JP2009023207A - Polyester film for processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for processing which even when subjected to processing including a process of heating the film, does not wrinkle nor sag and has excellent flatness after processed. <P>SOLUTION: The biaxially oriented polyester film for processing is characterized in that difference between a heat shrinkage ratio at 180°C for 5 minutes in a MD direction and that in a TD direction is <2.1%. Preferably difference between the heat shrinkage ratio at 120°C for 5 minutes in the MD direction and that in the TD direction is <0.6% and more preferably difference between the heat shrinkage ratio at 150°C for 5 minutes in the MD direction and that in the TD direction is <2.1%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a processing polyester film excellent in flatness after processing. Specifically, even when processing including the step of heating the film is performed, the processing polyester that does not cause wrinkles or sag in the film and can have excellent flatness after processing. Related to film.

  Polyester film is excellent in heat resistance, water resistance, chemical resistance, mechanical strength, dimensional stability, etc., and has been used for various industrial applications, and its applications are expanding and diversifying. In such diversification, the required characteristics have become more and more severe, but at present some of the required characteristics have not been fully satisfied.

  Conventionally, it is used for processing based on polyester film, that is, for printing, plate making, release film, adhesive tape, and protective film. Is done. At this time, drying is performed by a method in which the temperature of the film is increased by heating, but the flatness of the film deteriorates as the film shrinks. In recent years, in particular, the speed of the processing process has been increased, so that it has become severe conditions for the film such as increasing the hot air received by the film in the heating process and increasing the temperature. In order to maintain the flatness of the film after such a heating process, the film has been required to have high properties.

  For example, Patent Document 1 describes a release polyester film with less thermal wrinkle during processing, and describes means for providing a release polyester film with less thermal wrinkle by focusing on heat shrinkage stress. Yes. However, in recent severe heating processes, it is difficult to suppress the generation of wrinkles and sagging only by adjusting the heat shrinkage stress, and a high degree of improvement is required.

  In this way, a biaxially stretched polyester film is applied to a coating device for processing and dried, and then wrinkles generated by heating (hereinafter abbreviated as thermal wrinkles), and slack or flat surfaces generated by heating are placed in a flat shape. There is a problem of deterioration of flatness due to deterioration of flatness that sometimes swells (hereinafter abbreviated as thermal blistering). If the flatness after processing is poor, there is a problem that the basic quality of the processed product is deteriorated, and the flatness after processing is the same as before processing, so that heat wrinkles and hot blisters do not occur even after processing. There is a strong desire to improve such properties by improving the base film.

JP 2005-111919 A

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the polyester film for a process with the flatness after a process including a heating process in a base film for a process favorable.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be easily solved by a film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention resides in a biaxially stretched polyester film for processing characterized in that the difference between the MD direction and the TD direction of the heat shrinkage rate at 180 ° C. for 5 minutes is less than 2.1%.

Hereinafter, the present invention will be described in detail.
The film of the present invention requires that the difference between the MD direction (film longitudinal direction) and the TD direction (film lateral direction) of the heat shrinkage rate at 180 ° C. for 5 minutes is less than 2.1%, preferably It is less than 1.9%, more preferably less than 1.8%. When the difference in shrinkage between the MD direction and the TD direction is large, distortion is generated in the process in which the temperature of the coating process is applied, and thermal wrinkles and thermal blisters are generated to deteriorate the flatness after processing. Similarly, the difference between the MD direction and the TD direction of the heat shrinkage rate at 120 ° C. for 5 minutes is preferably less than 0.6%, more preferably 0.4% or less, and particularly preferably 0.3% or less. Further, the difference between the MD direction and the TD direction of the heat shrinkage rate at 150 ° C. for 5 minutes is preferably less than 2.1%, and more preferably 1.5% or less. If the difference between the MD direction and the TD direction of the heat shrinkage rate is within a certain range, distortion at each temperature in the coating process and the drying process is less likely to occur, and the flatness after processing is minimized. It can be suppressed.

  Furthermore, the heat shrinkage rate in the MD direction and the TD direction at 180 ° C. for 5 minutes is 7% or less, further 3% or less, particularly 1% or less, and the heat shrinkage rate in the TD direction at 150 ° C. for 5 minutes. It is preferably 1.0% or less, more preferably 0.5% or less, respectively, which is desirable because the absolute amount of shrinkage can be kept low and the flatness after processing can be highly satisfied.

  In addition, when the thickness uniformity is poor, a so-called gauge band is formed, non-uniform distortion occurs during processing, and flatness after processing is impaired, so the method described in the embodiment of the present invention It is desirable that the thickness unevenness measured in step 5 is 5% or less, more preferably 4% or less. When the elongation rate is large, the temperature is unevenly increased due to elongation in the coating apparatus, and the flatness after processing is deteriorated. Therefore, the film thickness is desirably 15 mm or less per 1 m of the film width.

  The polyester film as used in the present invention refers to a film extruded by a single layer extrusion method or a coextrusion method in which all layers are co-melt extruded from a die, and then heat-set as necessary after biaxial stretching. Hereinafter, although a single layer film is demonstrated, in this invention, as long as the objective is satisfy | filled, it is not limited to a single layer polyester film, The multilayer of two or more layers may be sufficient.

  In the present invention, the polymer constituting each layer of the film is a polyester obtained using aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 80% or more of the repeating structural units are ethylene terephthalate units or ethylene-2, Refers to polyester having 6-naphthalate units. And you may contain other 3rd components on the conditions which do not deviate from said range.

  As the aromatic dicarboxylic acid component, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, 4,4′-diphenylcarboxylic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid, etc.) can be used. As the glycol component, in addition to ethylene glycol, for example, one or more of diethylene glycol, triethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be used.

  The intrinsic viscosity (IV) of the polyester composition used is usually 0.52 to 0.75, preferably 0.55 to 0.70, and more preferably 0.58 to 0.67. When the IV value is less than 0.52, heat resistance, mechanical strength, and the like, which are excellent characteristics of the polyester film when used as a film, tend to be inferior. On the other hand, when the IV value exceeds 0.75, the load may be excessively increased in the extrusion process during the production of the polyester film, and the productivity may be lowered.

  The total film thickness of the polyester film of the present invention is usually 25 to 350 μm, and various thicknesses are used depending on the application.

  In order to improve workability, the film of the present invention preferably has a roughened surface to impart appropriate slipperiness to the film. For this purpose, fine inert particles can be added. As the fine inert particles for imparting slipperiness, those having an average particle size of 0.5 to 3.0 μm are preferable. When the average particle size is less than 0.5 μm, workability tends to be inferior. Moreover, in the particle | grains with an average particle diameter exceeding 3.0 micrometers, the planarity of the film surface may be impaired or transparency may be impaired. The total amount of inert particles added is usually 0.005 to 1.0% by weight, preferably 0.01 to 0.7% by weight. When the addition amount of the inert particles is less than 0.005% by weight, the winding property of the film tends to be inferior. Moreover, when the addition amount of an inert particle exceeds 1.0 weight%, the degree of the roughening of a film surface will become large too much, and there exists a tendency for film transparency to be impaired.

  Examples of inert particles that can be used in the present invention include silicon oxide, titanium oxide, zeolite, silicon nitride, boron nitride, celite, alumina, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, calcium phosphate, Lithium phosphate, magnesium phosphate, lithium fluoride, aluminum oxide, silicon oxide, titanium oxide, kaolin, talc, carbon black, silicon nitride, boron nitride, and a crosslinking amount as described in JP-B-59-5216 Although molecular fine powder can be mentioned, it is not limited to these. In the present invention, the inert particles to be blended may be a single component, or two or more components may be used simultaneously.

  The film may be subjected to a discharge treatment or a coating layer for imparting workability in the winding process, imparting easy adhesion of the coating agent, or imparting antistatic properties. Prior to these treatments, a chemical treatment, a discharge treatment or an undercoat coating layer may be applied.

  Although the manufacturing method of the polyester film for a process of this invention is demonstrated concretely, as long as the structural requirements of this invention are satisfied, it is not specifically limited to the following illustrations.

  If necessary, polyester containing a predetermined amount of inert particles is supplied to a melt extrusion device, heated to a temperature equal to or higher than the melting point of the polyester polymer, the molten polymer is extruded from a slit die, or polyesters with different additives are used. Each melted, melted polymer is joined and laminated in a laminar flow in the extrusion die, extruded from a slit die, rapidly cooled and solidified on the rotary cooling drum to a temperature below the glass transition temperature, substantially An unoriented sheet in an amorphous state is obtained. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the machine direction, and then stretched 2 to 6 times at 90 to 160 ° C. in the transverse direction. Heat treatment is preferably performed at ˜250 ° C. for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary. In order to make the heat shrinkage rate within the range of the present invention, it is preferable to adjust the heat treatment temperature and the relaxation rate.

  In order to improve the required properties according to the required properties when processing the film of the present invention, for example, easy adhesion to printing, antistatic properties, weather resistance and surface hardness, if necessary, after the longitudinal stretching, You may perform what is called an in-line coating which apply | coats before a tenter entrance and dries in a tenter. Such a coat may be either single-sided or double-sided. The coating material is preferably an aqueous system or an aqueous dispersion system in the case of in-line coating.

  The film of the present invention thus obtained can ensure a high degree of flatness even after various processes including a heating step. In the present invention, the advanced effect can be exhibited particularly for processing including a step of heat treatment at a temperature of 130 ° C. or higher.

  According to the present invention, it is possible to easily provide a biaxially stretched polyester film for processing having good flatness of the processed film, and the industrial value of the present invention is high.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the measurement and determination of various characteristics in the present invention were performed by the following methods.

(1) Heat shrinkage (SMD, STD)
Using a hot-air circulating furnace manufactured by Taibai Manufacturing Co., Ltd., heat-treated for a predetermined time in an atmosphere of measurement temperature in a film tension direction and a transverse direction in a tension-free state, and measure the length of the sample before and after that. The heat shrinkage ratio was calculated by using the average value of 5 pieces each. The heat shrinkage rates in the vertical direction and the horizontal direction are SMD and STD, respectively.

Heat shrinkage (%) = (l ₀ −l ₁ ) / l ₀ × 100
(In the above formula, l ₀ represents the sample length (mm) before heat treatment, and l ₁ represents the sample length (mm) after heat treatment)
When l ₀ is smaller than l ₁ (in the case of expansion), it is represented by − (minus).

(2) Thickness unevenness of film (%)
Using a continuous film thickness measuring instrument (using an electronic micrometer) manufactured by Anritsu Co., Ltd., the film was measured in the vertical and horizontal directions, and the 3 m length was calculated from the following equation. About the horizontal direction, the film was connected and it measured as 3 m.
Thickness unevenness = (maximum film thickness−minimum film thickness) ÷ average film thickness × 100

(4) Flatness Apply a tension of 10 kg / m with an off-line coating machine, cut the sample that has been heated and dried in a hot air oven at a temperature of 180 ° C from the roll, and place the film on a flat desk to obtain flatness. confirmed. Practically, it must be above the ○ level.

A: The processed film remains flat and no sagging or blistering is observed. ○: Sag or blistering seen in the processed film is slightly seen. X: Clear sagging or blistering is seen in the processed film. Example 1:
Polyethylene terephthalate containing an intrinsic viscosity of 0.65 and containing added particles was melt-extruded at 280 to 300 ° C., and cast to a cooling drum while using an electrostatic adhesion method to obtain an amorphous film. This film was stretched 3.5 times in the longitudinal direction at 90 ° C., then stretched 3.5 times in the transverse direction at 110 ° C., and heat treated at 210 ° C. to obtain a polyester film. A polyester film having a thickness of 75 μm was obtained.

Example 2:
A polyester film was obtained in the same manner as in Example 1 except that the heat treatment temperature was 230 ° C. and the relaxation amount was 3% in Example 1.

Example 3:
A polyester film was obtained in the same manner as in Example 1, except that the heat treatment temperature was 220 ° C. and the amount of relaxation was −0.1%.

Example 4:
A polyester film was obtained in the same manner as in Example 1, except that the heat treatment temperature was 240 ° C. and the relaxation amount was 5% in Example 2.

Example 5:
A polyester film was obtained in the same manner as in Example 4 except that the film was stretched 2.8 times in the longitudinal direction and 2.8 times in the lateral direction in Example 4 and a relaxation amount of 3% was applied.

Example 6:
In Example 5, a polyester film was obtained in the same manner as in Example 5 except that the film was stretched 3.5 times in the vertical direction and 3.5 times in the horizontal direction.

Comparative Example 1:
A polyester film was obtained in the same manner as in Example 6 except that the 0.2% relaxation amount was increased in Example 6.

  The characteristics of the collected polyester film are summarized in Table 1 below.

  The film of the present invention can be suitably used, for example, for printing, plate making, release film, adhesive tape, and protective film.

Claims (5)

A biaxially stretched polyester film for processing characterized in that the difference between the MD direction and the TD direction at 180 ° C. for 5 minutes in heat shrinkage is less than 2.1%. The biaxially stretched polyester film for processing according to claim 1, wherein the difference between the MD direction and the TD direction of the heat shrinkage rate at 120 ° C for 5 minutes is less than 0.6%. The biaxially stretched polyester film for processing according to claim 1 or 2, wherein the difference between the MD direction and the TD direction of the heat shrinkage at 150 ° C for 5 minutes is less than 2.1%. The biaxially stretched polyester film for processing according to any one of claims 1 to 3, wherein the heat shrinkage in the MD direction and the TD direction at 180 ° C for 5 minutes is 7% or less. The biaxially stretched polyester film for processing according to any one of claims 1 to 4, wherein the heat shrinkage in the TD direction at 150 ° C for 5 minutes is 1.0% or less.