JPH04270631A - Heat treatment of thermoplastic film - Google Patents

Abstract

PURPOSE:To obtain a film having stability by uniformizing the physical properties in the lateral direction of the film. CONSTITUTION:In the heat treatment of a thermoplastic film in such a state that the end parts of said film are grasped, when the max. temps. of the heat shrinkage stress of the end parts and central part of the film in the longitudinal direction thereof are respectively set to TE and TC( deg.C), the film to be heat- treated satisfies 30>TC-TE>=0.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for heat treating a thermoplastic film, and more specifically, a method for producing a film with uniform physical properties in the width direction, and a method for heat treating a film with excellent thermal dimensional stability. It is related to.

0002

[Prior Art] As a method for manufacturing a film having uniform physical properties in the width direction, as typified by, for example, Japanese Patent Application Laid-Open No. 1-150521, there is a stepwise temperature increase in which horizontal stretching and heat treatment are successively carried out to raise the temperature. Lateral stretching/heat treatment method, JP-A-59-11
4028 and the like, a method has been proposed in which a heat-treated film is wound up and then passed through a tenter in the opposite direction again. In addition, in order to achieve thermal dimensional stability, for example, as typified by Japanese Patent Application Laid-open No. 62-101,421, methods of aging the product roll as it is for a long time or offline heat treatment are used. It was getting worse.

0003

[Problems to be Solved by the Invention] However, the conventional heat treatment method described above has the following problems.

(1) The stepwise heating heat treatment method not only has a small effect of improving uniformity in the width direction, but also has drawbacks such as an increase in heat shrinkage and a significant change in film quality. Was.

(2) Off-line processing methods and roll aging methods certainly improve thermal dimensional stability, but have drawbacks such as poor flatness and winding appearance, and increased manufacturing costs.

The present invention aims to solve these problems and provide a heat treatment method that provides uniform physical properties in the width direction and excellent thermal dimensional stability.

[0007]

[Means for Solving the Problems] The present invention provides a film with specific characteristics and/or a heat-treated film.
Alternatively, this can be achieved by subjecting the edges of the film to specific heat treatment conditions.

That is, in a method of heat-treating a thermoplastic film by gripping the edges, the film to be heat-treated has a maximum temperature T of heat shrinkage stress in the longitudinal direction of the edges of the film.
Heat treatment of a thermoplastic film characterized by satisfying 30>TC -TE ≧0 (°C), where E (°C) and the maximum temperature of heat shrinkage stress in the longitudinal direction at the center of the film are TC (°C). In the above-mentioned heat treatment method for a thermoplastic film, the film to be heat treated has a heat shrinkage stress in the longitudinal direction of the polymer (E constituting the film end portion) of FE (kg/
mm2), polymer (C) constituting the central part of the film
The present invention relates to a method for heat treatment of a thermoplastic film characterized by satisfying FE /FC ≧1.5 at a temperature of TE or higher, where FC (kg/mm2) is the heat shrinkage stress in the longitudinal direction of the film.

The thermoplastic polymer constituting the thermoplastic film of the present invention exhibits softening and fluidity when heated, and typical examples include polyethylene terephthalate, polybutylene terephthalate, polycyclohexanedimethanol terephthalate, and polyethylene naphthalate. or polyesters including copolymers thereof, nylon 6, nylon 66, nylon 610, nylon 11
, polyamides including nylon 12, polymethaxylylenediamine adipamide, or copolymers thereof, polyolefins including polypropylene, polystyrene, polymethylpentene, polyethylene or copolymers thereof, etc. It is something that Particularly in the case of the present invention, polyesters and polyamides are particularly preferred. Among them, polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6 naphthalate and nylon 6 are particularly effective in the present invention.

Of course, the thermoplastic resin used in the present invention contains known additives for polymers, such as thickeners, thinners, nucleating agents, antistatic agents, stabilizers, lubricants, and antiblocking agents. , pigment dyes, ultraviolet absorbers, etc. may be added within a range that does not adversely affect quality.

Next, the edges of the film to be heat treated are
It must have specific characteristics. In other words, the maximum temperature TE (°C) of the heat shrinkage stress in the longitudinal direction at the edges of the film to be heat-treated is the same as the maximum temperature Tc (°C) of the heat shrinkage stress in the longitudinal direction at the center, or at least 30°C. It is necessary that the temperature is lower than 20°C, preferably lower than 20°C, and more preferably lower than 10°C. If the maximum temperature difference ΔT (=TC - TE) of this heat shrinkage stress is a negative value or 30°C or more, not only will it not be possible to obtain a film with completely uniform physical properties in the width direction, which is the objective of the present invention. This is because a film with excellent thermal dimensional stability cannot be obtained. The parameter indicating the uniformity of physical properties in the width direction is the distribution of the degree of orientation of the main axis in the width direction, and the measurement angle is compared with the measurement angle at a point 1 m apart in the width direction. When the difference is within 5 degrees, preferably within 3 degrees, it is determined that the physical properties in the width direction are uniform. In addition, parameters indicating thermal dimensional stability include a dry heat shrinkage rate of less than 0.1% after 30 minutes at 150°C measured in the longitudinal direction;
Preferably, when it is less than 0.03%, it is said that the thermal dimensional stability is excellent.

Further, the longitudinal heat shrinkage stress FE (kg/mm2) of the film end portion (E) is equal to the longitudinal heat shrinkage stress FC (kg/m2) of the center portion (C) at a temperature higher than TE.
By performing heat treatment using a film whose height is 1.5 times or more, preferably 2 times or more, more preferably 3 times or more, the height of m2), heat treatment that meets the purpose of the present invention can be achieved. This heat shrinkage stress ratio (FE/FC) is 1.5
This is because if it is less than 2, preferably less than 2, a film with uniform physical properties in the width direction and excellent thermal dimensional stability cannot be obtained. This relationship applies not only to temperatures near TE or higher;
Heat treatment temperatures must be applied up to near the melting point of the thermoplastic film.

Next, a method for obtaining the film of the present invention will be described below.

[0014] A film having the above-mentioned properties has, for example, different polymers (C) in the center and edges of the film.
and (E), can be obtained by combining them in the width direction and optimizing the film forming conditions.

Particularly preferred polymers (E) are highly crystalline and high melting point polymers, such as polybutylene terephthalate and derivatives thereof.

Polymer (C) and polymer (E
), polymers (C) and (E) are combined in the mouthpiece (from the conduit that supplies the molten resin to the slit-like mouth surface from which the resin is discharged), and the polymers (C) and (E) are combined in the mouthpiece. In other words, it refers to laminating part or all of the polymer (E) on both ends of the polymer (C). Note that it is preferable to use a composite material inside the cap because there will be no problem with adhesive strength. In addition, when laminating outside the die, any process may be performed as long as it is a process before lateral stretching.

One embodiment of manufacturing the composite film of the present invention will be explained based on the drawings.

FIG. 1 is a partially sectional front view of a composite film forming apparatus used in the present invention, and FIG. 2 is a side view of FIG. 1.

In FIGS. 1 and 2, 1 is a polymer (C)
2 is a polymer pipe for supplying polymer (E), 3 is a base, 4 is a casting drum, 5 is a polymer (C), 6 is a polymer (E),
7 is a composite film consisting of polymers (C) and (E).

Polymer (C) and polymer (E) are separately melted and supplied by two extruders (not shown), extruded through pipes 1 and 2 from a mouthpiece 3, and placed on a casting drum 4. The composite film 7 is obtained by cooling and solidifying. The polymer pipes 1 and 2 in the center and both edges may be separate as described above, or they may be integrated and only the polymer supply port may be changed as appropriate. Alternatively, a device may be used that directly supplies both polymers to the base.

The composite film 7 thus obtained is stretched in the longitudinal direction and the width direction. At this time, the TE temperature can also be changed depending on the film forming conditions, and can be shifted to a higher temperature side by increasing the longitudinal stretching temperature or by heat-treating the ends after longitudinal stretching. Further, the heat shrinkage stress FE at the end portions can also be increased to a large value by lowering the stretching temperature in the longitudinal direction or cooling the end portions during stretching.

[0022] The gripping part of the apparatus applied to the present invention includes all gripping devices used for lateral stretching of the film, and refers to, for example, a clip-shaped gripping device. Therefore, the width of the polymer (E) gripped by the gripping part needs to be at least the width along the TD gripped by the clip when stretched in the width direction (TD), that is, at least about 5 to 50 mm inward from both edges. It is. There is no problem with the effect even if it is 50 mm or more, but since the insulation part increases when cutting both edges of the film after TD stretching, it is not practical to use 150 mm or more.
~200 mm or less is preferable.

[0023] Furthermore, the effects of the present invention can be obtained by lowering the temperature at the edge of the film at the start of heat treatment after stretching in the width direction, lower than the temperature at the center of the film, preferably by 20°C or more, more preferably by 30°C or more. It becomes even more noticeable. The specific method of lowering the temperature at the end in this way is as follows:
This can be achieved by blocking the hot air at the edges of the film, or by sucking and exhausting the air at the edges.

[0024] In order to determine the maximum temperature of heat shrinkage stress and heat shrinkage stress, the measurement film is 10 mm wide and 20 mm long.
0 mm, and this sample is attached to a strain gauge measuring device with a clip spacing of 100 mm set in a hot air oven. The sample is heated with hot air at a rate of 2° C./min, and the thermal shrinkage stress caused by thermal contraction of the sample is recorded. As the maximum temperature of heat shrinkage stress, the temperature at which this shrinkage stress is maximum is adopted.

[0025] The film edge refers to the thick part of the film within 200 mm in the width direction from the film edge.

[0026]

EXAMPLES In order to make it easier to understand the effects of the present invention, examples will be described below.

Example 1 Polyethylene terephthalate PE as polymer (C)
T (intrinsic viscosity [η]=0.65, containing 0.5% by weight of silicon dioxide with an average particle size of 1 μm as an additive) and polybutylene terephthalate PBT (intrinsic viscosity [η]=0. 95) was used. After vacuum-drying each raw material at 180°C, they are melted and extruded separately using two extruders, and the width is adjusted according to the method shown in Figure 1 so that the center of the film is made of polyethylene terephthalate and both ends of the film are made of polybutylene terephthalate. E/C/E in direction
A laminated film (total width 750 mm) was obtained by casting using a conventional electrostatic application method. The width of one end PBT at this time was 100 mm.

[0028] This cast film was fed to a regular roll-type longitudinal stretching machine, and after being stretched 2.2 times at 105°C, and further stretched 2.5 times at 80°C, for a total of 5.5 times, only the edge portions were stretched. Crystallize by heating at 125℃ with air, then crystallize in the width direction at 120℃ in a clip-on tenter.
．． After stretching 0 times and cooling to below 70°C,
After heat treatment was performed for 9 seconds with 5% relaxation in a tenter heated to 130°C, intermediate heat treatment was performed for 3 seconds after cooling to 130°C. There was no film tearing and stable film formation was possible. At this time, for 3 seconds, which corresponds to the first 1/3 of the heat treatment process, hot air shielding plates are installed above and below the clip, and a suction duct is installed near the shielding plates to exhaust the air so that the temperature of the film in the center is lower than that of the film. The edge temperature was 35°C lower. Furthermore, the temperature TE at which the longitudinal heat shrinkage stress at the end of the unheated film after biaxial stretching is maximum is 100°C, and the value at that time is 3.2 kg/mm2, 20
The heat shrinkage stress at 0°C is 0.9 kg/mm2, and the temperature TC at which the heat shrinkage stress in the central longitudinal direction is maximum is 10
The heat shrinkage stress was 0.5 kg/mm2 at 5°C and 0.3 kg/mm2 at 200°C.

Table 1 summarizes the quality of the 75 μm thick film thus obtained.

[0030]

[Table 1]

Comparative Example 1 Completely the same as Example 1, except that polybutylene terephthalate as the end polymer (E) used in Example 1 was not used, and the same polyethylene terephthalate as the central polymer (C) was used for the ends. Biaxial stretching heat treatment was performed. Obtained 1
The heat shrinkage rate in the longitudinal direction/width direction at 50°C is 0.8%/0.
It is as high as 1%, and has a large orientation distribution in the width direction.
The deviation of the alignment axis at 1 m intervals was as much as 15°. When this film was heated to 150° C., the film meandered and did not run stably. In addition, the TC of the film before heat treatment is 105℃, TE is 70℃, F
C is 0.4kg/mm2, FE is 0.6kg/m
It was m2.

Comparative Example 2 Biaxial stretching and heat treatment were carried out in the same manner as in Example 1, except that high molecular weight polyethylene terephthalate with an intrinsic viscosity [η] = 0.8 was used instead of the polybutylene terephthalate used in Example 1. Did. Similar to Comparative Example 1, the thermal shrinkage rate at 150° C. in the longitudinal direction/width direction was as high as 0.7/0.2 (%), and the physical properties in the width direction were also nonuniform.

[0033] At this time, the temperature at which the heat shrinkage stress at the end before heat treatment reaches its maximum is TE115°C, and is 0.9 kg/mm2.
and that in the center (TC) is 0.6k at 105℃
g/mm2.

Example 2 The polymer (C) was nylon 6 (relative viscosity ηr3.
4, Amiran CM1021, manufactured by Toray) 90% by weight, and 5
-Polyethylene terephthalate copolymerized with 15% by weight of sodium sulfoisophthalic acid (intrinsic viscosity [η] 0.8)
A 10% by weight blend was used. The above nylon 6 was used as the polymer (E). This polymer was laminated using the same die composite device as in Example 1 to obtain a cast film. Subsequently, in the same manner as in Example 1, it was heated at 50°C for 3.3
After stretching, only the edge part was heat treated at 100℃, and then stretched 3.5 times in the width direction at 96℃ in a tenter.
Heat treatment was performed at 5° C. for 5 seconds while relaxing 3% in the width direction.

[0035] The temperature TE at which the heat shrinkage stress at the end of the unheated film after biaxial stretching is the maximum is 3 at 95°C.
．． 5 kg/mm2, and the temperature TC at which the heat shrinkage stress in the central portion was maximum was 2.0 kg/mm2 at 100°C.

[0036] Almost no orientation distribution in the width direction of the thus obtained 15 μm film was observed, and the film was uniform in the width direction.

[0037]

[Effects of the Invention] By employing the manufacturing method of the present invention, the following excellent effects can be obtained.

(1) The physical properties of the film in the width direction become uniform, and the so-called bowing phenomenon is significantly reduced or eliminated.

(2) The thermal dimensional stability of the film is increased,
In particular, the thermal shrinkage rate in the longitudinal direction is reduced, resulting in a thermally stable film.

(3) Neckdown in the width direction during stretching in the longitudinal direction is reduced, resulting in not only a film with stable quality but also increased stability in stretching.

(4) The stability of stretching in the width direction is improved,
Yield is improved.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view showing an example of a composite film forming apparatus used in the present invention.

FIG. 2 is a side view of the device of FIG. 1;

[Explanation of symbols]

1: Polymer piping 2: Polymer piping 3: Base 4: Casting drum 5: Polymer (C) 6: Polymer (E) 7: Composite film

Claims (6)

[Claims] Claim 1. In a method of heat-treating a thermoplastic film by gripping the edges, the film to be heat-treated has a maximum temperature of heat shrinkage stress in the longitudinal direction of the edges of the film TE (
30>TC-TE≧0(°C), where TC (°C) is the maximum temperature of heat shrinkage stress in the longitudinal direction at the center of the film. 2. The film to be heat treated has a heat absorption stress in the longitudinal direction of the polymer (E) constituting the end portion of the film.
E (kg/mm2), the heat absorption stress in the longitudinal direction of the polymer (C) constituting the central part of the film is FC (kg/m2).
2. The method for heat treating a thermoplastic film according to claim 1, wherein FE/FC≧1.5 is satisfied at a temperature equal to or higher than TE. 3. The method for heat-treating a thermoplastic film according to claim 1, wherein the temperature at the edges of the film during heat treatment is lower than the temperature at the center. 4. Claims 1 to 3, characterized in that the temperature at the edge of the film at the start of heat treatment is lower than the temperature at the center by blocking and/or suctioning and exhausting the hot air at the edge of the film. The method for heat treatment of a thermoplastic film according to any one of the above. 5. The method for heat treating a thermoplastic film according to claim 1, wherein the polymer constituting the thermoplastic film is at least one selected from polyester and polyamide. [Claim 6] The polymer constituting the edge of the film is
6. The method for heat treating a thermoplastic film according to claim 5, wherein the thermoplastic film is mainly composed of polybutylene terephthalate and a copolymer thereof.