JP2001105490A - Method for manufacturing thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a thermoplastic resin film for obtaining with good productivity the thermoplastic resin film of superior thermal dimension stability, plane properties and uniformity in the width direction. SOLUTION: Respective treatments of the lateral orientation, heat fixation and heat limpness are applied on a traveling oriented thermoplastic resin film to manufacture a biaxially oriented thermoplastic resin film, and the treatments are applied in the order of the lateral orientation, heat relaxation and heat fixation in a thermoplastic resin film manufacturing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic resin film.

More specifically, the present invention relates to a method for producing a thermoplastic resin for obtaining a thermoplastic resin film having excellent thermal dimensional stability, flatness, and uniformity in a width direction.

[0003]

2. Description of the Related Art A thermoplastic resin film has a physical property.
It is used in various fields depending on its thermal properties. In particular, polyester films are more preferably used because of their excellent mechanical properties and the like. Among them, polyester films, especially polyethylene terephthalate and polyethylene-2,6-naphthalate films are excellent in mechanical properties, thermal properties, and electrical properties.
It is used in various applications such as OA applications such as card applications, overhead projector (OHP) sheets and drafting base paper used in copiers and printers, and electrical insulating materials in motors and transformers.

[0004] Here, a polyester film is one in which mechanical properties such as Young's modulus are improved by molecular orientation by stretching, but in this film, distortion due to stretching remains in the molecular chain. Heating releases the strain of this molecular chain and has the property of shrinking. Utilizing this shrinkage property, it has been developed into shrink films for packaging and the like, but in general, in the above-mentioned applications, this shrinkage property often becomes an obstacle, and a film having excellent thermal dimensional stability. Is required.

[0005] Therefore, a method is generally used in which the heat setting is performed after the transverse stretching in the stenter to release the strain of the molecular chains. Although the amount of heat shrinkage decreases in accordance with the temperature of the heat setting, distortion cannot be completely removed only by the heat setting, and there is a problem that the heat shrinkage remains.

Conventionally, in order to remove the residual distortion, the width of the rail of the stenter is tapered (referred to as toe-in, relax, etc.) and slightly contracted in the width direction to completely remove the residual distortion. The method is adopted. However, in this method, the heat shrinkage in the width direction can be removed, but the heat shrinkage in the longitudinal direction cannot be completely removed. For this reason, various methods for removing the thermal shrinkage in the longitudinal direction have been studied in the past.

[0007] For example, Japanese Patent Publication No. 4-28218 proposes a method of performing a relaxation process in the longitudinal direction by gradually reducing a clip interval of a stenter. However, in this method, there is an upper limit to the relaxation rate due to a problem in the device, and when the relaxation rate is increased, the clip interval before the relaxation process is widened, and the unevenness in the physical properties of the clip gripping portion and the non-grip portion increases. Problems arise.

[0008] It is important to make the physical properties uniform in the width direction of the film to be manufactured in order to improve the yield. In general, unevenness in the physical properties in the width direction is caused by heat shrinkage stress generated during heating in the stenter and longitudinal shrinkage force generated in the transverse stretching step in the stenter, which causes heat in the heat treatment chamber to cause the longitudinal direction of the film having low rigidity to decrease. It is considered that the center of the film, which is weakly restricted, is caused by being drawn into the transverse stretching step. In addition, the unevenness in physical properties generated in this manner shows a distribution in the film width direction, similar to the bowing phenomenon in which a straight line drawn in the lateral direction of the film at the entrance of the stenter is curved in an arc at the exit.

Therefore, as a method of suppressing the bowing phenomenon, for example, a uniaxially stretched film is horizontally stretched by a stenter, the clip is once released, and the film is again gripped by the clip to obtain a temperature range of 120 to 240 ° C. Heat fixing while raising the temperature in (for example,
JP-A-57-87331), after pre-heating an unstretched film at a stretching temperature or higher, and simultaneously biaxially stretching in the machine and transverse directions,
Then, a method has been proposed in which the temperature is divided and raised in multiple stages at equal temperatures and reheated (for example, JP-A-54-137076).

[0010] However, even though such a method can suppress the bowing phenomenon to some extent, it is necessary to make various physical properties in the film width direction uniform without impairing thermal dimensional stability, mechanical properties, flatness, and the like. Not enough,
There is a problem that the device becomes large.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a thermoplastic resin film for obtaining a thermoplastic resin film having thermal dimensional stability, flatness and uniformity in the width direction. I do.

[0012]

Means for Solving the Problems The present invention has been accomplished as a result of intensive studies in consideration of the above-mentioned problems. A method for producing a thermoplastic resin film by performing each treatment of relaxation, which is a method for producing a thermoplastic resin film, wherein the treatment is performed in the order of transverse stretching, thermal relaxation, and heat fixing.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing a thermoplastic resin film by subjecting a running longitudinally stretched thermoplastic resin film to transverse stretching, heat fixing, and heat relaxation. The method comprises transverse stretching, heat relaxation, and heat setting. It is necessary to perform the processing in order.

By processing in this order, a film having thermal dimensional stability, flatness, and uniformity in the width direction can be obtained.

On the other hand, in a conventional general film forming method, the processing is performed in the order of transverse stretching, heat setting, and thermal relaxation. That is, in a general film forming method in which heat setting is performed after transverse stretching, a film immediately after transverse stretching has a very large heat shrinkage stress. Dimensional stability deteriorates. If the heat treatment temperature is increased to solve this problem, the uniformity in the width direction will be impaired, and it is difficult to achieve both of these characteristics by a general film forming method.

On the other hand, the present inventors have reduced the heat shrinkage stress of the film in the thermal relaxation after the transverse stretching, and then perform the heat treatment, so that the heat distortion remaining in the film is reduced. They have found that both thermal dimensional stability and widthwise uniformity can be achieved.

In the present invention, the thermal relaxation is a step of relaxing the film in the longitudinal direction and / or the width direction. In a non-contact state in which the film is floated, the running tension is reduced without restraining the film in the width direction. It is preferable to perform the treatment at 15 to 1.5 MPa for 1 to 90 seconds from the viewpoint of thermal dimensional stability and film formability. The running tension is more preferably from 0.2 to 1 MPa. The processing time is more preferably 2 to 60 seconds.

In the present invention, it is preferable to further perform a heat treatment after the transverse stretching and before the thermal relaxation in order to improve the flatness. The heat treatment is preferably performed at a temperature equal to or higher than the transverse stretching temperature and equal to or lower than the melting point of the film while the width direction of the film is restricted.

Further, in the present invention, it is preferable from the viewpoint of the uniformity in the width direction that both sides of the film are cut and separated immediately before the thermal relaxation and thermally relaxed. Unless both ends are cut and separated, the film thickness and the orientation of the film are different between the end and the central part of the film, so that heat is not uniformly relaxed in the width direction and the uniformity of physical properties in the width direction deteriorates. Resulting in.

In the present invention, the edge of the film means the periphery of the portion that is gripped by the clip when the film is stretched laterally by the stenter, and is generally 10 times smaller than the film thickness at the center of the film. % Indicates a thicker portion.

In the present invention, the heat setting treatment is a step of applying heat to the film while restraining in the width direction after the heat relaxation treatment. Preferably, the transverse stretching and the heat fixing are performed by separate stenters. In addition, the processing temperature of the heat setting processing is
It is preferable from the viewpoint of dimensional stability that the temperature is higher than the processing temperature of the thermal relaxation processing.

In the present invention, examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene and polymethylpentene, polyamide resins such as nylon 6 and nylon 66, polyethylene terephthalate, polybutylene terephthalate, polyethylene-2, and the like.
Polyester resins such as 6-naphthalate, poly-1,4-cyclohexane dimethylene terephthalate, and polyethylene isophthalate, and other polyacetal resins;
Polyphenylene sulfide resins and the like can be used, and these resins may be homo resins, copolymers or blends.

Among them, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and polyethylene isophthalate, and copolymer resins or blends thereof are preferred.

Various additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, inorganic particles and organic particles may be added to these resins. In particular, inorganic particles and organic particles are effective for imparting lubricity to the surface of the film and improving the handleability of the film.

The thermoplastic resin of the present invention can be used in any form such as a uniaxially stretched film or a biaxially stretched film. It is particularly preferable to apply the present invention to a process for producing an oriented biaxially oriented film. In order to form a film having a particularly strong orientation in the longitudinal direction and the width direction, in addition to stretching in multiple stages in the longitudinal direction and the width direction,
After the biaxial stretching, the film can be further stretched in the longitudinal direction or the width direction.

Next, the method for producing the thermoplastic resin film of the present invention will be specifically described, but the present invention is not limited to such an example.

Here, an example of polyethylene terephthalate is shown as the thermoplastic resin, but it is not limited to this.

First, for example, polymerized polyethylene terephthalate pellets are vacuum-dried at 180 ° C. for 5 hours, then supplied to an extruder heated to a temperature of 270 to 300 ° C., and extruded from a T-die into a sheet. The melted sheet is brought into close contact with the drum cooled to a drum surface temperature of 25 ° C. by electrostatic force and solidified to obtain a substantially amorphous molded film. The film is heated by a group of heating rolls at 80 to 120 ° C., stretched longitudinally in one or more stages three to six times in the longitudinal direction, and conveyed while being cooled by a group of rolls at 20 to 50 ° C.

Subsequently, while being guided to a stenter and holding both ends of the uniaxially stretched film with clips, 80 to 14
Preheat in a hot air atmosphere heated to 0 ° C, and
The transverse stretching process is performed 6 times. Thereafter, it is preferable to perform heat treatment at a temperature equal to or higher than the transverse stretching temperature and equal to or lower than the melting point of the film.
Thereafter, it is preferable to cut and separate both end portions of the film taken out from the stenter from the viewpoint of uniformity in the width direction.

Thereafter, a thermal relaxation treatment is performed. It is preferable that the heat relaxation treatment is performed without restricting the width direction of the film in a non-contact state in which the film is floated. Specifically, air heated near the temperature for the heat relaxation treatment is applied to one side of the film. It is more preferable that the film is sent only to lift the film, and the heat relaxation treatment is performed while running the film so as to draw a curved surface. At that time, the running tension is 0.15 to 1.5
MPa is preferable, and 0.2 to 1 MPa is more preferable.
Processing time is preferably 1 to 90 seconds, and 2 to 60 seconds.
Seconds are more preferred.

Next, the heat-relaxed film is guided to the stenter again and heat-fixed while holding both ends of the film with clips. It is preferable that the processing temperature of the heat setting processing is higher than the processing temperature of the thermal relaxation processing. Next, it is preferable to cool at 120 to 210 ° C. after the heat treatment. In the heat setting treatment and / or the cooling, a heat relaxation treatment in the width direction may be performed.

Of course, the processing conditions (temperature, time, etc.) in the stenter are appropriately changed and optimized, and the width is relaxed in the width direction while cooling after the heat treatment to suppress the heat shrinkage in the width direction. Is also preferable.

The thus obtained film is subjected to a corona discharge treatment as required, gradually cooled to room temperature, and wound up, whereby the thermoplastic resin film of the present invention can be obtained.

[0035]

[Evaluation method of physical property values] (1) Thermal characteristics A robot DSC "RDC220" manufactured by Seiko Denshi Kogyo Co., Ltd. was used as a differential scanning calorimeter, and a disk station "SSC / 52" manufactured by the company was used as a data analyzer.
Using “00”, about 5 mg of a sample was melted and held at 300 ° C. for 5 minutes on an aluminum saucer, quenched and solidified in liquid nitrogen, and then heated from room temperature at 20 ° C./minute. Based on the transition from the glassy state to the rubbery state observed at this time, the straight line that is equidistant in the vertical axis direction from the extended straight line of each baseline and the curve of the step change portion of the glass transition intersects The temperature was taken as the glass transition point (Tg). (2) thermal dimensional stability width 10 mm, the sample was sampled in the length 250 mm, a straight line is drawn to be about 200mm intervals, the length of the interval measured by profile projector, and L ₀ (mm) . Next, the sample was kept in a hot air oven heated to 150 ° C. without load for 30 minutes, and then cooled at room temperature for 2 hours. Then, the distance between straight lines was accurately measured by a universal projector,
L ₁ (mm). From this measurement result, the following formula was used to calculate, and the average value of the five samples was defined as the thermal dimensional stability. This evaluation was measured in each of the longitudinal direction and the width direction of the film.

Thermal dimensional stability = ((L ₀ −L ₁ ) / L ₀ )
× 100) (%) (3) Uniformity in the width direction Difference z between the maximum value and the minimum value of the orientation angle in the film width direction
The ratio of (°) to the film width Lt (m) is z / Lt.
(° / m), and the uniformity of physical properties in the film width direction was determined as follows. The orientation angle was determined by using a polarizing microscope with white light as a light source, and calculating the narrow angle between the orientation main axis and the film width direction from the extinction value, and setting the orientation angle (°). The main orientation axis was set at 0 ° in the width direction and 90 ° in the direction (longitudinal direction) perpendicular to the width direction.

Good: z / Lt (° / m) is 15 ° / m or less.

Δ: z / Lt (° / m) is 15 to 20 ° /
m or less.

X: z / Lt (° / m) exceeds 20 ° / m.

In the three-level evaluation, ○ and Δ are levels that can be judged to be practicable, and X is a level that can be judged to have no practical value. (4) Flatness The film cut to A4 size was placed on a cork board, the film was squeezed with a stick around which a nonwoven fabric was wound, and air was removed. Then, the flatness was visually determined as follows.

：: No part raised from the cork plate was observed.

△: Three or less portions lifted from the cork board.

X: The part that has risen from the cork plate exceeds three or more places.

In the three-level evaluation, ○ and Δ are levels that can be judged to be practicable, and X is a level that can be judged to have no practical value.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 measured in o-chlorophenol was used. When thermal characteristics were measured using DSC, the Tg was 75 ° C. The polyethylene terephthalate pellets are mixed at 180 ° C. for 5 minutes.
After vacuum drying for an hour, the mixture was supplied to an extruder heated to 270 to 300 ° C. and formed into a sheet from a T-die. Further, this film was adhered and solidified by electrostatic force on a cooling drum having a surface temperature of 25 ° C., and was uniaxially stretched in a longitudinal direction at 90 ° C. by 3.3 times at one stage.

Subsequently, the uniaxially stretched film was guided to a stenter while gripping both ends of the film with clips, and was stretched four times in the horizontal direction at 95 ° C., and was directly stretched in the stenter at 180 ° C. while maintaining the widthwise interval. After heat treatment, the film was taken out from the stenter. The edge portion of the film taken out was cut and separated and subjected to a heat relaxation treatment. The heat relaxation treatment was performed at a traveling tension of 0.5 MPa, a treatment time of 20 seconds, and a treatment temperature of 180 ° C. in an apparatus for floating a film by air force.

While holding both ends of the heat-relaxed film again with clips, the film was guided to a stenter and heat-treated at 200 ° C. to obtain a thermoplastic resin film having a thickness of 40 μm.

Table 1 shows the physical properties of the obtained film.
A film having excellent thermal dimensional stability, flatness, and uniformity in the width direction was obtained.

Example 2 A thermoplastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that the treatment temperature of the heat setting treatment was changed to 160 ° C.

Table 1 shows the properties of the obtained thermoplastic resin film. A film having excellent flatness and uniformity in the width direction was obtained.

Example 3 A thermoplastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that the thermal relaxation treatment was performed without cutting and separating the edge portion of the film.

Table 1 shows the properties of the obtained thermoplastic resin film. A film having excellent thermal dimensional stability and flatness was obtained.

Example 4 A thermoplastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that the heat treatment was not performed immediately after the transverse stretching in the stenter.

Table 1 shows the properties of the obtained thermoplastic resin film. A film having excellent thermal dimensional stability and uniformity in the width direction was obtained.

Example 5 A thermoplastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that the running tension during thermal relaxation was changed to 2 MPa.

Table 1 shows the properties of the obtained thermoplastic resin film. A film having excellent flatness and uniformity in the width direction was obtained.

Comparative Example 1 A plastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that heat fixing after thermal relaxation was not performed.

Table 1 shows the properties of the obtained thermoplastic resin film. Poor thermal dimensional stability and uniformity in the width direction.

Comparative Example 2 A thermoplastic resin film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that the temperature of the heat treatment was changed to 220 ° C. and the heat setting after the thermal relaxation was not performed.

Table 1 shows the properties of the obtained thermoplastic resin film. The uniformity in the width direction is significantly poor.

[0062]

[Table 1]

[0063]

According to the present invention, it is possible to obtain a thermoplastic resin film having excellent thermal dimensional stability, flatness, and uniformity in the width direction with high productivity.

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Claims (6)

[Claims] 1. A running longitudinally stretched thermoplastic resin film,
Lateral stretching, heat setting, a method of producing a thermoplastic resin film by performing each treatment of heat relaxation, the transverse stretching, heat relaxation, the thermoplastic resin film characterized by performing the above treatment in the order of heat fixing Production method. 2. The method for producing a thermoplastic resin film according to claim 1, wherein a heat treatment is further performed after the transverse stretching treatment and before the heat relaxation treatment. 3. The thermoplastic resin according to claim 1, wherein the thermal relaxation treatment is performed at a running tension of 0.15 to 1.5 MPa for 1 to 90 seconds without restricting the width direction of the film. A method for manufacturing a resin film. 4. The thermoplastic resin according to claim 1, wherein the film is heat-relaxed by cutting off both side edges of the film from the film immediately before the heat-relaxation treatment. Film production method. 5. The method for producing a thermoplastic resin film according to claim 1, wherein said thermoplastic resin is a polyester resin. 6. The treatment temperature of the heat setting treatment after the heat relaxation treatment is as follows:
The method for producing a thermoplastic resin film according to any one of claims 1 to 5, wherein the temperature is higher than a treatment temperature of the thermal relaxation treatment.