JP4945841B2 - Manufacturing method of polyamide resin film and polyamide resin film - Google Patents

Description

【表２】

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polyamide resin film, and more particularly to a method for producing a polyamide resin film having uniform physical properties in the width direction.
[0002]
[Prior art]
Thermoplastic resin films, especially biaxially oriented polyester-based, polyamide-based, polyolefin-based, polyvinyl-based resins, polyphenylene sulfide, and other films are used for packaging and industrial applications, and many other applications. It is desirable that the same physical property value be obtained in any part in the width direction.
[0003]
However, it has been extremely difficult to make the physical properties in the width direction of the product film uniform by the conventional manufacturing method. The reason for this is that both ends of the film in the tenter are constrained by clips that are gripping means, whereas the central part of the film is less affected by the gripping means and the restraining force is weak, and the longitudinal stretching caused by the stretching process It has been found that the central portion of the film is delayed with respect to the end portion held by the clip due to the influence of the stress and the shrinkage stress generated by the heat setting process. And in the case where transverse stretching and heat setting are continuously performed with the same tenter, if a straight line is drawn along the width direction on the surface of the film before entering the tenter, the straight line is deformed in the tenter and the film is deformed. It changes 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 step, and deforms into a concave shape after the stretching step. Further, at the beginning of the region of the heat setting process, the concave deformation reaches a maximum value, and the curve does not change and passes through the subsequent tenter, and the concave deformation remains in the film exiting the tenter. This phenomenon is called a bowing phenomenon. This bowing phenomenon causes non-uniform physical property values in the width direction of the film. Due to the bowing phenomenon, an orientation main axis inclined further in the vertical direction with respect to the bowing line is generated at the side edge portion of the film, and the angle of the orientation main axis tends to be different in the width direction. As a result, for example, physical property values such as thermal shrinkage rate, thermal expansion rate, and wet expansion rate in the vertical direction differ in the width direction of the film. Due to this bowing phenomenon, troubles such as printing pitch deviation, occurrence of spots, curling, and meandering have occurred in the printing lamination process and the bag making process, which are examples of packaging applications. In addition, base films such as floppy (registered trademark) disks, which are examples of industrial applications, have problems such as a decrease in magnetic recording durability due to in-plane anisotropy.
[0004]
As a technique for reducing or eliminating the bowing phenomenon, Japanese Patent Application Laid-Open No. 50-73978 proposes a film manufacturing method in which a nip roll group is installed between a stretching process and a heat setting process. However, in this technique, the temperature of the intermediate zone where the nip roll is installed is equal to or higher than the glass transition temperature, and the rigidity of the film at the nip point is low, so the effect of improving the bowing phenomenon is low. Japanese Examined Patent Publication No. 63-24459 proposes a process for forcibly advancing only a narrow range near the center by nip roll while gripping both ends of a film after transverse stretching. However, this technique requires the nip roll to be installed in a high temperature region in the tenter and cool the roll and its peripheral devices, and because the film is hot, there is a risk of scratches caused by the roll. poor. Japanese Patent Publication No. 62-43856 proposes a technique in which a film immediately after transverse stretching is cooled to a temperature below the glass transition temperature and then heat-fixed in multiple stages and stretched in the transverse direction at the same time as heat fixing. . However, in addition to the cooling process, this technology is a complicated process of heat-setting in multiple stages and re-stretching, and it is difficult to stably control the atmospheric temperature and film temperature in the tenter for a long time. is there. Japanese Patent Publication Nos. 1-256694 and 1-256696 propose a technique of reversing the running direction of the film to perform transverse stretching and heat fixing. However, this technique has a problem in terms of productivity because the film needs to be wound once to reverse the traveling direction of the film and is an off-line manufacturing method.
[0005]
[Problems to be solved by the invention]
An object of this invention is to provide the manufacturing method of the polyamide resin film which can reduce the generation | occurrence | production of the bowing phenomenon at the time of film manufacture, and can obtain a film with a uniform physical property in the width direction efficiently.
[0006]
[Means for Solving the Problems]
The present invention has the following configuration.
(1) A polyamide resin sheet is stretched 3.1 to 6.0 times in the longitudinal direction using a tenter and then stretched 3.0 times or more in the transverse direction using the tenter. In the method for producing a resin film, the longitudinal stretching is performed under the temperature conditions of the glass transition temperature (Tg) + 10 ° C. or higher and the low-temperature crystallization temperature (Tc) + 40 ° C. or lower of the unoriented polyamide resin sheet. using, without cooling to below the glass transition temperature (Tg) of, the transverse stretching the glass transition temperature (Tg) or higher, are performed by the melting point (Tm) temperature of -20 ° C. or less, after the transverse stretching, A method for producing a polyamide resin film, wherein a relaxation treatment of 20% or less is performed in the longitudinal direction and the lateral direction by the tenter.
(2) The method for producing a polyamide resin film according to the above (1), wherein the tenter is a linear motor type tenter.
(3) A polyamide resin film formed by the method for producing a polyamide resin film according to any one of (1) to (2) .
[0007]
The thickness of the polyamide resin film formed by the production method of the present invention is not particularly limited, and “film” includes so-called “sheet”.
[0008]
In the present invention, “substantially non-oriented” means that the main alignment axis is not defined in a specific direction.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The polyamide resin film produced by the production method of the present invention may be stretched by a tenter and may be a single layer or a composite such as a multilayer structure.
[0010]
In the method for producing a polyamide resin film of the present invention, a substantially unoriented polyamide resin sheet is obtained by using a tenter in the vertical direction to have a glass transition temperature (Tg) of + 10 ° C. or higher and a low temperature crystallization temperature (Tc) of + 40 ° C. After stretching by 3.1 to 6.0 times under the following temperature conditions, the obtained uniaxially oriented film was continuously cooled to below the glass transition temperature (Tg) using the tenter, and the glass transition temperature in the transverse direction. The film is stretched 3.0 times or more under a temperature condition of (Tg) or higher and melting point (Tm) −20 ° C. or lower.
[0011]
When the stretching temperature during the longitudinal stretching is less than (Tg + 10 ° C.), the stretching stress increases remarkably, the effect of reducing the bowing phenomenon does not appear, and breakage frequently occurs during the subsequent transverse stretching. When the stretching temperature during the longitudinal stretching exceeds (Tc + 40 ° C), the thickness unevenness of the obtained polyamide resin film becomes large, the thermal crystallization progresses significantly, the stretching stress increases, and further during the transverse stretching. Breaks occur frequently. Preferably, the stretching temperature during longitudinal stretching is (Tg + 20 ° C.) to (Tc + 30 ° C.).
[0012]
Although the bowing phenomenon is reduced when the draw ratio during longitudinal stretching is less than 3.1 times, the strength in the longitudinal direction of the obtained polyamide resin film is reduced, and when it exceeds 6.0 times, the effect of reducing the bowing phenomenon is reduced. Does not develop, and breakage frequently occurs during the subsequent transverse stretching. Preferably, the draw ratio during longitudinal stretching is 3.3 to 5.0 times.
[0013]
It is one of the characteristics of the present invention that the obtained uniaxially oriented film is continuously stretched without being cooled below the glass transition temperature (Tg) using the same tenter as that used for longitudinal stretching. That is, the uniaxially oriented film is not forcibly cooled but heated and kept warm, and also used for heating for transverse stretching. When the uniaxially oriented film is forcibly cooled and further reheated for transverse stretching, thermal crystallization proceeds significantly, the transverse stretching stress increases, and the effect of reducing the bowing phenomenon does not appear. Thermal crystallization proceeds even at the time of the above-mentioned heat insulation, but the above-described forced cooling and reheating are much slower than in the case, and there is no practical problem.
[0014]
When the stretching temperature during transverse stretching is less than Tg, the stretching stress is remarkably increased and breakage occurs frequently. When the stretching temperature during transverse stretching exceeds (Tm−20 ° C.), the thickness unevenness increases, and thermal crystallization progresses remarkably, stretching stress increases, and breakage occurs frequently. Preferably, the stretching temperature during transverse stretching is (Tg + 20 ° C) to (Tm-40 ° C).
[0015]
If the draw ratio during transverse stretching is less than 3.0, the strength of the polyamide resin film is lowered and thickness spots are likely to increase. Preferably, the draw ratio during transverse stretching is 3.5 to 5.0 times. If the draw ratio during transverse stretching is too high, the stretching stress increases and breakage tends to occur frequently.
[0016]
In the method for producing a polyamide resin film of the present invention, the tenter used for stretching is preferably a linear motor type tenter for driving the clip. By using a linear motor type tenter for driving the clip, the film formation speed is improved compared to the screw type or pantograph type for driving the clip, and in particular, the condition setting of the longitudinal draw ratio can be easily controlled. It becomes easier to obtain a film having more uniform physical properties in the width direction.
[0017]
Furthermore, in the method for producing a polyamide resin film of the present invention, the biaxially oriented polyamide resin film obtained as described above is heat-set by the same tenter as that at the time of stretching, after the transverse stretching. Is preferred. By heat fixing, changes in moisture absorption dimension, dry heat dimension, and boil dimension of the polyamide resin film are reduced, and troubles such as bag-making curl are caused by post-processing and post-processed product dimensional changes. Can be prevented. Further, the relaxation rate in the relaxation treatment during the heat setting step is preferably 20% or less in the vertical direction and / or the horizontal direction, and particularly preferably, the relaxation rate is 5 to 15 in the vertical direction and / or the horizontal direction. % Should be good. If the relaxation rate exceeds 20%, the residual stress generated during stretching in the machine direction and / or the transverse direction cannot be absorbed in the heat setting step, so that a substantial relaxation effect is difficult to appear, and the film is within the tenter. The loosening causes fluttering of the film due to hot air in the tenter, which easily induces film breakage and scratches on the film.
[0018]
Furthermore, in the relaxation treatment, the temperature is preferably (Tm−70 ° C.) to Tm, and particularly preferably (Tm−50 ° C.) to (Tm−5 ° C.). . When the relaxation treatment temperature is less than (Tm-70 ° C), the relaxation effect hardly appears, and when it exceeds Tm, thermal crystallization proceeds significantly and breakage tends to occur frequently.
[0019]
As described above, the method for producing a polyamide resin film according to the present invention includes a substantially unoriented polyamide resin sheet, wherein the clip is driven in a longitudinal direction using a linear motor type tenter, and the unoriented polyamide resin sheet is used. Glass transition temperature (Tg) + 10 ° C. or higher, low-temperature crystallization temperature (Tc) + 40 ° C. or lower under conditions of 3.1 to 6.0 times, and glass transition temperature (Tg) Without cooling to below, the tenter is continuously stretched in the transverse direction so as to be 3.0 times or more under the temperature condition of glass transition temperature (Tg) or higher and melting point (Tm) -20 ° C or lower. Furthermore, it is preferable to perform a heat setting step including a relaxation treatment of 20% or less in the vertical direction and / or the horizontal direction with the tenter.
[0020]
The process for producing the polyamide resin film of the present invention is not particularly limited as long as it is stretched under the conditions described above. For example, the substantially unoriented polyamide resin sheet before stretching is After the polyamide resin raw material which comprises a film is dried, it is obtained by the conventional general methods, such as melt-extrusion with an extruder, cast on a rotating drum from a die, and rapidly solidify by cooling.
[0021]
The following can be considered as the reason why the production of the polyamide resin film of the present invention can reduce the occurrence of bowing reduction and obtain a thermoplastic film having uniform physical properties in the width direction. In the present invention, by controlling the longitudinal stretching to a specific stretching temperature and stretching ratio, the residual heat shrinkage stress generated by the longitudinal stretching can be reduced, and the stretching stress generated during the transverse stretching can be reduced. The phenomenon is reduced. At the same time, by keeping the temperature between the longitudinal stretching and the transverse stretching in the same tenter and not cooling below the glass transition temperature (Tg), the crystallization promoting action that occurs during forced heating to reheating is prevented, and manifests during transverse stretching. Orientation can be easily formed to improve stretchability, and stretching stress generated during transverse stretching can be reduced, resulting in a reduction in the bowing phenomenon. In the case where the transverse stretching and the heat setting are continuously performed with the same tenter, it is confirmed that the bowing phenomenon occurs somewhat even after the stretching process is finished and takes the maximum value immediately after the subsequent heat setting process. There are stretching stress due to stretching and shrinkage stress due to heat setting between the stretching process and heat setting process, but if the temperature of the film in the heat setting process is high, the rigidity of the film becomes low and the center part of the film is in the stretching process It is considered that the bowing phenomenon occurs due to easy deformation to the side. In the case of performing transverse stretching and heat setting using the same tenter, by performing a heat setting process including a relaxation process, a uniform relaxation process can be performed in the film width direction, and the bowing phenomenon is reduced. Therefore, the bowing reduction can be reduced by controlling the relaxation process to a specific condition. Thus, the stretchability of the film is improved, the bowing phenomenon is reduced, and a film having uniform physical properties in the width direction and excellent in handleability during production or use can be economically obtained.
[0022]
The present invention will be described more specifically with reference to test examples and examples. However, the present invention is not limited to these examples, and it is needless to say that the present invention can be implemented with modifications within a range that can meet the gist of the present invention. All of these are possible within the scope of the present invention.
[0023]
Test Example 1 Test Method (1) Glass transition temperature (Tg), low temperature crystallization temperature (Tc), and melting point (Tm)
The unoriented sheets obtained in the production of the thermoplastic resin films of Examples 1 to 3, Reference Examples 4 to 5 and Comparative Examples 1 to 5 were frozen in liquid nitrogen, and after thawing under reduced pressure, they were elevated using a DSC manufactured by Seiko Electronics. The glass transition temperature (Tg), the low-temperature crystallization temperature (Tc) and the melting point (Tm) were calculated from the endothermic exothermic curve obtained by measuring at a temperature rate of 10 ° C./min.
[0024]
(2) Number of breaks As the film formation state, the thermoplastic resin film production of Examples 1 to 3, Reference Examples 4 to 5 and Comparative Examples 1 to 5 was performed under the same conditions for 2 hours, and the number of breaks of the film was measured. .
[0025]
(3) Boeing distortion In the thermoplastic resin film production of Examples 1 to 3, Reference Examples 4 to 5, and Comparative Examples 1 to 5, a straight line was drawn in the width direction on the surface of the unoriented sheet before entering the tenter, and finally The bowing strain (B: unit%) was calculated using the following formula 1 from the state (Boeing line) in which the thermoplastic resin film obtained above was deformed into a linear bow shape.
B (%) = b / W × 100 Formula 1
W (mm): Film width b (mm): Maximum amount of bowing of the bowing line [0026]
(4) Boiling water shrinkage rate oblique difference The polyamide resin films of Examples 1 to 3 and Comparative Examples 1 to 3 are each 21 cm square from the central part of the full width and the position (end part) of 40% of the full width from the center to the left and right A cut sample is used. Draw a 20cm diameter circle centered on the center of each sample, and draw straight lines that pass through the center of the circle in the 0 °, 45 °, 90 °, and 135 ° directions when the longitudinal direction of the polyamide resin film is 0 °. Measure the diameter of the circle in each direction and make it the length before processing. Each of the above samples is heated in boiling water for 30 minutes, and then taken out to remove moisture adhering to the surface and air-dried. After air-drying, the diameter in each direction was measured again, the length after treatment was taken, and the boiling water shrinkage (%) was calculated using the following formula 2.
Boiling water shrinkage rate (%) = (length before treatment−length after treatment) / length before treatment × 100 Formula 2
Furthermore, the absolute value of the difference between the boiling water shrinkage rates in the 45 ° and 135 ° directions when the vertical direction was 0 ° was determined, and the average value of the samples at both ends was taken as the oblique difference (%) in boiling water shrinkage rate.
[0027]
(5) Thickness variation The thermoplastic resin films of Reference Examples 4 and 5 and Comparative Examples 4 and 5 were cut into 1 mx 5 cm strips in the vertical and horizontal directions, respectively, and the thickness gauge (K306C, Anritsu Electric Co., Ltd.) The thickness shape was measured using The following equation 3 was used to calculate thickness spots per meter, and this was repeated 5 times to obtain an average value, which was used as a measured value.
Thickness unevenness (%) = (maximum thickness−minimum thickness) / average thickness × 100 Formula 3
[0028]
2. Test results The results of the test (1) are shown in Examples , Reference Examples and Comparative Examples, and the results of the tests (2) to (5) are shown in Tables 1 and 2.
[0029]
【Example】
Example 1
Nylon 6 pellets (relative viscosity 2.8) are vacuum-dried and then fed to an extruder, melted at 265 ° C, extruded into a sheet from a T-die, applied with high DC voltage, and 20 ° C. The sheet was electrostatically adhered onto the rotating drum and cooled and solidified to obtain an unoriented sheet having a thickness of 200 μm. This unoriented sheet had a glass transition temperature (Tg) of 40 ° C., a low-temperature crystallization temperature (Tc) of 68 ° C., and a melting point (Tm) of 220 ° C. The unoriented sheet is continuously led to a tenter driven by a linear motor system, stretched 3.5 times in the longitudinal direction at a stretching temperature of 65 ° C, and then kept at 65 ° C while continuing to stretch at the same tenter. After stretching 4.0 times in the transverse direction at 120 ° C, it is further cooled by 6% in the longitudinal direction and 6% in the transverse direction at 215 ° C with the same tenter, then cooled and both edges are cut. Removal of a biaxially oriented polyamide film having a thickness of 15 μm was obtained.
[0030]
Example 2
A biaxially oriented polyamide film was obtained in the same manner as in Example 1 except that the longitudinal stretching was performed at a temperature of 75 ° C.
[0031]
Example 3
A biaxially oriented polyamide film was obtained in the same manner as in Example 1 except that the longitudinal relaxation rate during the relaxation treatment was 10%.
[0032]
Reference example 4
Polyethylene terephthalate pellets (intrinsic viscosity 0.65) are vacuum-dried, then supplied to an extruder, melted at 285 ° C, extruded into a sheet form from a T-die, applied with a DC high voltage, and 20 ° C. The sheet was electrostatically adhered onto the rotating drum and cooled and solidified to obtain an unoriented sheet having a thickness of 190 μm. This unoriented sheet had a glass transition temperature (Tg) of 79 ° C., a low-temperature crystallization temperature (Tc) of 135 ° C., and a melting point (Tm) of 265 ° C. The unoriented sheet is continuously led to a tenter that is driven by a linear motor method, stretched 4.5 times in the longitudinal direction at a stretching temperature of 110 ° C., and then kept at 110 ° C. After stretching 4.0 times in the transverse direction at ° C, after further relaxation treatment of 8% in the longitudinal direction and 10% in the transverse direction at 230 ° C with the same tenter, it is cooled and both edges are cut and removed. Thus, a biaxially oriented polyethylene terephthalate film having a thickness of 12 μm was obtained.
[0033]
Reference Example 5
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Reference Example 4 except that the longitudinal stretching was performed at a magnification of 3.5.
[0034]
Comparative Example 1
A biaxially oriented polyamide film was obtained in the same manner as in Example 1 except that the longitudinal stretching was performed at a temperature of 45 ° C.
[0035]
Comparative Example 2
A biaxially oriented polyamide film was obtained in the same manner as in Example 1 except that longitudinal stretching and lateral stretching were performed using different tenters and the temperature between them was 35 ° C.
[0036]
Comparative Example 3
A biaxially oriented polyamide film was obtained in the same manner as in Example 1 except that the longitudinal relaxation treatment was not performed.
[0037]
Comparative Example 4
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Reference Example 4 except that the longitudinal stretching was performed at a magnification of 6.5 times.
[0038]
Comparative Example 5
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Reference Example 4 except that the longitudinal stretching was performed at a temperature of 180 ° C.
[0039]
【Effect of the invention】
According to the production method of the present invention, it is possible to efficiently obtain a polyamide resin film that reduces the occurrence of the bowing phenomenon, does not cause breakage, has small thickness unevenness, and has high uniformity in physical properties in the width direction. Also excellent.
[Table 1]

[Table 2]

Claims (3)

A substantially unoriented polyamide resin sheet is stretched 3.1 to 6.0 times in the longitudinal direction using a tenter, and then stretched 3.0 times or more in the transverse direction using the tenter. In the production method, the longitudinal stretching is performed under a temperature condition of a glass transition temperature (Tg) + 10 ° C. or higher and a low-temperature crystallization temperature (Tc) + 40 ° C. or lower of the unoriented polyamide resin sheet, and subsequently using the tenter. , without cooling to below the glass transition temperature (Tg) of, the transverse stretching the glass transition temperature (Tg) or higher, are performed by the melting point (Tm) temperature of -20 ° C. or less,
A method for producing a polyamide resin film comprising performing a heat setting step including a relaxation treatment of 20% or less in the longitudinal direction and the transverse direction by the tenter after the transverse stretching.   2. The method for producing a polyamide resin film according to claim 1, wherein the tenter is a linear motor type tenter for driving a clip. The polyamide resin film formed by the manufacturing method of the polyamide resin film of Claim 1 or 2 .