JP2009138087A - Polyamide-based resin film and manufacturing method of it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly practical polyamide-based resin film having good film passage characteristics in a heating process during post-processing over the overall length without respect to a condition of the post-processing, and hardly causing a difference in a shrinkage factor between the front and back sides of a bag when the bag is made by half-folding of the film. <P>SOLUTION: In this polyamide-based resin film, a difference Δn<SB>ab</SB>between a refractive index in the direction forming an angle of 45° with the film winding direction and that in the direction forming an angle of 90° with the direction at 45° to the film winding direction is not less than 0.003 and not more than 0.013, and a difference between a maximum value and a minimum value of HS160 (heat shrinkage at 160°C) in the width direction is regulated to be not more than 0.15%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyamide resin film, and particularly relates to a polyamide resin film having excellent processing characteristics.

  Biaxially oriented polyamide resin films are widely used mainly as packaging materials because of their excellent transparency, mechanical properties, gas barrier properties, impact resistance, and pinhole resistance. In particular, contents that require excellent impact resistance and pinhole resistance are used for so-called heavy bags, and they have been used mainly for bags larger than conventional bags such as rice bags. . This large bag is about 30 cm wide and about 60 cm long. As such a bag, a biaxially oriented polyamide resin film is usually used as a base film, and various heat-sealing sealants (polyethylene, polypropylene, etc.) are laminated, and then folded and three sides are heat-sealed. A so-called three-side sealed bag is generally used. Usually, foods and other contents are often automatically filled immediately after bag making, but biaxially oriented polyamide resin films have poor dimensional stability compared to biaxially oriented polyester resin films, and are heated into bags. Since the curl phenomenon occurs, the automatic filling device cannot accurately grasp the bag to open the bag mouth, and there is a problem that a content such as food leaks. Such a phenomenon appears remarkably in the sequential biaxial stretching method in which the film is stretched in the longitudinal direction and then stretched in the transverse direction, and such a phenomenon is more likely to occur at the end of the film. In the case of a large three-side sealed bag, the film edge and the part close to the center will be cut in half, so there is a difference in shrinkage in the width direction of the film. Curling occurs because of different dimensions.

  When creating a biaxially stretched film, the straight line drawn with an oil-based felt pen placed at right angles to the running direction of the sheet after the longitudinal stretching or the unstretched sheet stage before the transverse stretching becomes a bow shape (boeing line) The phenomenon observed in (Boeing phenomenon) is known. In order to make the physical properties in the width direction of the film uniform with respect to such a problem, as a method of manufacturing a film with suppressed bowing, for example, the heat setting process is divided into a first stage and a second stage. A method of providing a roll (Patent Document 1), a method of providing a transition for adjusting the temperature between the transverse stretching process and the heat treatment process by simultaneous biaxial stretching (Patent Document 2), and a lateral stretching process by simultaneous biaxial stretching. There is known a method (Patent Document 3) in which the temperature is gradually raised from the heat treatment step to the relaxation step and the maximum temperature is reached in the relaxation step. However, although these methods apparently reduce the distortion of the bowing line, they are not appropriate evaluations for reducing the substantial distortion of the physical properties of the film. Although a certain degree of correlation was observed between the apparent bowing line and the substantial physical property distortion, it was insufficient to prevent the curling phenomenon of the bag.

  As a method for reducing the distortion of the film, the non-oriented polyamide film is stretched in the machine direction (flow direction), relaxed by several percent, and then stretched at a draw ratio of 125% or less with respect to the draw ratio in the machine direction. A method of stretching in the direction (perpendicular to the flow direction) and further providing a preheating temperature of 80 ° C. or lower and a two-stage heat setting step is described (Patent Document 4). By doing so, the boil shrinkage rate is 3% or less in all directions, and it is said that a film having good flatness of the film and having little dimensional change during humidification can be obtained. However, with this method, the shrinkage difference in the width direction still remains even when each shrinkage rate becomes small, and there is a problem that trouble occurs due to the shrinkage difference because the temperature is raised at the time of high-speed processing. .

  In addition, as a method of reducing the physical property difference in the width direction, when stretching in the longitudinal direction, giving a temperature distribution to the film temperature at the end, then laterally stretching, suppressing the bowing phenomenon of the film when heat-fixed, As a result, a method for reducing the oblique difference in boil shrinkage is described. (Patent Document 5) However, this also does not solve the phenomenon that the difference in contraction rate in the vertical direction differs in the width direction.

  Also, in the process of longitudinally stretching a non-oriented unstretched film and then laterally stretching to produce a film, both ends of the stretched film are released from the tenter clip after completion of the heat treatment and relaxation treatment after the transverse stretching. Describes a method of performing reheat treatment by adjusting tension, treatment temperature, and wind speed using a floating heat treatment apparatus that blows hot air on the surface (Patent Document 6). However, even with this method, the vertical heat shrinkage difference in the width direction cannot be reduced, and there is a problem that the length is different on the front and back sides on one side of the bag when processed at high speed or a large three-side sealed bag. there were.

Japanese Unexamined Patent Publication No. 7-108598 JP 10-44230 A Japanese Patent Laid-Open No. 10-235730 JP 7-256750 A JP 2002-172695 A Japanese Patent Laid-Open No. 10-296853

  Therefore, regardless of the width of the mill roll, a method for reducing the difference in the heat shrinkage rate in the width direction of the film (the heat shrinkage rate in the longitudinal direction of the film) in order to improve the film passability in the post-processing step In the heat fixing process of the film, the applicant puts a continuous shielding plate on a plenum duct (hot air outlet) arranged at regular intervals with respect to the film traveling direction, and the width of the shielding plate By gradually expanding the film toward the film traveling direction side, the temperature in the width direction of the film is increased from the central part to the end part, and the relaxation amount at the end part approaches the relaxation amount at the central part. It has been proposed (Patent Document 7).

JP 2001-138462 A

  In the future, it is predicted that the line speed of post-processing will be improved from the viewpoint of productivity improvement, and it is considered that a film that can be suitably used even in high-temperature post-processing is required. However, the method of simply covering the plenum duct (hot air blowing portion) with a continuous shielding plate in the heat setting process increases the temperature hunting in the heat setting zone, so a long film of 1,000 m or more is required. When manufacturing (mill roll), a portion having poor permeability (that is, a portion having a large difference in thermal shrinkage in the width direction of the film) was formed. Therefore, the present invention eliminates such problems and provides a highly practical polyamide-based resin film that has good film permeability in the thermal process during post-processing over the entire roll length regardless of post-processing conditions. There is to do. In addition, the object of the present invention is that the film permeability in the heat treatment step during post-processing is very good over the entire length of the roll, and there is little difference in shrinkage between the front and back of one side of the half-cut bag. It is an object of the present invention to provide a production method capable of producing a polyamide-based resin film free from the problem at low cost and easily.

Among the present inventions, the structure of the first invention is that the refractive index in the direction forming an angle of 45 degrees with the winding direction of the polyamide resin film and the refractive index in the direction forming an angle of 135 degrees with the winding direction of the film. Δn _ab is a polyad-based resin film having a difference of 0.003 or more and 0.013 or less, and satisfies the following requirements (1) to (2).
(1) About the film whose length of the width direction of a film is 80 cm or more, about 5 samples cut out from the center part in the width direction of the film which divided | segmented into 5 evenly in the film width direction, and was divided into 10 at 160 degreeC. When HS160, which is the heat shrinkage rate in the film winding direction when heated for a minute, is determined, the difference between the maximum and minimum values of HS160 is 0.15% or less. (2) The five samples HS160 is 0.5% or more and 2.0% or less in all. The configuration of the second invention is characterized in that the polyamide-based resin film has a thickness of 5 μm or more and 100 μm or less.
Moreover, the structure of 3rd invention is a manufacturing method for manufacturing the said polyamide-type resin film, Comprising: The film-forming process which forms an unstretched sheet | seat by melt-extruding raw material resin from an extruder, The film A biaxial stretching step of biaxially stretching the unstretched sheet obtained in the forming step in the longitudinal direction and the transverse direction, and a heat fixing step of heat fixing the film after biaxial stretching, It is to be performed in a heat fixing device that satisfies the following requirements (3) to (5).
(3) A plurality of wide plenum ducts for blowing out hot air are arranged vertically opposite to the film traveling direction. (4) Shielding for shielding hot air outlets from the plurality of plenum ducts. (5) The dimension of each shielding plate in the traveling direction of the film is adjusted to be substantially the same as the dimension of the outlet of each plenum duct in the traveling direction of the film. The dimension in the width direction of the film is adjusted so as to become gradually longer with respect to the traveling direction of the film. The configuration of the fourth aspect of the invention is that the biaxial stretching step is performed after the film is stretched in the longitudinal direction. In addition to extending in the direction, an intermediate zone in which wind blowing is not performed is provided between the zone in which the transverse stretching is performed and the heat setting device.
According to a fifth aspect of the invention, the heat setting device is divided into a plurality of heat setting zones, and the product of the temperature difference and the wind speed difference between adjacent heat setting zones is 250. It exists in setting so that it may become below ° C * m / s.

  The polyamide-based resin film of the present invention is suitably used for applications in which the content is so-called water. A bag made of a film that has been subjected to a laminating process, such as a bag for retort food, is filled with the contents, and boil sterilization or retort sterilization is performed for sterilization. Such a retort food bag usually uses a biaxially oriented polyamide resin film as a base film, and after laminating various sealants (polyethylene, polypropylene, etc.) having heat-sealing properties, it is folded in half and 3 sides are formed. A heat-sealed so-called three-side sealed bag or a bag on which label printing has been applied is used, and is particularly suitable for such applications.

  The polyamide-based resin constituting the polyamide-based resin film of the present invention is mainly composed of polyamide, and examples of the polyamide include polyamides obtained by polycondensation of lactams having three or more members and ω-amino acids. Examples thereof include polyamides obtained by polycondensation and polyamides obtained by polycondensation of dibasic acid and diamine.

  Specific examples of lactams having 3 or more ring members used herein include ε-caprolactam, enantolactam, capryllactam, lauryllactam, etc .; specific examples of ω-amino acids include 6-aminocaproic acid and 7-aminoheptanoic acid , 9-aminononanoic acid, 11-aminoundecanoic acid, etc .; specific examples of dibasic acids include adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadionic acid, hexadecadione Acids, eicosandioic acid, eicosadienedioic acid, 2,2,4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, xylylenedicarboxylic acid, etc .; specific examples of diamines , Ethylenediamine, trimethylenediamine, tetramethylenediamine , Hexamethylenediamine, pentamethylenediamine, undecamethylenediamine, 2,2,4 (or 2,4,4) -trimethylhexamethylenediamine, cyclohexanediamine, bis- (4,4′-aminocyclohexyl) methane, And metaxylylenediamine.

  Further, polymers obtained by polycondensation of these or copolymers thereof include nylon 6, nylon 7, nylon 11, nylon 12, nylon 6,6, nylon 6,9, nylon 6,11, nylon 6・ 12, Nylon 6 ・ T, Nylon 6 ・ I, Nylon MXD ・ 6, Nylon 6/6 ・ 6, Nylon 6/12, Nylon 6/6 ・ T, Nylon 6/6 ・ I, Nylon 6 / MXD ・ 6 Etc. are exemplified.

  When nylon-6 is used as the polyamide resin of the present invention, the relative viscosity (RV) of the raw material nylon-6 is preferably in the range of 2.4 to 3.3. When the relative viscosity of the nylon-6 raw material is 2.4 or less, the degree of polymerization is lowered, and the bending resistance and the drop bag resistance are not preferable. On the other hand, if the relative viscosity exceeds 3.3, it is not preferable because the filtration pressure becomes too large and high-precision filtration becomes difficult. In addition, RV of a resin raw material is calculated | required with the following methods, for example.

[Relative viscosity (RV)]
A resin solution obtained by dissolving 0.25 g of a polyamide resin or a polyamide resin composition in 25 ml of 96% sulfuric acid as a solvent was used as a sample solution. 10 ml of this sample solution was measured at 20 ° C. using an Ostwald viscosity tube to measure the drop time (seconds) of the solvent and the sample solution. The RV value obtained by the following formula was used as the relative viscosity.
RV = t / t0 t0: solvent dropping time (seconds)
t: Sample solution drop time (seconds)

Further, when nylon-6 is used as the polyamide-based resin of the present invention, it is desirable that the raw material (including the recycled raw material) before being charged into the extruder does not contain foreign matters. At the time of melt extrusion, high-precision filtration is performed using a filter medium having a filtration particle size (initial filtration efficiency of 95%) of 30 μm or less, and 10 or less foreign matters having a diameter of 50 μm or more per 1 m ^{2 of} film after film formation. It is preferable to adjust so that. Note that the number of foreign substances in the raw material is obtained by the following method, for example.

[Number of foreign objects]
An enlarged image of the melted raw material chip is taken using a phase contrast microscope and a CCD camera, and the number of foreign matters is counted using an image processing apparatus.

[Δn _ab ]
The polyamide-based resin film of the present invention was wound with Δn _{ab in} the width direction of the mill roll once manufactured to a wide width (that is, with a refractive index in a direction forming an angle of 45 degrees with the winding direction of the wound film). The difference (absolute value) between the film winding direction and the refractive index in the direction forming an angle of 135 degrees is limited to 0.003 or more and 0.013 or less in all regions. That is, in the film where Δn _ab is less than 0.003, the above-mentioned problem of “strain (that is, physical property difference in the width direction)” does not occur. Further, in a film distorted so that Δn _ab exceeds 0.013, it is difficult to adjust the difference in heat shrinkage rate so as to satisfy the requirements of the present invention.

[HS160]
Moreover, the polyamide-type resin film of this invention is 160 about five film samples cut out from each cutout part when a sample cutout part is set by the method mentioned later when the sample cutout part is set by the method mentioned later. HS160 which is a heat shrinkage rate in the film winding direction when heated at 10 ° C. for 10 minutes is obtained, and the difference between the maximum value and the minimum value needs to be 0.15% or less.

When the difference between the maximum value and the minimum value of HS160 is 0.15% or less, the film can be easily passed in post-processing, which is preferable. Further, the difference between the maximum value and the minimum value of HS 160 is more preferably 0.12% or less, and particularly preferably 0.10% or less. In addition, although the difference between the maximum value and the minimum value of HS150 in each cutout portion is preferably as low as possible, 0.00% is considered to be the lower limit in design.

The film sample used for the measurement of the heat shrinkage rate is cut out from five cut-out portions provided by the following procedure.
(1) A film having a width direction length of 80 cm or more and Δn _ab of 0.003 or more and 0.013 or less is equally divided into five.
(2) A cutout portion is provided at the center in the width direction for each of the five divided films.
(3) A sample film having a width of 20 mm and a length of 250 mm is cut out from each cutout portion along the film winding direction, and five film samples are cut out.

  Furthermore, the polyamide-type resin film of this invention is a film winding direction when it heats for 10 minutes at 160 degreeC about five film samples cut out from each cut-out part when a sample cut-out part is set by an above-described method. When HS160, which is a heat shrinkage rate, is obtained, all samples must have HS160 of 0.5% or more and 2.0% or less.

  It is preferable that HS160 of all the samples is 2.0% or less because the film passability in post-processing is improved. Moreover, the value of HS150 of the film sample cut out from each cut-out part is more preferably 1.5% or less, and particularly preferably 1.2% or less. In addition, although the value of HS150 of the film sample cut out from each cut-out part is so preferable that it is low, 0.5% is considered to be a minimum from the point of productivity.

  The polyamide-based resin film of the present invention is obtained by subjecting an unstretched film (unstretched laminated film or unstretched laminated sheet) obtained by melting and extruding a polyamide-based resin chip as a raw material to a longitudinal direction (longitudinal direction) and a lateral method (width). Direction), and heat-fixed by a method described later.

  The polyamide resin film of the present invention is usually laminated with other materials as described above, but as other materials to be laminated, the most common polyolefin film such as polyethylene or polypropylene is used. In addition, various resin films made of polyester resin, acrylic resin, polycarbonate resin, polyvinyl resin, urethane resin, etc. can be used, and further laminated with metal foil or metal vapor deposition film if necessary. Is also possible.

  As a method for obtaining an unstretched sheet, after adjusting the moisture content of the polyamide resin pellets containing fine particles for imparting slipperiness to 0.08 to 1.02%, the moisture is supplied to an extruder, and about 270 A method of melt-extruding into a sheet form at 0 ° C. and cooling and solidifying the molten sheet with a cooling roll can be suitably employed.

  In addition, a well-known method can be applied to rapidly cool an unstretched sheet while bringing the sheet-like melt into close contact with the rotary cooling drum. For example, a method of using an air knife on the sheet-like melt or an electrostatic charge can be applied. A method of imprinting is preferably applicable. In those methods, the latter is preferably used.

  As a method of cooling the air surface of the sheet-like material, a known method can be applied. For example, a method of bringing the sheet surface into contact with a cooling liquid in the tank, a liquid evaporating with a spray nozzle on the sheet air surface You may use together the method of apply | coating, and the method of spraying a high-speed airflow and cooling. The unstretched sheet thus obtained is stretched in the biaxial direction to obtain a film.

  As a method of stretching the film in the biaxial direction, the obtained unstretched sheet is stretched in the longitudinal direction by a roll or a tenter type stretching machine, and then in a direction (width direction) orthogonal to the first-stage stretching direction. The method of extending | stretching can be mentioned. The stretching temperature in the longitudinal direction is 45 to 70 ° C., and the stretching ratio in the longitudinal direction is 2.5 to 4.0 times, preferably 3.0 to 3.6 times. If the stretching temperature in the longitudinal direction is less than 45 ° C., the film tends to break and is not preferable. Moreover, since it will worsen the thickness spot of the obtained film when it exceeds 70 degreeC, it is unpreferable. When the draw ratio in the longitudinal direction is less than 2.5 times, the flatness of the obtained film is deteriorated, which is not preferable. On the other hand, if it exceeds 4.0 times, the orientation in the longitudinal direction becomes strong, and the frequency of fracture increases in stretching in the transverse direction, which is not preferable.

  In the case of stretching in the width direction, the stretching temperature needs to be 80 to 210 ° C, preferably 100 to 200 ° C. If the stretching temperature in the width direction is less than 80 ° C., the film tends to break, which is not preferable. Moreover, when it exceeds 210 degreeC, since the uneven thickness of the obtained film worsens, it is not preferable. The draw ratio in the width direction is 3.0 to 5.0 times, preferably 3.5 to 4.5 times. If the draw ratio in the width direction is less than 3.0 times, the thickness unevenness of the obtained film is deteriorated, which is not preferable. If the draw ratio in the width direction exceeds 5.0 times, the frequency of breaking increases in the drawing, which is not preferable.

  Subsequently, heat setting is performed. The temperature of the heat setting treatment step is preferably 180 ° C. or higher and 230 ° C. or lower. If the temperature of the heat setting treatment is less than 180 ° C., the absolute value of the heat shrinkage rate is increased, which is not preferable. On the other hand, if the temperature of the heat setting treatment exceeds 230 ° C., the film tends to yellow or mechanical strength tends to be weak, and the frequency of breakage increases, which is not preferable. A suitable heat setting method will be described later.

  It is effective to control the heat shrinkage rate, particularly the heat shrinkage rate in the width direction, by narrowing the guide rail of the gripping tool by the heat setting process. The temperature for the relaxation treatment can be selected in the range from the heat setting treatment temperature to the glass transition temperature Tg of the polyamide resin film, and is preferably (heat setting treatment temperature) -10 ° C. to Tg + 10 ° C. The width relaxation rate is preferably 1 to 10%. If it is less than 1%, the effect is small, and if it exceeds 10%, the flatness of the film deteriorates or the film flutters in the tenter, which is not preferable.

  Here, although the method of extending | stretching to the width direction after extending | stretching first to a longitudinal direction was described, the extending | stretching order may be reverse. In addition, the longitudinal stretching and the lateral stretching may be performed in one stage, or may be performed in two or more stages. In addition, as described above, in addition to the method of sequentially biaxially stretching an unstretched film, a simultaneous biaxial stretching method in which an unstretched film is simultaneously stretched in the machine direction and the transverse direction can be employed. However, in order to satisfy the characteristics of the present invention, it is important to take optimum temperature conditions and longitudinal and lateral draw ratios, and it is sufficient that the finally obtained film characteristics satisfy the requirements of the present invention.

  Moreover, in order to give functionality to a film, it is good also as a polyamide-type resin film which has a multilayer structure of two or more layers. When the surface on which the slippery layer or the easy adhesion layer is applied is the A layer, the opposite surface is the B layer, and the other surface is the C layer, the layer structure in the film thickness direction is A / B, A / C / B or Configurations such as A / C / E / D / B are conceivable. The layers A to E may be made of the same material or different materials.

  The thickness of the film which comprises the polyamide-type resin film of this invention is not specifically limited. However, when used for food packaging applications, the thickness is preferably 5 μm or more and 100 μm or less. Further, the upper limit of the thickness of the film is more preferably 70 μm or less, further preferably 50 μm or less, still more preferably 40 μm or less, and particularly preferably 30 μm or less.

  The width of the polyamide resin film of the present invention is not particularly limited, but from the viewpoint of ease of handling, the lower limit of the width is preferably 0.35 m or more, and is 0.50 m or more. More preferred. On the other hand, the upper limit of the width is preferably 2.5 m or less, more preferably 2.0 m or less, and further preferably 1.5 m or less. In addition, the length of the film is not particularly limited, but the lower limit of the length is preferably 500 m or more and more preferably 1,000 m or more from the viewpoint of ease of winding and handling. On the other hand, the upper limit of the length is preferably 2,5000 m or less, more preferably 20,000 m or less, and further preferably 15,000 m or less. In addition, when a film thickness is about 15 micrometers, it is especially preferable in it being 12000 m or less. In addition, as the winding core, usually, paper of 3 inches, 6 inches, 8 inches, etc., a plastic core or a metal core can be used.

  The polyamide-based resin film of the present invention may be a single layer or a film having a laminated structure of two or more layers, and post-processed on one side or both sides of a biaxially stretched polyamide-based resin film that does not contain fine particles with emphasis on transparency. There is no problem even if various coatings are applied at the time of film formation for the purpose of improving the adhesion during the process and the purpose of improving the slipperiness.

  Moreover, in the polyamide-type resin film which comprises the film of this invention, microparticles | fine-particles can be added as needed. Examples of the fine particles added at that time include known inorganic fine particles and organic fine particles. Furthermore, in the resin forming the film, various additives as necessary, for example, waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducing agents, heat stabilizers, coloring pigments, An anti-coloring agent, an ultraviolet absorber and the like can be added. It is preferable to add fine particles to the polyamide resin in the present invention to improve the workability (slidability) of the polyamide resin film. Any fine particles can be selected. Examples of inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of the organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles. The average particle diameter of the fine particles can be appropriately selected as necessary within a range of 0.05 to 2.0 μm.

  As a method of blending the above-mentioned particles into the polyamide resin film, for example, it can be added at any stage of producing the polyamide resin, but preferably the stage of initiating the amide bond or the stage after completion of the amide bond reaction It may be added as a slurry dispersed in water to proceed the polycondensation reaction. Also, a method of blending a slurry of particles dispersed in water with a vented kneading extruder and a polyamide resin raw material, or a blending of dried particles and a polyamide resin raw material using a kneading extruder. It can be performed by a method or the like.

  Furthermore, the polyamide resin film constituting the film of the present invention is not subject to any surface activation treatment by methods such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, fire treatment, and coating treatment. The surface treatment can be performed on one or both of the surface-modified layer surface and the opposite surface.

  Next, the preferable manufacturing method for obtaining the polyamide-type resin film of this invention is demonstrated.

  Usually, the heat setting process of the stretched film is often carried out in a heat setting device in which a plurality of plenum ducts having a long hot air outlet are arranged perpendicular to the longitudinal direction. And in the heat fixing device provided with such a plenum duct, in order to improve the heating efficiency, the air in the heat fixing device is sucked by the circulation fan attached to the heat fixing device, and then sucked. By adjusting the temperature of the air and exhausting it again from the hot air outlet of the plenum duct, "hot air circulation" is performed: "hot air blowing-> suction by a circulation fan-> temperature adjustment of sucked air-> hot air blowing" Is called.

  Further, as described above, the difference in heat shrinkage rate in the film width direction (difference between the maximum value and the minimum value of HS160) cannot promote relaxation in the longitudinal direction at the end of the film in the width direction at the time of heat fixing. To occur. As shown in FIG. 1, a method of covering a central portion of the hot air outlets 2, 2,... Of the plenum ducts 3, 3,. In the case of a short film, the passability when the heat setting treatment in the post-processing is performed at a low temperature is improved, but the passability in the long film and the heat setting in the post-processing are improved. The passability when the treatment is performed at a high temperature is not improved at all.

  When the inventors attached a continuous large shielding plate to the hot air outlet of the plenum duct, why "passability in a long film" or "when heat fixing treatment in post-processing is performed at a high temperature In order to ascertain whether the “passability of” is not improved, the phenomenon in the heat setting device was analyzed in detail. As a result, when a continuous large shielding plate spanning a plurality of plenum ducts is put on the hot air outlet of the plenum duct, the flow of hot air blown from the hot air outlet of the plenum duct is significantly limited by the shielding plate, It has been found that a temperature hunting phenomenon occurs in the heat fixing device due to the fact that the above-mentioned "hot air circulation" is not performed smoothly.

The present inventors have described that the above-mentioned “temperature hunting phenomenon” induces insufficient thermal relaxation at the edge of the film, such as “passability in a long film” and “heat setting treatment in post-processing. It was speculated that it may have an adverse effect on the “passability when it is carried out at a high temperature”. Furthermore, the present inventors controlled the conditions such as the temperature and the air volume of the heat fixing device, and improved the coating method when covering the hot air outlet of the plenum duct with a shielding plate, thereby making the “hot air” described above. ”Circulation” can be performed smoothly, and “temperature hunting phenomenon” can be suppressed. As a result, “passability in long films” and “heat setting in post-processing are performed at high temperatures” It was speculated that it would be possible to improve the "passability when And, as a result of trial and error to grasp the relationship between the temperature, the air flow condition of the heat setting device, the covering mode of the shielding plate, and the film permeability in the post-processing, the following (1) By taking measures, there was a tendency that “passability in a long film” and “passability when heat-setting treatment in post-processing was performed at a high temperature” were improved. And based on the knowledge, as a result of further trial and error, the present inventors have taken the following means (1) and then taken the following means (2) and (3). The inventors have found that it is possible to obtain a film having good permeability, and have come up with the present invention.
(1) Adjustment of temperature and air volume of plenum duct in heat fixing device (2) Adjustment of shut-off condition of hot air outlet of plenum duct in heat fixing device (3) Heat cutoff between stretching zone and heat fixing device Each of the above-described means will be described sequentially.

(1) Adjustment of temperature and air volume of plenum duct in heat setting device In the production of the film of the present invention, the product of the temperature difference and the wind speed difference between adjacent heat setting zones of the heat setting device is 250. It is essential to adjust the temperature and air volume of the hot air blown out from each plenum duct so that it is not higher than ° C. · m / s. For example, when the heat setting device is divided into first to third heat setting zones, the product of the temperature difference and the wind speed difference between the first zone and the second zone, and between the second zone and the third zone. Both the product of the temperature difference and the wind speed difference need to be adjusted to be 250 ° C. · m / s or less. In such a case, a discontinuous shielding plate is attached to the hot air outlet of the plenum duct as described later by adjusting the temperature and air volume of the hot air blown from the hot air outlet of the plenum duct in each heat fixing zone. In addition, “circulation of hot air” in the heat setting device is executed smoothly, and “temperature hunting phenomenon” is effectively suppressed. However, it becomes possible to obtain a long film having a good length.

  When the product of the temperature difference and the wind speed difference between adjacent heat setting zones exceeds 250 ° C. · m / s (for example, the temperature difference between adjacent heat setting zones is set to 30 ° C. In addition, if the difference in wind speed between adjacent heat setting zones is set to 10 m / s), the “hot air circulation” in the heat setting device will not be performed smoothly, effectively preventing the “temperature hunting phenomenon”. Since it becomes impossible to suppress, it is not preferable. In addition, when the product of the temperature difference and the wind speed difference between the adjacent heat setting zones exceeds 250 ° C. · m / s, as an accompanying flow caused by the passage of the film, from the upstream heat setting zone to the downstream heat setting zone And the temperature difference between the flowing air becomes large, which adversely affects the temperature stability in the width direction of the downstream heat setting zone. The product of the temperature difference and the wind speed difference is preferably 200 ° C. · m / s or less, and more preferably 150 ° C. · m / s or less.

  When the product of the temperature difference and the wind speed difference between adjacent heat setting zones exceeds 250 ° C. · m / s (for example, the temperature difference between adjacent heat setting zones is set to 30 ° C. In addition, if the difference in wind speed between adjacent heat setting zones is set to 10 m / s), the “hot air circulation” in the heat setting device will not be performed smoothly, effectively preventing the “temperature hunting phenomenon”. Since it becomes impossible to suppress, it is not preferable. In addition, when the product of the temperature difference and the wind speed difference between the adjacent heat setting zones exceeds 250 ° C. · m / s, as an accompanying flow caused by the passage of the film, from the upstream heat setting zone to the downstream heat setting zone And the temperature difference between the flowing air becomes large, which adversely affects the temperature stability in the width direction of the downstream heat setting zone. The product of the temperature difference and the wind speed difference is preferably 200 ° C. · m / s or less, and more preferably 150 ° C. · m / s or less.

(2) Adjustment of plenum duct blocking condition in heat setting device In the production of the film of the present invention, as described above, the temperature and amount of hot air blown from the hot air outlet of the plenum duct were adjusted in each heat setting zone. In the above, instead of attaching a large shielding plate across a plurality of plenum ducts arranged in the heat fixing device, as shown in FIG. 2, hot air outlets (nozzles) 2, 2 of the individual plenum ducts 3, 3,. It is necessary to attach rod-shaped shielding plates S, S ... so as to shield them one by one. In addition, when attaching a rod-shaped shielding plate to each plenum duct, the length of the shielding plate is gradually increased from the inlet to the outlet of the heat fixing device instead of attaching the same length of shielding plate to each plenum duct. It is preferable to lengthen the length (see FIG. 1). The material of the shielding plate is preferably the same material as the plenum duct in consideration of the thermal expansion in the heat fixing device, but can withstand the temperature of the heat fixing device and stain the film, There is no particular limitation as long as the film is not adhered.

(3) Blocking of heating between the stretching zone and the heat setting device (installation of an intermediate zone)
A biaxially stretched polyamide resin film is usually manufactured by being subjected to heat-setting treatment after being longitudinally and laterally stretched as described above, but in the production of the film of the present invention, it is longitudinally and laterally stretched. It is preferable to install an intermediate zone that does not blow active hot air between the zone and the heat-fixing device to be heat-set, and to completely shut off the heating between the stretching zone and the heat-fixing device. . More specifically, the stretching zone and the heat setting device are adjusted to the same conditions as in the film production, and when the strip-shaped paper piece is hung between the stretching zone and the heat setting device in that state, the piece of paper is It is preferred to block the hot air from the stretching zone and the heat setting device so that it hangs almost completely in the vertical direction. In addition, the intermediate zone which does not perform such hot air blowing may be surrounded by a housing, or may be provided so that a continuously manufactured film is exposed. Insufficient blocking of the hot air in the intermediate zone is not preferable because the shielding effect of the shielding plate in the heat fixing device is insufficient, and good film permeability during post-processing cannot be obtained.

  As described above, by adopting the above methods (1) to (3), the “hot air circulation” in the heat fixing device can be smoothly executed, and the “temperature hunting phenomenon” can be suppressed. As a result, it is possible to sufficiently promote relaxation in the longitudinal direction at the edge of the width direction, such as “passability in a long film” and “passability when heat setting treatment in post-processing is performed at a high temperature”. Can be improved. In the above description, the method of suppressing the “temperature hunting phenomenon” by smoothly executing “circulation of hot air” in the heat fixing device in which the plenum duct is installed. The above description discloses the technical idea of how the film of the present invention can be obtained by applying thermal energy to the film at the production level. The film of the present invention can be easily obtained by a different method from that described above. For example, instead of providing a shielding plate, an infrared heater may be used to increase the temperature in the film width direction from the center to the end. In other words, even with another type of heat fixing device, the "circulation of hot air" is smoothly executed to suppress the "temperature hunting phenomenon" and then sufficiently relaxed in the longitudinal direction at the edge of the width direction. By applying sufficient heat energy to the film, it is possible to improve the “passability in a long film” and the “passability when heat-setting treatment in post-processing is performed at a high temperature” like the film of the present invention. Film can be obtained.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the embodiments of the examples, and can be appropriately changed without departing from the spirit of the present invention. . In addition, the evaluation method of a film characteristic is as follows.

1. Δn _ab
Film test pieces were sampled from positions within 50 mm and center positions from both end edges parallel to the film winding direction of the obtained film. After leaving the film test piece in an atmosphere of 23 ° C. and 65% RH for 2 hours or more, using an “Abbe refractometer 4T type” manufactured by Atago Co., Ltd., an angle of 45 degrees with the winding direction of the wound film Refractive index (n _a ) in the direction of forming a film, and refraction in _a direction that forms an angle of 135 degrees with the winding direction of the wound film (that is, a direction that forms an angle of 90 degrees with the 45-degree direction described above) Each rate (n _b ) was measured. The calculated absolute value of the difference between the two refractive index thereof as [Delta] n _ab. The absolute value of the difference between these two refractive indexes is Δn _ab, and Δn _ab = | n _a −n _b | It was confirmed that Δn _ab at both ends and the center of the film roll was 0.015 or more and 0.060 or less, and the largest value was designated as Δn _ab in the table. In the present invention, the winding direction of the film is also referred to as the longitudinal direction or the longitudinal direction of the film.

2. The heat shrinkage rate of the film From the position where the above Δn _ab in the width direction of the film includes 0.003 or more and 0.013 or less from the position 80 cm or more apart, the width direction is equally divided into five, and in the center of the width direction. A cutting part is provided, and a sample having a width of 20 mm and a length of 250 mm in the longitudinal direction is cut out. After seasoning each sample for 30 minutes in an atmosphere of 23 ° C. and 50%, HS160, which is the thermal shrinkage in the film winding direction when heated in the longitudinal direction at 160 ° C. for 10 minutes, is determined. After the seasoning, the specimens having a width of 20 mm and a length of 250 mm cut out were marked with markings at intervals of 200 mm, placed in a heating oven adjusted to 160 ° C., and heated for 10 minutes. After removal, the sample was seasoned at 23 ° C. and 50% atmosphere for 30 minutes, the film length was measured, and the thermal shrinkage rate of each film was measured. The difference between the maximum value and the minimum value was defined as the heat shrinkage rate difference.

3. Film passability Using a coater in which the distance between two rolls is 1,900 mm, the temperature is set to 100 ° C. or 160 ° C., the furnace tension is set to 100 N, and Δn _ab is 0.003 or more and 0.013 or less. Heat treatment was performed on the slit roll taken to include. Subsequently, in order to evaluate the flatness of the heat-treated film, the heat-treated film was passed between two horizontally arranged rolls having a roll interval of 2,000 mm under a tension of 98N. In addition, the iron bar was arrange | positioned so that the upper surface of an iron bar may be located in the center position between the rolls with this roll space | interval of 2,000 mm in the position below 30 mm from the common tangent of the horizontally arranged roll upper surface. When the film was allowed to pass through, it was marked as ◯ when the film was not in contact with the iron bar, and was marked as x when it was in contact with the iron bar. These steps were performed continuously, and it was visually confirmed whether or not the film contacted the iron bar.

4). Evaluation of wrinkles on bag seal part A film having a winding length of about 1,000 m, which is taken so that Δn _ab is 0.003 or more and 0.013 or less, is a urethane AC agent (“EL443” manufactured by Toyo Morton Co. ), A 15 μm thick LDPE (low density polyethylene) film was extruded at 315 ° C. using a single test laminator manufactured by Modern Machinery Co., Ltd., and a 40 μm thick LLDPE ( (Linear low density polyethylene) film was continuously laminated to obtain a laminate film having a three-layer structure composed of polyamide resin / LDPE / LLDPE. The laminate film wound up as a laminate film is folded in two parallel to the winding length direction using a test sealer manufactured by Seibu Machinery Co., Ltd., and continuously heat sealed at 150 ° C. at both ends of 20 mm each in the longitudinal direction. Then, 10 mm in the vertical direction was intermittently heat-sealed at intervals of 550 mm to obtain a semi-finished product having a width of 280 mm. This was cut in the winding length direction and both edges were cut so that the seal portion was 10 mm, and then cut at the boundary of the seal portion in the direction perpendicular to this to produce a three-side seal bag (seal width: 10 mm). . Ten of these three-side seal bags were sampled continuously from a distance of 2 m or more from the end of the film winding, and the seal portion in the longitudinal direction was observed to evaluate whether the seal portion was wrinkled.
◎: 10 wrinkle-free bags ○: 1-3 bags with slight wrinkles ×: 4 or more bags with slight wrinkles XX: 1 with clear wrinkles There are more than bags

[Example 1]
Nylon 6 (RV = 2.8) containing 0.35% by weight of silica having an average particle size of 0.7 μm (TEM method) as an additive and 0.1% by weight of ethylenebisstearylamide as a slip aid After the drying was adjusted so that the water content was 0.1% by weight, it was charged into a hopper immediately above the extruder and melted at a temperature of 270 degrees in the extruder. Further, when melting with an extruder, the molten resin was filtered with a filter material of a stainless sintered body (nominal filtration accuracy: 90% or more of particles having a size of 30 μm or more). Next, the melted resin is extruded as a sheet from a T-shaped die, wound around a casting drum whose surface is adjusted to 30 ° C. by using an electrostatic application casting method, and cooled and solidified to be unstretched with a thickness of about 175 μm. A polyamide sheet was obtained.

  Thereafter, the unstretched sheet described above is heated to 55 ° C. by a heated roll group, and thereafter, a continuous 3.1-fold stretching operation in the longitudinal direction is performed with a roll group having a peripheral speed difference, Next, the end of the uniaxially stretched film was gripped with a clip, led to a hot air zone heated at 130 ° C., and continuously stretched 4.0 times in the width direction. Furthermore, a heat setting process is performed at 215 ° C. by a method described later, a 6.7% transverse relaxation process is performed at 200 ° C., and the film is wound into a roll shape, thereby being biaxially oriented with a width of 3,300 mm and a thickness of about 15 μm. A polyamide film (mill roll) was obtained.

[Heat setting]
The heat setting process was performed by a heat setting apparatus having a structure as shown in FIG. The heat setting device is divided into four heat setting zones called first to fourth zones, and eight plenum ducts a to x are provided in the first to third zones, respectively. In addition, eight plenum ducts are provided. Each plenum duct is vertically installed at 400 mm intervals with respect to the film traveling direction so as to be perpendicular to the film traveling direction. And hot air is sprayed on the film extended | stretched from the hot air blowing outlet (nozzle) of those plenum ducts.

  In Example 1, discontinuous rod-shaped shielding plates S, S,... Were attached to the hot air outlets of 15 plenum ducts a to o in the manner shown in FIG. FIG. 4 shows a state where the heat fixing device having the shielding plates S, S,... Attached to the hot air outlets of the plenum ducts a to o is viewed from above, and each of the attached shielding plates S, S,. The center in the longitudinal direction is set so as to substantially coincide with the center of the width of the film passing through the heat fixing device. Further, the length of each shielding plate S, S... (The dimension in the width direction of the film to be manufactured) is adjusted so that it gradually becomes wider (that is, widens toward the end) from the inlet to the outlet of the heat fixing device. Has been. Table 2 shows the shielding ratio of the hot air outlets of each of the plenum ducts a to o (the shielded area of the hot air outlet by the shielding plate / the area of the hot air outlet). In addition, let the shielding aspect by the shielding board in Example 1 be "A aspect."

  In Example 1, the temperatures and wind speeds in the first to fourth zones of the heat setting device were adjusted as shown in Table 3. In addition, in the temperature conditions of the 1st-4th zone of the heat setting apparatus of Example 1, and the wind speed conditions, the product of the temperature difference between the adjacent heat setting zones and the wind speed difference is 250 ° C. · m / s or less. In addition, let the temperature of 1st-4th zone in Example 1, and wind speed conditions be "I conditions."

[Characteristic evaluation of film]
The film obtained as described above was evaluated for characteristics by the method described above. The evaluation results are shown in Table 4.

[Example 2]
Increase the melt extrusion amount by the extruder to increase the width of the unstretched film, and change the shielding plate attached to the hot air outlet of each plenum duct of the heat fixing device so as to have a shielding rate as shown in Table 2. Except for changing the temperature and wind speed of the first to fourth zones of the heat setting device as shown in Table 3, a mill roll was obtained by winding a film having a thickness of about 15 μm and a width of 5,300 mm in the same manner as in Example 1. . Thereafter, the characteristics of the film were evaluated by the method described above. The evaluation results are shown in Table 4. In addition, the shielding mode by the shielding plate in Example 2 is referred to as “B mode”, and the temperature and wind speed conditions in the first to fourth zones in Example 2 are referred to as “II conditions”.

[Example 3]
The thickness of the unstretched sheet is increased to about 280 μm by increasing the amount of melt extrusion by the extruder to change the film thickness after heat setting to about 25 μm, and the stretching operation in the longitudinal direction is stretched by 3.0 times. Except having changed into operation, it carried out similarly to Example 1, and obtained the mill roll which wound up the film of width about 3300mm about 25 micrometers in thickness. And the characteristic of a film and a film roll was evaluated using the slit roll in the same position as Example 1. The evaluation results are shown in Table 4.

[Comparative Example 1]
The heat fixation was carried out without attaching a shielding plate to the hot air outlet of each plenum duct, and the temperature and wind speed in the first to fourth zones of the heat fixation device were changed as shown in Table 3, and the same as in Example 1. Thus, a mill roll film of about 15 μm was obtained. The temperature and wind speed conditions in the first to fourth zones in Comparative Example 1 are referred to as “III conditions”. And the evaluation of the characteristic of a film and a film was performed using the slit roll in the same position as Example 1. The evaluation results are shown in Table 4.

[Comparative Example 2]
The heat fixation was carried out without attaching a shielding plate to the hot air outlet of each plenum duct, and the temperature and wind speed in the first to fourth zones of the heat fixation device were changed as shown in Table 3, and the same as in Example 2. Thus, a mill roll film of about 15 μm was obtained. The temperature and wind speed conditions in the first to fourth zones in Comparative Example 2 are referred to as “IV conditions”. And using the slit roll in the same position as Example 2, the characteristics of the film and the film were evaluated. The evaluation results are shown in Table 4.

[Comparative Example 3]
The heat fixation was carried out without attaching a shielding plate to the hot air outlet of each plenum duct, and the temperature and wind speed of the first to fourth zones of the heat fixation device were changed as shown in Table 3 in the same manner as in Example 3. Thus, a mill roll film of about 25 μm was obtained. The temperature and wind speed conditions in the first to fourth zones in Comparative Example 3 are defined as “III conditions”. And the evaluation of the characteristic of a film and a film was performed using the slit roll in the same position as Example 1. The evaluation results are shown in Table 4.

[Effects of Example Film]
From Table 4, the films of the examples all have a small difference in heat shrinkage rate across the width (that is, a difference in heat shrinkage rate), and also a small amount of fluctuation in the heat shrinkage rate in the longitudinal direction, which is passed during post-processing. It can be seen that the properties are good and suitable for post-processing. Furthermore, it is finished neatly without wrinkles on the seal when it is made into a bag. On the other hand, it can be seen that the film of the comparative example has a large difference in heat shrinkage ratio over the entire width and poor passability during post-processing, and that when it is made into a bag, the seal portion is wrinkled and not finished cleanly.

  Since the polyamide-based resin film of the present invention has excellent processing characteristics as described above, a heat treatment in a packaging film used for a large size bag or other post-processing is performed in a high temperature zone (about 160 ° C.). And can be suitably used as a processing film for a relatively long time (10 to 60 seconds).

It is explanatory drawing which shows the shielding aspect by the conventional shielding board (a shows the vertical cross section of a part of heat setting apparatus, b shows the state which attached the shielding board to the hot-air outlet of a plenum duct. It shows the state seen from above.) It is explanatory drawing which shows the shielding aspect by the shielding board in this invention. (A shows a vertical section of a part of the heat fixing device, and b shows a state where a shield plate is attached to the hot air outlet of the plenum duct as viewed from above.) It is explanatory drawing which shows the state which saw through the heat fixing apparatus used by the Example and the comparative example from the top. It is explanatory drawing which shows the shielding aspect by a shielding board.

Explanation of symbols

1. Heat fixing device,
2. Hot air outlet 3, ax, Plenum duct F, Film,
S .. Shielding plate A: Film winding direction Z1: First zone Z2: Second zone Z3: Third zone Z4: Fourth zone

Claims (5)

Δn _ab, which is the difference between the refractive index in the direction that forms an angle of 45 degrees with the winding direction of the polyamide resin film and the refractive index in the direction that forms an angle of 135 degrees with the winding direction of the film, is 0.003 or more. A polyamide-based resin film that is 013 or less and satisfies the following requirements (1) to (2):
(1) About the film whose length of the width direction of a film is 80 cm or more, about 5 samples cut out from the center part in the width direction of the film which divided | segmented into 5 evenly in the film width direction, and was divided into 10 at 160 degreeC. When HS160, which is the heat shrinkage rate in the film winding direction when heated for a minute, is determined, the difference between the maximum and minimum values of HS160 is 0.15% or less. (2) The five samples HS160 is 0.5% or more and 2.0% or less   The polyamide resin film according to claim 1, wherein the film has a thickness of 5 μm to 100 μm. A production method for producing a polyamide-based resin film according to claim 1 or 2, wherein a film forming step of forming an unstretched sheet by melt-extruding a raw material resin from an extruder, and the film A biaxial stretching step of biaxially stretching the unstretched sheet obtained in the forming step in the longitudinal direction and the transverse direction, and a heat fixing step of heat fixing the film after biaxial stretching, The manufacturing method of the polyamide-type resin film characterized by performing in the heat setting apparatus which satisfy | fills the following requirements (3)-(5).
(3) A plurality of wide plenum ducts for blowing out hot air are arranged vertically opposite to the film traveling direction. (4) Shielding for shielding hot air outlets from the plurality of plenum ducts. (5) The dimension of each shielding plate in the traveling direction of the film is adjusted to be substantially the same as the dimension of the outlet of each plenum duct in the traveling direction of the film. The dimension in the width direction of the film is adjusted so as to become gradually longer with respect to the film traveling direction.   In the biaxial stretching process, the film is stretched in the transverse direction after stretching the film in the longitudinal direction, and an intermediate zone that does not perform wind blowing is provided between the zone that performs the transverse stretching and the heat setting device. The manufacturing method of the polyamide-type resin film of Claim 3 characterized by these.   The heat setting device is divided into a plurality of heat setting zones, and the product of the temperature difference and the wind speed difference between adjacent heat setting zones is set to be 250 ° C. · m / s or less. The manufacturing method of the polyamide-type resin film of Claim 3 or Claim 4 characterized by the above-mentioned.

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