JP2008260837A - Polyamide resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polyamide films well balanced in several physical properties, and excellent in physical properties, by controlling granular microcrystalline structure of films in simultaneous biaxial drawing. <P>SOLUTION: An polyamide resin film supporting 1-1,000 polyamide-originated microcrystals on a region of 100×100 μm of the film surface is provided, which microcrystals have 0.1-10 μm particle diameter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyamide resin film, and more particularly to a polyamide resin film having a microcrystalline structure.

  Polyamide resin films are widely used as packaging films because of their pinhole resistance, impact resistance, heat resistance, flexibility, and other characteristics. The film is required to have various performances depending on the application. Among them, there are conflicting characteristics and it is very difficult to satisfy all the required performance.

  Moreover, when manufacturing a film, there exists a problem that a film physical property varies in the width direction or a length direction. In particular, when the variation becomes large, only the central part of the produced film roll may be used, and the production efficiency becomes very low. Also, if the balance between the physical properties of the film in the machine direction (MD direction) and the transverse direction (TD direction) is large, when the film is processed into a product, the product strength becomes anisotropic and the overall strength is insufficient. There is a problem that the usability becomes very bad.

  There have been few reports on the correlation between the physical property balance of the film and the crystal structure of the film. On the other hand, there are examples of studies regarding oblique differences such as the thermal contraction rate between the film center and the edge, which are called the bowing phenomenon (Patent Documents 1 and 3). However, the bowing phenomenon focuses only on the variation in the film width direction, that is, the lateral direction, and does not refer to the variation in the physical properties in the longitudinal direction and / or the lateral direction of the film.

Examples of controlling the crystal structure of the film include those in Patent Documents 1 to 4. Patent Documents 1 and 2 are methods for controlling the crystal state by adding an inorganic substance, and the purpose is limited to suppression of the bowing phenomenon or improvement of slipperiness. Patent Document 3 is intended to improve the bowing phenomenon, and Patent Document 4 is only intended to suppress S-curl.
Japanese Patent Laid-Open No. 2005-146032 JP 2002-086555 A JP 2001-341198 A JP-A-8-267469

  Conventionally, various studies have been made, such as changing manufacturing conditions, in order to draw out the properties of polyamide resins when manufacturing polyamide resin films. However, when changing manufacturing conditions, it is difficult to stably produce a film by changing only one condition. That is, it is necessary to change and adjust many conditions such as the temperature of the polyamide resin, the moisture content, the temperature of the cast roll, the stretching temperature, the stretching ratio, and the winding speed. In addition, there are cases where films are manufactured using a plurality of machines in a film manufacturing factory. However, there are differences between the film manufacturing machines, and the adjustment of manufacturing conditions is very complicated, and films with the same physical properties under the same conditions are required. Control such as manufacturing is very difficult, and no single index has been found that can control manufacturing conditions. Furthermore, it is extremely difficult to efficiently control the physical properties of multiple films, such as reducing the strength when attempting to improve transparency, and increasing the thickness difference (variation) in the film width direction, that is, the transverse direction, when attempting to improve the strength. It is.

  Accordingly, the present invention seeks to solve the problems encountered when trying to produce a polyamide resin film having an excellent balance of physical properties.

  The present invention provides a polyamide resin film in which various physical properties are balanced by expressing and controlling a specific microcrystalline structure derived from a polyamide resin in a polyamide film.

  The present inventors have found that by controlling the size and distribution of microcrystals, it is possible to produce a polyamide resin film having a balance of physical properties with good productivity, and have reached the present invention.

  That is, the gist of the present invention is as follows.

  (1) A polyamide resin film having 1 to 1000 microcrystals derived from a polyamide resin having a particle size of 0.1 to 10 μm in a range of 100 × 100 μm on the film surface.

  (2) The particle size of 70 or more of arbitrary 100 crystallites derived from the polyamide resin is in the range of 0.5 to 1.5 times the average particle size of the 100 crystallites. (1) The polyamide resin film characterized by these.

  (3) The polyamide resin film according to (1) or (2), wherein the haze is 5% or less.

  (4) The polyamide resin film according to any one of (1) to (3), wherein the crystal perfection is 70% or more.

  (5) The ratio of the tear propagation resistance in the longitudinal direction and the transverse direction of the film is (longitudinal tear propagation resistance) / (lateral tear propagation resistance) = 0.7 to 1.3 The polyamide resin film according to any one of (1) to (4),

  (6) The ratio (T0 / T1) between the thickness (T0) of the central portion and the thickness (T1) of the end portion in the film width direction is 0.90 to 1.10 (1) to (1) Any polyamide resin film up to 5).

  (7) The tensile strength of the film is 180 MPa or more, and the ratio of the tensile breaking elongation in the machine direction and the transverse direction (horizontal / longitudinal) is 0.9 to 1.5. Any polyamide resin film up to (6).

  (8) The polyamide resin film according to any one of (1) to (7), wherein the polyamide resin is nylon 6.

  (9) A method for producing a polyamide resin film according to any one of (1) to (8), wherein the polyamide resin film is produced by a simultaneous biaxial stretching method. .

  By controlling the microcrystalline structure, the polyamide resin film of the present invention can produce a film with a balance of various film properties by a simple method using a conventional manufacturing apparatus, and the industrial utility value is extremely high. .

Hereinafter, the present invention will be described in detail.
An object of the present invention is to control the transparency, crystal perfection, thickness unevenness, strength, and physical property balance (variation) of a film by paying attention to one variable called microcrystals.

  The microcrystal in the present invention will be described. The microcrystal in the present invention is observed by an optical microscope and is different from a microcrystal measured by X-ray diffraction or the like.

  When a film is produced by the biaxial stretching method, a granular microcrystalline structure that can be observed even with a magnification of an optical microscope may be formed. This microcrystalline structure changes its form and changes its appearance density and size by adjusting the film forming conditions.

  These microcrystals are different from the spherulite structure because no peculiar Maltese cross pattern is observed even when polarized. In addition, a granular microcrystalline structure is not observed only by longitudinal stretching or lateral stretching, and is formed only when various conditions such as stretching ratios of longitudinal and lateral stretching are met. In particular, it is a unique structure that is not observed in the sequential biaxial stretching method and appears only when the simultaneous biaxial stretching method is limited.

  In a polyamide resin film, crystallization proceeds during stretching, and the crystals are oriented in the stretching direction. In sequential stretching, crystallization progresses during the first longitudinal stretching, and in subsequent lateral stretching, crystallization progresses less than in longitudinal stretching because it has already been crystallized in the longitudinal stretching. It becomes an oriented crystal. For this reason, it is thought that a granular microcrystal does not arise. However, in the simultaneous biaxial stretching, longitudinal and lateral stretching are simultaneously performed, so that crystallization proceeds in a well-balanced manner centering on the longitudinal and lateral directions, and it is considered that granular microcrystals are generated.

  The present inventors have found that this microcrystal strongly correlates with film physical properties, and by controlling the microcrystalline structure of the film, it is possible to produce a polyamide resin film satisfying various physical properties in a balanced manner. Reached.

  The polyamide resin film of the present invention has 1 to 1000 microcrystals derived from a polyamide resin having a particle size of 0.1 to 10 μm (hereinafter referred to as “polyamide microcrystals”) in the range of 100 × 100 μm on the film surface. There are.

  As mentioned above, it is important that the size of the polyamide crystallites is 0.1 to 10 μm in terms of particle size, preferably 0.5 to 8 μm, more preferably 1 to 5 μm. When it is smaller than 0.1 μm, there is no effect of reducing the thickness unevenness, haze, tensile elongation at break, and tear propagation resistance ratio (longitudinal / lateral). On the other hand, if it is larger than 10 μm, the haze is increased and the physical properties are deteriorated, and the operability is deteriorated such as frequent stretching and cutting. The polyamide crystallites having a particle size of 0.1 to 10 μm are required to be present in the range of 100 × 100 μm in the range of 100 × 100 μm and preferably in the range of 2 to 200 at any position on the film surface. . As a result, a well-balanced film can be obtained in which the thickness unevenness at the center and the end of the film is small and the tear propagation resistance and the aspect ratio of tensile elongation at break are small.

  When a plurality of measurement ranges of 100 × 100 μm are set on the film surface, a balanced film cannot be obtained unless even one of them satisfies the above conditions. If these conditions are not satisfied, the thickness unevenness at the center and the end of the film will increase, and the aspect ratio of the tear propagation resistance and the tensile elongation at break will increase. You can't get it. When more than 1000 polyamide crystallites having a particle size of 0.1 to 10 μm are present in the range of 100 × 100 μm, the haze of the film increases.

  In the polyamide resin film of the present invention, the particle diameter of 70 or more of arbitrary 100 crystallites derived from the polyamide resin is 0.5 to 1.5 times the average particle diameter of the 100 crystallites. It is preferable to be within the range. Within this range, crystal integrity is high and tensile strength is increased.

  When the polyamide crystallites that fall within the range of 0.5 to 1.5 times the average particle size of the polyamide crystallites are less than 70 out of 100, that is, less than 70%, that is, when the dispersion of the particle size is large, In other words, when the grain size is unevenly distributed on the small or large diameter side, the crystal integrity is lowered and the tensile strength is reduced. In particular, when the particle diameter of 70 or more of 100 polyamide crystallites exceeds 1.5 times the average particle diameter of these 100 crystallites, that is, the particle diameter is unevenly distributed on the large diameter side. In such a case, the tendency for the crystal integrity to decrease and the tensile strength to decrease increases.

  In the polyamide resin film of the present invention, the crystal perfection is preferably 70% or more. The crystal perfection is a value obtained from the following formula (1) where d is the interplanar spacing. When the film is analyzed by an X-ray diffraction method, the observed crystal has a structure close to a perfect crystal. It shows the indicator of whether or not.

Crystal perfection = {[d (200) / d (002), (202)]-1} /0.211×100
... (1)

  When the crystal perfection is 70% or more, there is an advantage that the tensile strength of the film is high. If the crystal perfection is less than 70%, the film strength tends to decrease.

  In the polyamide resin film of the present invention, the ratio of tear propagation resistance in the machine direction and transverse direction of the film is (longitudinal tear propagation resistance) / (lateral tear propagation resistance) = 0.7- It is preferably 1.3. By being in this range, the film has a good balance between vertical / horizontal properties and excellent dimensional stability. With such a film, there is no printing misalignment during printing and bag making and no twisting of the bag product, and a good bag product can be obtained.

  When (longitudinal tear propagation resistance) / (lateral tear propagation resistance) is not in the range of 0.7 to 1.3, the physical property balance in the vertical / horizontal direction is poor and the dimensional stability is poor. Become a film. In such a film, printing misalignment at the time of printing and bag making, twisting of the bag-made product, etc. occur, resulting in a defective product.

  In the polyamide resin film of the present invention, the ratio (T0 / T1) of the thickness (T0) of the central portion and the thickness (T1) of the end portion in the film width direction is preferably 0.90 to 1.10. More preferably, it is 0.95-1.05. When the thickness is within this range, a film free from sagging and wrinkles can be obtained during film processing. With such a film, it is possible to manufacture a product with high productivity without causing any problems in the printing and lamination processes. Moreover, in such a film, near the full width of the manufactured film can be made into a product, and productivity is high.

  If the ratio (T0 / T1) is out of the range of 0.90 to 1.10, tarmi and wrinkles occur during film processing, and printing misalignment and other processing irregularities occur in the printing process. Moreover, in such a film, since only the center part of the manufactured film becomes a product and the end part becomes waste, productivity is greatly reduced.

  In addition, in this invention, the center part in a film width direction means the center position along the width direction of a film. The end means a position at a distance of 10% of the entire width from the film end along the width direction toward the center. The thickness of the end portion means an average value obtained by measuring both end portions.

  In the polyamide resin film of the present invention, it is preferable that the tensile strength of the film is 180 MPa or more and the ratio of the tensile breaking elongation in the machine direction and the transverse direction (width / length) is 0.9 to 1.5. . Within this range, the strength as a polyamide resin film is sufficient, and it can be used for various packaging materials. Further, when the aspect ratio is in the above-described range, as described above, the film has excellent physical property balance and dimensional stability and is excellent in various processability.

  When the tensile strength of the film is less than 180 MPa, there is a tendency that the strength required for the polyamide resin film is insufficient. On the other hand, if the ratio of tensile elongation at break (horizontal / longitudinal) is out of the range of 0.9 to 1.5, the film becomes inferior in physical property balance and dimensional stability, and the workability is lowered.

  Polyamide resins used in the present invention include polytetramethylene adipamide (nylon 46), polycoupleramide (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (nylon 610), polyendecamide ( Nylon 11), polylauramide (nylon 12), polymetaxylylene adipamide (MXD6), and mixtures thereof. In particular, nylon 6 having high crystallinity is preferably used.

  These resins may contain various additives such as a lubricant, an antioxidant, and a reinforcing agent, as long as they do not greatly adversely affect the physical properties and manufacturability of the film.

  The polyamide resin film is easy to absorb moisture, and causes problems such as a decrease in slip characteristics, wrinkles in the film processing process, and printing whiskers in the printing process. As means for improving the slip property, a method of adding an inorganic lubricant such as silicon oxide, alumina or calcium carbonate, an organic lubricant such as ethylene bisstearylamide, an organic polymer lubricant such as polyolefin or polytetrafluoroethylene is generally used. ing. The addition amount of these lubricants is preferably in the range of 0.01 to 1% by mass.

  When producing the polyamide resin film of the present invention, the simultaneous biaxial stretching method is preferred. In the sequential biaxial stretching method and the inflation method, the granular microcrystalline structure is not observed or very small even if observed. In addition, it is considered that the crystal growth is promoted by stretching, and a granular microcrystalline structure is formed only when the balance of longitudinal stretching and lateral stretching and other conditions are met at the time of crystal growth.

The manufacturing method of the polyamide resin of this invention is demonstrated with reference to drawings.
FIG. 1 is a process diagram of a general method for producing a stretched polyamide film. First, raw material resin pellets are supplied to the hopper 1, plasticized and melted by the melt extruder 2, the melted resin is extruded into a sheet form from the T-die 3 attached to the tip of the extruder 2, and cooled and solidified by the cast roll 4. To do. At this time, the polyamide resin is pressed against the cast roll 4 by air to obtain an unstretched film.

  The temperature setting range of the cast roll 4 is preferably 20 to 80 ° C. If it is less than 20 ° C., it is difficult to obtain the microcrystals in the present invention, and if it exceeds 80 ° C., the obtained microcrystals are too large or the variation in crystal size becomes too large. Inconveniently, the effect of the present invention cannot be obtained.

  The thickness of the air layer interposed between the cast roll 4 and the polyamide resin is relatively thicker at the end than at the center of the roll, but is preferably 50 to 220 μm at any position. More preferably, the thickness is 190 μm.

When the molten sheet is pressed against the cast roll 4 and cooled and solidified, as a method of pressing, generally,
(1) Air nozzle method in which air is blown to both ends of the molten sheet (2) Air knife method in which air is uniformly blown to the molten sheet (3) Electrostatic adhesion method in which charges are deposited on the molten sheet by high voltage electrodes and electrostatically adhered There is. Among these, it is difficult to develop polyamide crystallites by an electrostatic contact method in which the air layer has almost no thickness. When the thickness of the air layer is in the above range by the air knife method or the air nozzle method, polyamide crystallites are easily developed.

  When the thickness of the air layer is less than 50 μm, the degree of crystallinity of the obtained unstretched sheet is too low, and microcrystals are not generated, or even if they are generated, it becomes very small. The average particle size of the polyamide crystallites is less than 0.1 μm. In addition, when the thickness of the air layer exceeds 220 μm, microcrystals grow, large grain boundaries are generated, and the average particle size of polyamide microcrystals in the finally obtained film exceeds 10 μm. Whitening.

  The distance (air layer thickness) between the cast roll 4 and the unstretched sheet obtained by cooling and solidifying the molten sheet can be measured using, for example, a laser focus displacement meter (manufactured by Keyence Corporation).

  In the film manufacturing process, a so-called bowing phenomenon occurs. That is, a phenomenon occurs in which the degree of progress of crystallization varies along the width direction of the film. Therefore, it is not enough to adjust the thickness of the air layer in order to make the physical properties in the width direction and the diagonal direction uniform. Finally, the size and distribution of the microcrystals generated in the process of pressing on the casting roll are finally converted into a film. It is preferable to make it uniform at each position. Control of the air layer alone is not sufficient to bring the crystallite size and distribution at each location of the film within the scope of the present invention.

  That is, the unstretched film is then subjected to a water absorption treatment process in the water tank 5 and then simultaneously stretched in the vertical and horizontal biaxial directions in a stretching process by the film stretching machine 6, and in the form of a take-up roll 7 of a stretched polyamide resin film. It is commercialized.

  This step is important because the size and distribution of the microcrystals are determined by passing an unstretched film with microcrystals through the water bath 5 for the water absorption treatment step. In the water absorption treatment step, it is preferable that the film absorbs water in two or more water absorption tanks having different temperatures, and the temperature of the first stage affects the size and distribution of the microcrystals. Specifically, the temperature of the first-stage water absorption tank is set within a range of 30 to 50 ° C., and the temperature of the water tank top and bottom is within the range of the water tank set temperature ± 8 ° C., preferably the set temperature ± The temperature should be controlled so as to be within the range of 5 ° C., more preferably within the range of the set temperature ± 3 ° C. Here, the upper part of the water tank means an arbitrary point within a range of 15 to 20 cm below the water surface, and the bottom part means an arbitrary point 15 to 20 cm above the bottom of the water tank. By doing in this way, it becomes possible to make 1-1000 polyamide microcrystals whose average particle diameter becomes the above-mentioned predetermined range in the range of 100 × 100 μm on the film surface.

  When the temperature of the first stage water absorption tank is less than 30 ° C., the growth of polyamide microcrystals is inhibited. On the other hand, if this temperature exceeds 50 ° C., wrinkles are likely to enter the unstretched film, and the quality of the resulting stretched film tends to deteriorate. When the temperature of the first stage water absorption tank varies by ± 8 ° C. or more depending on the location in the tank, the distribution of polyamide microcrystals varies, and as a result, the heat shrinkage rate of the polyamide resin film finally obtained through the stretching treatment And variation in elongation at break increases.

  After passing through the first-stage water absorption tank, the moisture content of the film is adjusted to 2 to 10% by mass in the second-stage and subsequent water-absorption tanks. The film is stretched in the range of 5 to 5 times and 2 to 5 times in width, heat-treated in the range of the set temperature 180 to 240 ° C., and then relaxed in the range of 0.1 to 10% to obtain the final polyamide resin film. obtain.

  The polyamide resin film of the present invention is transparent, has a small difference in physical properties in the vertical and horizontal directions, has an excellent balance of physical properties, has close physical properties in any direction and any position of the film, and is easy to handle. Can be used for applications. In particular, gravure printing, offset printing, flexographic printing, letterpress printing, silk screen printing, inkjet printing, etc., various coatings such as easy-adhesion layer, gas barrier layer, antistatic layer, packaging film etc. It is suitable for.

Hereinafter, the present invention will be described specifically by way of examples.
The measurement methods of various physical properties in the following examples and comparative examples were as follows. All measurements were performed in an environment of a temperature of 20 ° C. and a humidity of 65%.

(1) Observation of microcrystalline structure A film sample was cut into a square shape of 50 cm × 50 cm at three points of both end portions and the central portion along the width direction of the film, and 5 cm inside from four corners on the diagonal line of this sample A total of 12 points were measured, 4 points each. Here, the both end portions of the film refer to positions at a distance of 10% of the total width from the film end along the width direction toward the center, and a sample was cut out centering on this end portion. Moreover, when the width | variety of the film was narrow and a square of 50 cm x 50 cm cannot be cut out centering on an edge part, the sample was cut out by making the edge of a film into one side of a square.

  At each observation point, observation was performed at a magnification of 100 to 400 times using a polarizing microscope. The particle size was defined by the longest side of the particle.

The number of crystallites, calculated by counting the microcrystalline granular for any range of 100 × 100 [mu] m in the film surface of the 12 points, as the density is the number per ^{mm 2 (× 10 2 / mm} 2) Expressed. At this time, since microcrystals are also present inside the film, the microscope was focused in the film thickness direction three times, and all the microcrystals observed there were counted. Further, the maximum value and the minimum value of the 12 points were obtained.

  The average particle size was determined for 100 arbitrary crystallites observed at any one of the 12 points. The measurement of whether the particle size of 70 or more of the 100 crystallites is in the range of 0.5 to 1.5 times the average particle size of these 100 crystallites is the observed arbitrary The calculation was performed on 100 crystals.

(2) Film thickness and thickness unevenness Thickness was measured using a thickness meter MT-12B (manufactured by HEIDENHAIN). That is, in the lateral direction of the film, that is, in the film width direction, the thickness at the center position (T0) and the thickness at the position of 10% of the total width from the end toward the center (T1 = average of both ends) were measured. And thickness unevenness was calculated | required from T0 / T1, and 0.90-1.10 was set as the pass.

(3) Tensile strength / elongation It was measured using Autograph AG-1 (manufactured by Shimadzu Corporation). The test piece was a strip having a width of 10 mm and a length of 150 mm, the cell used was 100 kg, the test speed was 500 mm / min, and the chuck interval was 100 mm.

  Regarding the tensile strength, the measurement sample, that is, the test piece, is located at the position of the center of the film and at two positions at both ends at a distance of 10% of the entire width from both ends in the film width direction toward the center. The film was collected in the film longitudinal direction and the film width direction (lateral direction). And the tensile strength was calculated | required about a total of six test pieces, and the average value was made into the tensile strength of the film.

  The elongation is the average value of the measured values measured in the longitudinal direction of the film and the average value of the measured values measured in the transverse direction of the film for each of the center and both ends of the film. It calculated from ratio with the average value of a horizontal direction.

(4) Tear propagation resistance force Measured using Autograph AG-1 (manufactured by Shimadzu Corporation). The cell used was 100 kg or 5 kg, and the test speed was 200 mm / min. The test piece was strip-shaped, had a width of 25 mm, a length of 75 mm, and a slit of 50 mm in the longitudinal direction at the center of the 25 mm width. Test specimens were prepared at five points in the film longitudinal direction and lateral direction at the center and end positions in the width direction of the film in the same manner as in the measurement of tensile strength and elongation, and the average value of the measured values for each test piece was determined. The ratio of the average value in the film longitudinal direction and the average value in the film transverse direction was determined.

(5) Haze It measured using the haze meter NDH2000 (made by Nippon Denshoku Industries Co., Ltd.). Similarly to the measurement of tensile strength and elongation, a test piece of 50 × 100 mm was cut out from the center and end positions in the width direction of the film, attached to a metal plate, and an average value measured twice was used as a measurement value. The haze was 5 or less.

(6) Crystal integrity Measured using a wide-angle X-ray scattering method. That is, measurement was performed using a Rad-X type X-ray diffractometer (manufactured by Rigaku Corporation), and CuKα rays were used as a radiation source. As the sample, 75 pieces cut out in 3 × 3 cm were used. For the (002) plane, an X-ray diffraction peak was measured by a reflection method at an apparatus output of 50 kV and 50 mA, and the plane spacing (d) was calculated. For the (200) plane, the sample was rotated 67.5 °, the X-ray diffraction peak was measured by the transmission method at an apparatus output of 50 kV and 50 mA, and the plane spacing (d) was calculated.

Crystal perfection (%) was calculated according to the following formula (1) as described above.
Crystal perfection = {[d (200) / d (002), (202)]-1} /0.211×100
... (1)

  The crystal perfection was measured at the center and end of the film, and the average value thereof was defined as the crystal perfection of the film. As the value at the end, an average value for both ends was used.

  Crystal perfection is an index showing how close to a perfect crystal a microcrystal (actual crystal in a polyamide resin) is.

[Create master chip]
Nylon 6 resin (A1030-BRF, manufactured by Unitika Ltd.) having a relative viscosity of 3.0 measured in 95% concentrated sulfuric acid at a temperature of 25 ° C. and a concentration of 0.5 g / dl was dried. 6 parts by mass of silicon oxide (Mizusawa Chemical Co., Ltd., Psyroid SY-150), which is an inorganic lubricant, was melt-mixed to prepare a master chip.

Example 1
A dry nylon 6 resin (A1030-BRF, manufactured by Unitika Co., Ltd.) and the above-mentioned master chip are blended, and the blending ratio of the inorganic lubricant is set to 0.05 mass%, and the mixture is put into an extruder, and the temperature is 270. Melted in a cylinder heated to ℃, extruded into a sheet from a T-die orifice, pressed against the cast roll set at 40 ℃ with air blown from the nozzle, cooled by cooling, and unstretched film with a thickness of 180μm Got. When the distance (air layer thickness) between the cast roll and the unstretched sheet was measured using a laser focus displacement meter (manufactured by Keyence Corporation), the minimum value was 92 μm and the maximum value was 157 μm.

  Next, this unstretched film was immersed in the 1st water absorption tank. This 1st water absorption tank was managed so that the temperature of a setting part was 45 degreeC and the temperature of the upper part and the bottom part might be in the range of +/- 3 degreeC with respect to setting temperature. Subsequently, the moisture content was adjusted by allowing the film to contain water in a second water-absorbing tank set at 60 ° C. Then, after guiding to a simultaneous biaxial stretching machine and preheating at 175 ° C., the film was stretched at a stretching temperature of 190 ° C. at a magnification of 3.5 times in the longitudinal direction and 3.3 times in the transverse direction. Subsequently, heat treatment was performed at a temperature of 220 ° C. during the film running process of 3 m, and 3% relaxation treatment was performed to obtain a nylon 6 film having a thickness of 15 μm. The film winding speed was 130 m / min. Table 1 shows the physical properties of the obtained nylon 6 film.

Example 2
A dried nylon 6 resin (A1030-BRF, manufactured by Unitika Ltd.) and the above-mentioned master chip are blended, and the blending ratio of the inorganic lubricant is 0.05% by mass, and the mixture is put into an extruder at a temperature of 260. Melted in a cylinder heated to ℃, extruded into a sheet from a T-die orifice, pressed against the cast roll kept at 60 ℃ by air blown from the nozzle, cooled by cooling, and unstretched film with a thickness of 170μm Got. When the distance (air layer thickness) between the cast roll and the unstretched sheet was measured using the laser focus displacement meter, the minimum value was 103 μm and the maximum value was 185 μm.

  Next, this unstretched film was immersed in the 1st water absorption tank. This 1st water absorption tank was managed so that the temperature of upper part and a bottom part might be in the range of +/- 3 degreeC with respect to setting temperature while setting temperature was 30 degreeC. Subsequently, the moisture content was adjusted by allowing the film to contain water in a second water-absorbing tank set at 60 ° C. Thereafter, the film was guided to a simultaneous biaxial stretching machine, preheated at 175 ° C., and stretched at a stretching temperature of 190 ° C. at a magnification of 3.3 times in the longitudinal direction and 3.3 times in the transverse direction. Subsequently, heat treatment was performed at a temperature of 200 ° C. during a film running process of 3 m, and a 2% relaxation treatment was performed to obtain a nylon 6 film having a thickness of 15 μm. The film winding speed was 180 m / min. Table 1 shows the physical properties of the obtained nylon 6 film.

Example 3
A dry nylon 6 resin (A1030-BRF, manufactured by Unitika Co., Ltd.) and the above-mentioned master chip are blended, and the blending ratio of the inorganic lubricant is set to 0.05 mass%, and the mixture is put into an extruder, and the temperature is 270. Melted in a cylinder heated to ℃, extruded into a sheet from a T-die orifice, pressed against the cast roll set at 50 ℃ by air blown from the nozzle, cooled by cooling, and unstretched film with a thickness of 170μm Got. The minimum value of the air layer thickness measured in the same manner as described above was 61 μm, and the maximum value was 154 μm.

  Next, this unstretched film is immersed in a first water absorption tank whose set temperature is 50 ° C. and whose top and bottom temperatures are controlled to be within a range of ± 5 ° C. with respect to the set temperature. The water was adjusted in the second water absorption tank set at 50 ° C. Thereafter, the film was guided to a simultaneous biaxial stretching machine, preheated at 175 ° C., and stretched at a stretching temperature of 190 ° C. at a magnification of 3.4 times in length and 3.2 times in width. Subsequently, heat treatment was performed at a temperature of 210 ° C. during a film running process of 3 m, and a 2% relaxation treatment was performed to obtain a nylon 6 film having a thickness of 15 μm. The film winding speed was 160 m / min. Table 1 shows the physical properties of the obtained nylon 6 film.

Example 4
A dry nylon 6 resin (A1030-BRF, manufactured by Unitika Co., Ltd.) and the above-mentioned master chip are blended, and the blending ratio of the inorganic lubricant is set to 0.05 mass%, and the mixture is put into an extruder, and the temperature is 270. Melted in a cylinder heated to ℃, extruded into a sheet form from a T-die orifice, pressed against the cast roll cooled to 20 ℃ by air blown from the nozzle, brought into close contact, rapidly cooled, and a 180 μm thick unstretched film Got. At this time, the air layer thickness measured in the same manner as described above had a minimum value of 50 μm and a maximum value of 187 μm.

  Next, the unstretched film is immersed in a first water absorption tank whose set temperature is 45 ° C. and whose top and bottom temperatures are controlled within a range of ± 5 ° C. with respect to the set temperature. Then, moisture adjustment was performed in a second water absorption tank set at 70 ° C. Then, after guiding to a simultaneous biaxial stretching machine and preheating at 175 ° C., the film was stretched at a stretching temperature of 190 ° C. and at a magnification of 3.5 times in length and 3.3 times in width. Subsequently, heat treatment was performed at a temperature of 220 ° C. during the film running process of 3 m, and 3% relaxation treatment was performed to obtain a nylon 6 film having a thickness of 15 μm. The film winding speed was 190 m / min. Table 1 shows the physical properties of the obtained nylon 6 film.

Comparative Example 1
Temperature control of the top and bottom of the first water tank was allowed to ± 10 ° C. with respect to the set temperature of 45 ° C. Other than that was carried out similarly to Example 1, and obtained the nylon 6 film. At this time, the upper temperature of the 1st water absorption tank was 49 degreeC, and the temperature of the bottom part was 33 degreeC. Table 1 shows the physical properties of the obtained nylon 6 film.

Comparative Example 2
The air flow rate from the nozzle was changed so that the air layer thickness had a minimum value of 10 μm and a maximum value of 55 μm. Other than that was carried out similarly to Example 2, and obtained the nylon 6 film. Table 1 shows the physical properties of the obtained nylon 6 film.

Comparative Example 3
The temperature of the cast roll was set to 15 ° C. Otherwise in the same manner as in Example 3, a nylon 6 film was obtained. Table 1 shows the physical properties of the obtained nylon 6 film.

Comparative Example 4
The first water tank was not used. Other than that was carried out similarly to Example 2, and obtained the nylon 6 film. Table 1 shows the physical properties of the obtained nylon 6 film.

Comparative Example 5
A dried nylon 6 resin (A1030-BRF, manufactured by Unitika Ltd.) and the above-mentioned master chip are blended, and the blending ratio of the inorganic lubricant is 0.05% by mass, and the mixture is put into an extruder at a temperature of 260. It is melted in a cylinder heated to ℃, extruded into a sheet form from a T-die orifice, and the minimum value of the distance between the cast roll and the unstretched sheet is set to 90 μm by an air knife casting method, and the surface temperature is 20 ℃. The film was brought into close contact with the cast roll and cooled to obtain an unstretched film having a thickness of 150 μm.

  Although this unstretched film was stretched in the longitudinal direction at a temperature of 55 ° C. and a stretching ratio of 2.7 times by a longitudinal stretching machine composed of heating roller groups having different peripheral speeds, the film was frequently cut and the film could be collected. There wasn't.

  As a countermeasure, the film cutting was reduced by making the distance between the cast roll and the unstretched sheet shorter than the above. Finally, stretching became possible when the minimum value of the distance between the cast roll and the unstretched sheet was 10 μm or less.

  Therefore, the unstretched film thus obtained is stretched in the longitudinal direction at a temperature of 55 ° C. and a stretching ratio of 2.7 times by a longitudinal stretching machine composed of a group of heating rollers having different peripheral speeds. The unidirectionally stretched film is preheated at 60 ° C. in the preheating part, stretched in the transverse direction at a stretching ratio of 3.8 times at a temperature of 90 ° C., subsequently heat-treated at 211 ° C., and then 2% in the transverse direction at a temperature of 210 ° C. Was performed to obtain a nylon 6 film having a thickness of 15 μm. Table 1 shows the physical properties of the obtained nylon 6 film.

Comparative Example 6
The air flow rate from the nozzle was changed so that the air layer had a minimum thickness of 130 μm and a maximum value of 250 μm. Other than that was carried out similarly to Example 2, and obtained the nylon 6 film. Table 1 shows the physical properties of the obtained nylon 6 film.

  As is clear from the results in Table 1, in all of Examples 1 to 4, the microcrystals in the film had an average particle diameter of 0.1 to 10 μm and 1 in the range of 100 × 100 μm with respect to the film surface. Since there were ˜1000 pieces, the film was a well-balanced film in which the thickness unevenness between the central portion and the end portion of the film was small, and the physical property ratio of the film length / width was small. In addition, since the particle size of 70% or more of the microcrystals was within the range of 0.5 to 1.5 times the average particle size, the crystal perfection was as high as 70% or more. The film was high and excellent in physical properties.

  On the other hand, in Comparative Example 1, there was a portion where no microcrystals existed, and the variation in existence density was large, so that the film had a large thickness unevenness and a poor physical property balance. Also, the film roll was bad.

  In Comparative Example 2, although microcrystals exist, the existence density exceeds 1000 at some measurement points, and the haze is deteriorated because the average particle diameter is very small, and the tear propagation resistance and the tensile elongation at break are increased. The film has an unbalanced film with a high aspect ratio.

  In Comparative Examples 3 to 5, since the existence density of the microcrystals was too low, the films had an unbalanced film having a large aspect ratio of the tear propagation resistance and the tensile elongation at break. In particular, Comparative Example 4 had large thickness spots and a poor winding shape. Since Comparative Example 5 was not manufactured by the simultaneous biaxial stretching method but was manufactured by the sequential biaxial stretching method in which the transverse stretching was performed after the longitudinal stretching, the presence of microcrystals as described above The density was too low.

  In Comparative Example 6, there is a portion where microcrystals do not exist, the variation in density is large, the average particle size is too large, haze is poor, the tensile strength is low, the tear propagation resistance and the tensile elongation at break The film was unbalanced with a large aspect ratio.

It is a figure which shows an example of the manufacturing apparatus for manufacturing the polyamide resin film of this invention.

Explanation of symbols

1 Hopper 2 Melt Extruder 3 T-Die 4 Cast Roll 5 Water Tank 6 Film Stretcher 7 Winding Roll

Claims (9)

  A polyamide resin film characterized in that 1-1000 microcrystals derived from a polyamide resin having a particle size of 0.1 to 10 μm are present in a range of 100 × 100 μm on the film surface.   The particle size of 70 or more of arbitrary 100 crystallites derived from polyamide resin is in the range of 0.5 to 1.5 times the average particle size of the 100 crystallites, The polyamide resin film according to claim 1.   3. The polyamide resin film according to claim 1, wherein the haze is 5% or less.   The polyamide resin film according to any one of claims 1 to 3, wherein the crystal perfection is 70% or more.   The ratio of the tear propagation resistance in the machine direction and the transverse direction of the film is (longitudinal tear propagation resistance) / (lateral tear propagation resistance) = 0.7 to 1.3 The polyamide resin film according to any one of claims 1 to 4.   The ratio (T0 / T1) of the thickness (T0) of the central portion and the thickness (T1) of the end portion in the film width direction is 0.90 to 1.10. The polyamide resin film according to claim 1.   The tensile strength of the film is 180 MPa or more, and the ratio of the tensile breaking elongation in the machine direction and the transverse direction (transverse / longitudinal) is 0.9 to 1.5. The polyamide resin film of any one of Claims.   The polyamide resin film according to any one of claims 1 to 7, wherein the polyamide resin is nylon 6.   A method for producing a polyamide resin film according to any one of claims 1 to 8, wherein the polyamide resin film is produced by a simultaneous biaxial stretching method.

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