula of L/W>=3.0 is preferable. In the case where a tenter performing the lateral stretching process and thermal setting process is cut off, since a film is run within atmosphere, it is good that the film is cooled to a temperature not exceeding the glass transition temperature and satisfies L/W>=1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for uniformly producing a thermoplastic resin film. In detail, the production of a film that suppresses the bowing phenomenon that occurs when it is laterally stretched and heat-set using a tenter and has uniform physical, chemical, and physicochemical properties τ in the width direction h/1 ．． Regarding.

(Prior art) Thermoplastic resin films, especially films made of biuniaxially oriented polyester, polyamide, polyolefin, polyvinyl resin, polyphenylene sulfide, etc.
It is used for packaging, industrial use, and other uses, and it is desirable that the physical properties be the same across all parts of the film in the width direction.

However, with conventional manufacturing methods, it is extremely difficult to make the physical properties of the product film uniform in the width direction. The reason for this is that both ends of the film are held by clips in the tenter, and the longitudinal stretching stress generated by the stretching process and the shrinkage stress generated by the heat setting process are restrained by the clips, which are the gripping means. On the other hand, in the center of the film, the binding force is weaker due to the influence of the gripping means.
It has been found that the central portion of the film lags with respect to the end portion held by the clip due to the effect of the stress listed in L. When transverse stretching and heat setting are performed continuously in the same tenter, if a straight line is drawn along the width of the film before it enters the tenter, then this straight line can be drawn inside the tenter. The film deforms into a convex shape in the region at the beginning of the stretching process, returns to a straight line in the region immediately before the end of the stretching process, and deforms into a concave shape after the stretching process is completed. Furthermore, the concave deformation reaches its maximum value at the beginning of the heat-setting ball-sized region, and the curve remains unchanged as it passes through subsequent tenters, leaving a concave deformation in the film that leaves the tenter. This phenomenon is called the bowing phenomenon, and this bowing phenomenon causes the physical properties of the film to become non-uniform in the width direction.

Due to the bowing phenomenon, a main axis of orientation that is further inclined in the vertical direction with respect to the bowing line occurs in the side end portions of the film, and the angle of the main axis of orientation tends to differ in the width direction. As a result, physical property values such as longitudinal thermal contraction coefficient, thermal expansion coefficient, and wet expansion coefficient differ in the width direction of the film. Due to this bowing phenomenon, printing pinotchi may be rubbed in packaging applications such as printing lamination, bag making process, etc.
This causes problems such as spotting, curling, and meandering. Further, as an example of L-industrial applications, base films for fluoro- and pea-discs cause troubles such as poor magnetic recording characteristics due to internal anisotropy.

More specifically, as a conventional technique in which a cooling step is provided between the transverse stretching and heat setting, Japanese Patent Publication No. 35-11774 discloses a method in which a relaxation step at 20°C to 150°C is interposed between the transverse drawing and heat setting. A manufacturing method has been proposed that includes a cooling step. However, the length of this cooling process is not described at all, and the effect of reducing the bowing phenomenon is also completely unknown. Furthermore, as a technique for reducing or eliminating the bowing phenomenon, Japanese Patent Application Laid-Open No. 73978/1984 proposes a film manufacturing method in which a group of prowls is provided between the stretching and heat setting steps. However, in this technology, the temperature of the intermediate zone where the second film is installed is above the glass transition point, and the rigidity of the film at the second point is low, so the improvement effect is small. In addition, special public service 1986-2
Japanese Patent Application No. 4459 proposes a method of forcibly advancing only a narrow area near the center with nisoprol while gripping both ends of the film after completing lateral stretching.

However, with this technology, it is necessary to install the nip roll in a high-temperature area inside the tenter, and the roll and its peripheral equipment must be cooled.Also, since the film is at a high temperature, there is a risk of scratches caused by the roll, which is not practical. is restricted by. Furthermore, Japanese Patent Publication No. 62-43856 proposes a technique in which a film immediately after horizontal stretching is cooled to a temperature below the glass transition temperature, and then heat-set in multiple stages and simultaneously stretched in the horizontal direction. There is. However, with this technology, the bowing phenomenon is less likely to be reduced during the cooling process, or because the bowing phenomenon is likely to reoccur during heat setting, but in addition to the cooling ball process, a complex process of multi-stage heat setting and re-stretching is required. It becomes. Therefore, there is a concern that it may be difficult to stably control the ambient temperature and film temperature within the tenter over a long period of time. In addition, this proposal was also
Similar to Publication No. 74, there is no mention of the length of the cooling process. Historically, Japanese Unexamined Patent Publication No. 183327/1983 discloses that after longitudinal stretching, when transversely stretching and heat-setting with a tenter, only the side end portions are placed between the transverse stretching zone and the heat-setting zone at a temperature higher than the glass transition point. A technique has been proposed in which a heat zone having a temperature below the L heat fixation temperature is installed. However, with this technique, the temperature in the preheating zone must be controlled while creating a temperature gradient in the width direction, so there is a concern that it may be difficult to control the temperature of the film over a long period of time.

In addition, in the embodiment of the present proposal, since the length of this preheating zone is as short as half the film width, it is presumed that the effect of reducing the bowing phenomenon is small. Also, JP-A-1-16542
No. 3 proposes a technique in which a film after being laterally stretched is cooled to a temperature below the laterally stretching temperature, and then stretched again in the laterally direction while increasing the temperature in multiple stages. However, with this technology, the cooling F culm may be less effective in reducing the bowing phenomenon during the cooling process as in the case of Japanese Patent Publication No. 62-43856, or because bowing is likely to occur during the heat setting process. In addition to the process of heat setting in multiple stages, the process of stretching is complicated. Therefore, there is concern that it may be difficult to stably control the ambient temperature and film temperature within the tenter over a long period of time. Although this proposal states that the length of the cooling step is preferably 5 or more times the width of the film, it is not clear whether this is the basis for this. There is also a description that the cooling temperature is preferably higher than the glass transition point temperature and lower than the stretching temperature. However, if the cooling process is this long or if the temperature is below the cooling temperature or above the glass transition temperature, there is a concern that the effect of reducing the bowing phenomenon will be small, so a complicated process like the one described in L must be adopted. It is presumed that it was not. Also, Japanese Patent Publication No. 1-25694, Japanese Patent Publication No. 1-25696
The publication discloses that the film is laterally stretched by reversing the running direction of the film.
Techniques for heat fixation have been proposed. However, this technology requires the film to be reversed in order to reverse the running direction of the film.
·Day. It is necessary to wind it up, and there is a problem in that it is not limited by productivity, which is an offline manufacturing method.

(Problems to be Solved by the Invention) It is an object of the invention to provide a manufacturing method involving effective transverse stretching and heat setting that can solve this problem by χ·1, reduce the bowing phenomenon, and obtain a film with uniform physical properties. It is in.

(Means for Solving the Problems) The present inventors observed changes in the bowing line inside the tenter, clarified the process of occurrence of the bowing phenomenon through various studies, and studied means to reduce the bowing phenomenon. We have arrived at the present invention.

In the present invention, when producing a thermoplastic resin film stretched at least in the transverse direction, a cooling process satisfying the following formula is provided between the transverse stretching process and the heat setting process to cool the film to a temperature equal to or higher than the glass transition temperature. This is a method for producing a thermoplastic resin film characterized by the following.

L/W≧1.0 In the -L formula, L is the length of the cooling process (m),
W means film width (m). Here, the length of the cooling process is the length from the point where the temperature is substantially lower than that of the previous ball in the cooling process to the longest point where the temperature of the next process is substantially higher than the temperature of the cooling process. , and the film width W means the distance between the tenter chrysops at the tenter output 11. In addition, here, the lateral direction means a direction perpendicular to the running direction of the film, and the longitudinal direction means the running direction. That is, when the cooling temperature is lower than the stretching temperature, the glass transition point 7
In the case of L of M degrees or more, the bowing strain is improved to some extent, but the improvement in the practical physical property difference in the width direction is not fully satisfactory, but the physical property difference is practically satisfactory below the glass transition point temperature. I discovered something.

The present invention will now be described in detail.

In the present invention, a thermoplastic resin is heated and melted to a temperature of 1-10% higher than its melting point, extruded into a film form from an extrusion means including a suri-no-to die onto the surface of a cooling drum, and then longitudinally moved by a group of rolls with different roll speeds. It is known that the film is stretched, transversely stretched with a tenter, heat-set if necessary, and wound up with a film winder or the like. In the present invention, the film forming/stretching conditions include such resin melting/extrusion conditions, casting conditions, longitudinal force direction stretching conditions, and horizontal force direction stretching conditions.
Directional stretching conditions, heat setting conditions, rolling conditions, etc. can be selected as appropriate.

Thermal IJJ plastic resins applicable to the present invention include 4, polyethylene terephthalate, and polyethylene. Polyester resins such as 6-naphthalate, polyethylene isophthalate, and polybutylene terephthalate; polyamide resins such as nylon-6 and nylon-66; polyolefin resins such as polypropylene and polyethylene;
Examples include polyphenylene sulfide, polyether sulfone, polysulfone, polyether ether ketone, polyether ketone ketone, polyethylene trimellited imide, and many other simple substances, copolymers, mixtures, and composites.

In the present invention, when a thermoplastic resin film is laterally stretched and heat-set, the film before the heat-setting step is cooled to a temperature below the glass transition point, thereby reducing the bowing phenomenon that occurs during the lateral stretching step. The lower this cooling temperature is, the more effective it is in reducing the bowing phenomenon. The larger the value of the ratio L/W between the length of the cooling process and the film width W, the better the effect of reducing the bowing phenomenon. It is preferable to select a length of .0 equal to the length of a cooling ball. More preferably, L/
W≧3.0.

In addition, when cutting out the tenter that performs the transverse stretching process and the heat setting process, the film is cooled to below the glass transition temperature in order to run in the atmosphere, and the length of the cooling process and the film width W are The present invention also includes performing the transverse stretching step and the heat setting step in separate tenters as long as the ratio L/W≧1.0 is satisfied.

Furthermore, in the cooling step after this cooling step and the heat setting step, it is preferable to pass the film through a speed-controllable dinoprole group, and the effect is significantly improved. The material of this nibro roll is a combination of a metal mirror surface and a rubber elastic body, and the nibro roll tensions the film at a speed relative to the tenter's clip, so the speed must be easily controlled. It is also preferable that nisoprol be used alone or both together to control their effects.

The present invention naturally includes cases in which the transverse stretching, cooling, and heat setting steps are continuous, and cases in which at least one step in the re-stretching, relaxing, and constant length step is included between the steps. Furthermore, stretching force methods other than the manufacturing force method in which longitudinal stretching is followed by transverse stretching are also included in the present invention. For example, a stretching method in which longitudinal stretching is performed after horizontal stretching, a stretching method in which longitudinal stretching is performed again after longitudinal and lateral stretching, a stretching method including longitudinal two-stage stretching, and a stretching method in which both ends of the film are trimmed after horizontal stretching and longitudinal stretching are carried out. It is not limited to the above unless it exceeds.

The reason why good effects can be obtained in the present invention is as follows.
In determining the length of the cooling process necessary to reduce the bowing phenomenon, we set up a mathematical model that could apply the finite element method, which no one had been able to do, and made it possible to estimate the propagation of stretching stress through numerical analysis. As a result, when the ratio of the length of the cooling process to the film width W is L/W=1.0, the stress propagation becomes about the same, and when L/W=2.0, the stress propagation becomes about 17lO, and L/W=1.0. This is because we found from calculated values that W = 3.0 is completely zero, confirmed it with an actual machine, and found that it can be applied in any case.

Next, examples will be shown.

(Example) FIG. 1 shows an example of an apparatus used in the present invention. The hot plastic resin extruded from the T-die 1 is rapidly cooled by a chill roll 2 and formed into a film.

The film is stretched in the machine direction by roll M stretching machines 3 and 3', and then passes through a heating zone 6 and enters a transverse stretching zone 7 while being held at both ends by clips 5 (not shown) of a tenter 4. Stretched laterally. Further, the film enters a cooling zone 8, passes through heat setting zones 9 and 10, is removed from the clips 5 after being heat set, exits the tenter, and is wound up by a winder 11.

In the present invention, bowing distortion is caused by drawing a straight line on the surface of the film before it enters the tenter, and deforming the final film L into an arched shape as shown in Figure 2. The situation was calculated as follows: B=b/WX 100 (%) where B=Boeing distortion (%) W=Finolem width (m) b=Maximum concavity of Boeing line (■■).

Furthermore, in the present invention, the measurement of the physical properties of the film after the completion of the film forming process is as shown below. Note that the measurement points were the center and edges of the film.

(1) Fart breakage rate It was measured using an Asobe refractometer.

■ Heat shrinkage rate: 105, 15 for polyethylene terephthalate
0.30 minutes at 200°C, in the case of nylon = 6,
It was calculated from the amount of shrinkage when held at 95°C and 160°C for 10 minutes.

(3) Boiling water shrinkage rate (nylon-6 only) Samples marked with marked lines as shown in Fig.
After conditioning for 2 hours at 50% RH), measure the distance between each gauge line. shall be. Next, heat treatment is performed in boiling water at 10'0°C for 30 minutes. After this treatment, zoning was performed for 30 minutes under standard conditions, and the distance between each gauge line was measured. shall be. From this result, the boiling water shrinkage rate was calculated using the following formula.

In addition, the measurement direction of the film physical property values of (l) to (3) is as follows:
-45° direction with respect to the vertical direction (hereinafter referred to as the a direction)
, +45° direction with respect to the vertical direction (hereinafter referred to as b direction)
There are two directions. In addition, clockwise to the vertical direction is plus (+), and counterclockwise to the vertical direction is minus (1).
direction.

Here, regarding the physical property values (I) to (3), calculate the ratio of the absolute values of the physical property values in both the av and b directions at the edge of the film, and the closer the value is to 1.0, the greater the value in the width direction of the film. Assume that the difference in physical properties is small.

The effect of the present invention is that the bowing distortion is small (11~
In the case of polyethylene terephthalate, in the case of polyethylene terephthalate, the ratio of the absolute values of the thermal shrinkage rate in both the at and b directions at 105°C is 0.0. 8 or more, and in the case of nylon-6, the ratio of the absolute values of the boiling water shrinkage ratio in both ASB directions was 0.5 or more and 7 was used as the criterion.

This will be explained below with some examples.

Example 1 Polyethylene terephthalate resin was melted and extruded through a T-die, formed into a film on a chill roll, and then stretched 3.6 times in the machine direction with a roll stretching machine, and then stretched 3.7 times in the cross direction with a tenter. , a heat-set biaxially oriented polyethylene terephthalate foot film. The temperature in the tenter was such that the preheating temperature was 90°C, the stretching temperature was 100°C, the subsequent cooling temperature was 40°C, and the heat setting temperature was 220°C. The film was then wound in the usual manner. In addition, the length of the cooling zone and the film width W
The ratio L/W was set to 1.0.

Example 2 In Example 1, the length of the cooling zone and the film width W
A two-wheel oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the ratio L/W was 2.0.

Example 3 In Example 1, the length of the cooling zone and the film width W
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the ratio L/W was 3.0.

Example 4 A two-wheel oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the temperature of the cooling zone was 65°C.

Comparative Example 1 A two-wheel oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the cooling step was not performed.

Comparative Example 2 A biaxially oriented polymer/terephthalate film was produced in the same manner as in Example 1 except that the temperature of the cooling zone was set to 0°C.

Comparative Example 3 A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 2 except that the temperature of the cooling zone was 100°C.

Example 5 Nylo/-6 resin was melted and extruded through a T-die, formed into a film using a chill roller, stretched 3.25 times in the longitudinal direction using a roll stretching machine, and then stretched 3.5 times in the transverse direction using a tenter. A heat-set biaxially oriented nylon-6 film was obtained.

The temperature in the tenter was such that the preheating temperature was 60°C, the stretching temperature was 85°C, the subsequent cooling temperature was 40°C, and the heat setting temperature was 235°C. The film was then wound in the usual manner. In addition, the length L of the cooling zone and the film width W
The ratio L/W was set to 1.0.

Example 6 In Example 5, the length of the cooling zone and the film width W
A biaxially oriented nylon-6 film was obtained in the same manner as in Example 5 except that the ratio L/W was 2.0.

Example 7 In Example 5, the length of the cooling zone and the film width W
A biaxially oriented nylon-6 film was obtained in the same manner as in Example 5 except that the ratio L/W was 3.0.

Comparative Example 4 A biaxially oriented nylon 10 film was obtained in the same manner as in Example 5 except that the cooling step was not performed.

Comparative Example 5 A biaxially oriented nylon-6 film was obtained in the same manner as in Example 5 except that the temperature of the cooling zone was 100°C.

Comparative Example 6 A biaxially oriented nylon-6 film was obtained in the same manner as in Example 7 except that the temperature of the cooling zone was changed to 100°C.

Table 1 shows the film forming conditions, bowing strain, and film physical property values in Examples and Comparative Examples.

(Efficacy of the invention!i) Comparative examples (cases where no cooling is performed, or even if a cooling process is included, the cooling temperature is below the glass transition point temperature) have bowing distortion and a film that is not sufficiently satisfactory for practical purposes. Differences in physical properties occur, but in the examples of the present invention, the bowing phenomenon that occurs during the process of transversely stretching and heat setting a thermal 1J plastic film is suppressed, and the physical properties are uniform in the width direction of the film to a degree that is sufficiently satisfactory for practical use. It can be seen that a film having the following properties can be produced.

[Brief explanation of drawings]

The figure shows marked lines for measuring boiling water shrinkage. In the figure, 1 is a T-die, 2 is a chill roll, 3 and 3' are roll stretching machines, 4 is a tenter, 5 is a tenter clip, 6
is F heat sawn, 7 is lateral stretching zone, 8 is cooling noon, 9
10 and 10 indicate a heat fixing zone, and 11 and 11 indicate a winding machine, respectively.

Claims (1)

[Claims] When producing a thermoplastic resin film stretched at least in the transverse direction, a cooling process satisfying the following formula is provided between the transverse stretching process and the heat setting process to reduce the temperature to below the glass transition point. A method for producing a thermoplastic resin film characterized by cooling. L/W≧1.0 In the above formula, L means the length of the cooling process (m), and W means the film width (m).