JP5041879B2 - Polyamide film and method for producing the same - Google Patents

Description

The present invention relates to a polyamide film and a method for producing the same, and more particularly to a polyamide film subjected to corona treatment on both sides and a method for producing the same.

  By activating the plastic film sheet surface to improve the adhesion (wetting) during coating of printing inks, release agents, adhesives, etc., as well as during deposition such as metal deposition Corona discharge treatment is widely known as a surface treatment means for plastic films for the purpose of effectively processing.

  On the other hand, polyamide films made of polyamide resin are excellent in mechanical properties, optical properties, thermal properties, gas barrier properties, toughness, etc., so they can be subjected to secondary processing such as printing, vapor deposition and coating, and sealant films. It is widely used mainly for packaging applications, particularly food packaging applications, such as other plastic films and laminated films laminated with metal foil.

  For example, in the case of a laminated film composed of a polyester film / polyamide film / sealant film used for boil and retort, a polyamide film used as an intermediate layer is preferably used with corona treatment on both sides. The

  According to a general plastic film manufacturing method, the corona treatment is performed between a step of simultaneously stretching or sequentially stretching an unstretched film and heat-setting, and then winding the film as a raw roll with a winder. The When corona treatment is performed on both surfaces, corona treatment is performed on one surface, and then corona treatment is performed on the other surface. The obtained raw fabric roll is transferred to a slitting process, cut into a desired width and length, and then shipped as a product roll.

  However, when the corona treatment is applied to both sides, the surfaces activated by the corona treatment come into contact with each other when wound as a roll, so the films are often blocked in the raw roll, and slits There may be a problem that it becomes impossible to unwind by processing.

  Such a defect is also found in a double-sided vapor deposition polypropylene film. As countermeasures, Patent Documents 1 and 2 disclose a polypropylene film having both surfaces subjected to corona treatment and improved blocking properties. Among them, in Patent Document 1, a protrusion having a specific diameter is formed on the film surface to suppress blocking. Moreover, in patent document 2, the reactivity is made low and the blocking is suppressed by adding the antioxidant which does not contain a carbonyl group.

However, in the case of a polyamide film or a polyester film containing a large number of functional groups, the effect is not sufficient even when the above-described improvements are applied.
JP 2001-2805 A JP 2002-234958 A

The present invention is to solve the above problems, the polyamide can be provided even polyamide film was subjected to corona treatment on both sides, without causing blocking after wound in winder, thus without hindrance slitting step film And it aims at providing the manufacturing method.

The inventor of the present invention has a corona-treated polyamide film on both sides, which is usually blocked by a roll having a width of 2000 mm or more, and is usually cut to about 500 mm to less than 2000 mm by a slit. Focusing on the fact that almost no blocking occurred in the product roll, the reason was estimated as follows.

  When manufacturing a wide film, it is usually difficult to make the film completely flat, and sagging described later occurs. When a film with slack is wound up, the tension varies in the width direction, and as a result, the winding hardness is partially increased. When the double-sided corona film is partially wound and wound in a state of increased hardness, blocking occurs.

  On the other hand, the product roll cut to a width of less than 2000 mm has a relatively small slack, a shorter winding length than the original fabric roll, and time has elapsed since the corona treatment was performed. It is considered that blocking is unlikely to occur due to such factors.

Therefore, as a result of intensive studies, the present inventor formed a polyamide film in a slender shape, and corona-treated on both sides, forming a non-treated portion at both ends in the width direction on at least one side of the film and winding it up. Thus, the inventors have found that the above-mentioned object can be achieved, and reached the present invention.

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

(1) A polyamide film having a width of 2000 mm to 5000 mm, corona treatment on both surfaces, and non-corona treatment portions on at least one side in the width direction.

(2) The polyamide film according to (1), wherein the amount of sag is 0.5 to 2.0.

(3) The polyamide film according to (1) or (2), wherein the wetting tension is 44 to 52 mN / m on both sides.

( 4 ) A method for producing a corona-treated polyamide film on both sides, characterized by forming corona-treated non-treated portions at both ends in the width direction on at least one side of a polyamide film having a width of 2000 mm to 5000 mm. A method for producing a polyamide film.

( 5 ) The method for producing a polyamide film according to ( 4 ), wherein the amount of sag of the polyamide film is 0.5 to 2.0.

( 6 ) The method for producing a polyamide film according to ( 4 ) or ( 5 ), wherein the wetting tension of the polyamide film is 44 to 52 mN / m on both sides.

According to the present invention, the polyamide film is formed to have a width of 2000 mm to 5000 mm, both surfaces are subjected to corona treatment, and at least one end of the corona treatment is formed at both ends in the width direction on one surface. Therefore, blocking with the raw roll is less likely to occur, and therefore a polyamide film suitable for medium use can be obtained by performing corona treatment on both sides.

Hereinafter, the present invention will be specifically described.
In the present invention, the polyamide film subjected to the corona treatment can be produced by a known method. For example, after extruding the molten polymer from a T-die, it is cooled with a casting roll to produce an unstretched sheet, which is simultaneously biaxially stretched or sequentially biaxially stretched. The stretched film is subjected to a short heat treatment at a temperature of around 200 ° C. in order to improve dimensional stability.

The width | variety of the polyamide film of this invention needs to be 2000 mm-5000 mm, Preferably it is 3000 mm-4500 mm. If the width of the polyamide film is less than 2000 mm, blocking is less likely to occur, but in industrial production, the degree of freedom for cutting to a desired width in the slitting process is low, resulting in poor productivity and high cost. On the other hand, when the width of the polyamide film exceeds 5000 mm, the stretching stress becomes too high, and the film is easily broken in the stretching process, and even if it can be stretched, the relative sag is increased, resulting in blocking.

  In the present invention, the film needs to be corona-treated on both sides. This is because the blocking problem does not occur when the corona treatment is not performed or the corona treatment is performed only on one side.

  The corona discharge device that can be used in the present invention includes a corona treatment roll around which a film is wound, and a corona discharge electrode provided facing a portion of the corona treatment roll around which the film is wound. The corona discharge electrode is attached to the torque tube and configured to receive a high-frequency AC power having a high frequency from an oscillator. And a corona discharge apparatus is installed in at least 2 places so that both surfaces of a film can be processed.

  The corona treatment roll has a structure in which a rubber layer is formed around the metal roll, and has a specific dielectric constant, withstand voltage, and heat resistance so that a uniform corona treatment can be applied to the film. ing.

In the present invention, it is necessary to create a non-corona-treated portion on at least one side of both end portions in the width direction of the polyamide film. It is preferable to create a non-corona-treated portion on both sides of both ends. Although the width | variety of a non-processed part is not specifically limited, 10 mm-100 mm are preferable and 20 mm-50 mm are more preferable. If the width of the non-treated part exceeds 100 mm, the part to be a product subjected to the double-sided corona treatment is reduced, and the production yield is deteriorated. When the width of the non-treated portion is less than 10 mm, blocking tends to occur at the end in the width direction of the film.

  In order to create an untreated portion, the electrode may be made shorter than the film width, or the portion corresponding to the end of the film in the electrode may be masked with an insulator. As insulators used for masking, synthetic products include various ceramics, glass, synthetic resins, synthetic rubbers, etc., and natural products include rubber materials, natural resins, oils and fats, petroleum substances (paraffin, wax, etc.) ) And the like. However, there is no particular limitation. Examples of the coating method for masking the electrode portion include vapor deposition, application, and application of an insulating tape. These are not particularly limited, but in order to cope with various film widths, it is preferable to apply an insulating tape with an arbitrary width to the electrodes.

  Next, the sagging of the film will be described. A film stretched by the tenter method has a difference in physical properties in the width direction due to the bowing phenomenon. In particular, when the relaxation of the shrinkage stress is insufficient, a difference in the amount of shrinkage appears depending on the position in the width direction. As a result, the length of the film in the width direction is different, and it is observed that the flatness of the film is deteriorated. When quantifying sagging, the surface layer of the film wound up in a roll is cut open in the width direction and developed. Then, since the film is released from the tension at the time of winding and the slack is restored, when the length in the flow direction, that is, the circumferential direction is measured at an arbitrary position in the width direction, the length varies depending on the measurement position. At this time, the amount of sag is defined as follows from the maximum and minimum values of the measured length.

Sag amount = (maximum value−minimum value) ÷ maximum value × 1000
The amount of sag can be controlled by the cooling rate of the heat-set film. That is, by reducing the cooling rate of the film, the amount of sag in which the relaxation of the contraction stress proceeds is reduced. On the other hand, when the film cooling rate is high, the amount of sag is increased due to insufficient relaxation of the shrinkage stress.

  Further, when the position where the length in the flow direction takes the maximum value is within 80% from the center in the width direction of the film, the shape is said to be slack. Otherwise, it is expressed as hanging.

In the present invention, the polyamide film preferably has a slender shape. When it is not slack, it is easy to block the vicinity of the central portion along the width direction of the film, and it is difficult to obtain the effect of the non-corona treatment at both ends.

  The amount of sag is preferably 0.5 to 2.0. If the amount of sag is less than 0.5, the flatness of the film is excellent, but the effect of non-treatment at both ends is reduced, and blocking becomes easy. If the amount of sag exceeds 2.0, wrinkles will occur in the original fabric, and various problems will occur in secondary processing even in the product roll after slitting.

In the present invention, the corona treatment is preferably adjusted so that the wetting tension of the polyamide film is 44 to 52 mN / m. More preferably, it is 46-50 mN / m. The wet tension in the above range can be achieved by appropriately adjusting the degree of corona treatment. When the wetting tension exceeds 52 mN / m, blocking tends to occur and the film deteriorates. When it is less than 44 mN / m, the adhesiveness after the secondary processing is inferior, and problems such as occurrence of peeling on the laminated film during boil / retort are likely to occur.

In the present invention, the polyamide film, Ru film der composed mainly of a polyamide resin. As the polyamide resin, a polyamide resin obtained by polycondensation of a lactam having three or more members, a polymerizable ω-amino acid, a dibasic acid and a diamine can be used. Specifically, polymers such as ε-caprolactam, aminocaproic acid, enanthractam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone; hexamethylenediamine, nona Polycondensation of diamines such as methylenediamine, undecamethylenediamine, dodecamethylenediamine, and metaxylylenediamine with dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, dodecanedioic acid, and glutaric acid Examples thereof include polymers obtained by caulking, and copolymers thereof. For example, nylon 4, 6, 7, 8, 11, 12, 6 · 6, 6 · 10, 6 · 11, 6 · 12, 6T, 6/6 · 6, 6/12, 6 / 6T, 6I / 6T Etc. From the viewpoint of excellent mechanical properties and thermal properties, the polyamide film for packaging is preferably composed mainly of nylon 6.

  Furthermore, various additives and modifiers that are usually blended as necessary, for example, lubricants, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, tackifiers, Sealing property improvers, antifogging agents, crystal nucleating agents, mold release agents, plasticizers, crosslinking agents, flame retardants, colorants (pigments, dyes, etc.) and the like may be blended.

  In addition, for the purpose of imparting functionality, an inline coating stretching technique may be used to coat an unstretched polyamide film with an antistatic agent, an adhesion improving composition, a barrier resin, etc., and then stretching the film. it can.

  The polyamide film may be a single layer film or a coextruded laminated film if the surface layer is polyamide.

Hereinafter, the present invention will be specifically described by way of examples. However, this invention is not limited to these unless it deviates from the summary.
In addition, each physical property of the film was calculated | required by the method shown below.

  (1) Wetting tension: Measured according to JIS K6768.

  (2) Slack amount: The surface layer of the roll roll wound up to a diameter of 600 mm or more is cut open in the width direction and released from the tension at the time of winding to restore the slack, and then at a pitch of 50 mm in the width direction. The length in the circumferential direction was measured. From the maximum value and the minimum value, the amount of sag was obtained by the following equation.

      Sag amount = (maximum value−minimum value) ÷ maximum value × 1000

(3) Blocking When the film was unwound from the original roll and slit, the film was peeled off from the original roll and judged according to the following criteria.

○: There was no peeling sound and it was possible to unwind easily.
(Triangle | delta): Although peeling sound was recognized, it was able to unwind without tearing a film.
X: The film was torn and could not be unwound from the roll.

(4) Laminate strength (Examples 1 to 9, Comparative Example 2): 4 polyurethane adhesives for dry lamination (A515 / A50, manufactured by Takeda Pharmaceutical Company Limited) were applied to one side of the polyamide film slit to a width of 800 mm. ˜5 g / m ^{2 was} applied and a polyester film (Unitika, PET-12, 12 μm) was laminated by a dry laminating method (temperature 80 ° C., pressure 490 kPa). Next, unstretched polypropylene for dry lamination (manufactured by Tosero Co., Ltd., RXC-18, 60 μm) was laminated on the other surface in the same manner to obtain a laminate having a polyester / polyamide / polypropylene film configuration.

  A film laminate cut to a width of 15 mm was used as a sample, and peeled at a tensile rate of 300 mm / min by a T-type peeling method in an environment of 20 ° C. × 65% RH, and the laminate strength was measured. At this time, the laminate strength of the polyester / polyamide and the laminate strength of the polyamide / polypropylene were measured. A polyester / polyamide having a value of 2 N / cm and higher and a polyamide / polypropylene having a value of 4 N / cm and higher are extremely suitable as packaging films.

Example 1
Using an extruder and a T-die, Unitika Nylon 6 (grade A1030BRF) was melted at a temperature of 235 ° C. and extruded as an unstretched sheet. The surface temperature was adjusted to 15 ° C. and closely adhered, and cooled. An unstretched sheet having a thickness of 150 μm was obtained.

The obtained sheet was sent to a hot water tank whose temperature was adjusted to 70 ° C. and subjected to a humidity conditioning treatment for 1 minute. Thereafter, both ends of the sheet in the width direction are held by a clip of a flat simultaneous biaxial stretching machine and subjected to simultaneous biaxial stretching at a stretching ratio of 3.0 times in length and 3.3 times in width at 195 ° C. did. Thereafter, heat treatment was performed at 200 ° C. for 3 seconds with a lateral relaxation rate of 5%. And the film was cooled at 150 degreeC for 2 second, and it took up with the take-off machine, and the grip margin of the clip in the both ends of the width direction of a film was cut. The width of the polyamide film obtained by cutting was 3500 mm. Next, the corona discharge electrodes are masked with insulating tape at locations opposite to both ends in the film width direction, and the first surface on the front side of the polyamide film is subjected to corona treatment, leaving 30 mm in both ends in the width direction, respectively. The second surface on the back side was also subjected to corona treatment. The conditions for the corona treatment were an air atmosphere, the distance between the film and the electrode was 1 mm, and the treatment power was 20 W · min / m ² . Subsequently, the film was wound with a winder to obtain a polyamide film having a thickness of 15 μm. Table 1 shows the results of measuring the amount of sagging based on the cooling rate of the heat-set film, the wetting tension based on the degree of corona treatment, the blocking performance, and the laminate strength of the obtained film.

Examples 2-9, Comparative Examples 1-3
As shown in Table 1, the film width, the width of the non-corona treated portion, and the amount of sagging were changed. In Example 5, cooling was performed at 180 ° C. for 2 seconds, and in Example 6, cooling was performed at 100 ° C. for 2 seconds. In Example 7, the center of the film was cooled at 180 ° C. and the end of the film was cooled at 150 ° C. for 2 seconds. In Example 8, the corona treatment power of the second surface was 30 W · min / m ^2, and in Example 9, the corona treatment power of the first surface was 15 W · min / m ² . Other than that was carried out similarly to Example 1, and obtained the film. Table 1 shows the results of measuring the amount of sag, wetting tension, blocking performance, and laminate strength of the obtained polyamide film.

Examples 1 to 5 and Example 8 were polyamide films without causing blocking and having high laminate strength. However, in Example 4, since the non-corona treatment part was widened, the ratio of the double-sided corona part to be a product was low and the cost was slightly high.

  The film of Example 6 was also a polyamide film having high lamination strength without causing blocking. However, due to the large amount of sagging, the original fabric had some wrinkles.

  In the case of Example 7, the slack shape was suspended, but the corona-treated non-treated portion was formed at the end that is easily affected by the external environment, so that no breakage due to blocking occurred during film winding. It was.

In Example 9, since the degree of corona treatment was low, blocking was not caused, but the laminate strength was slightly low.
Since the thing of the comparative example 1 did not make the non-processing part in the edge part of the width direction of a film, blocking generate | occur | produced with the original fabric. For this reason, it could not be used for lamination.

The thing of the comparative example 2 was expensive as an industrial production machine stand, since the width | variety of the original fabric was too narrow.
In Comparative Example 3, since the width of the original fabric to be obtained was too wide, breakage occurred in the stretching process. For this reason, the stretched polyamide film was not obtained.

Claims (6)

A polyamide film having a width of 2000 mm to 5000 mm, corona treatment on both surfaces, and non-corona treatment portions formed on both ends in the width direction on at least one surface. 2. The polyamide film according to claim 1, wherein the amount of sag is 0.5 to 2.0. The polyamide film according to claim 1 or 2, wherein the wet tension is 44 to 52 mN / m on both sides. Polyamide film having both surfaces a method for producing a polyamide film which has been corona treated on both end portions in the width direction of at least one surface of the polyamide film width 2000Mm～5000mm, and forming respectively the untreated portion of the corona treatment Manufacturing method. The method for producing a polyamide film according to claim 4, wherein the amount of sag of the polyamide film is 0.5 to 2.0. Method for producing a polyamide film according to claim 4 or 5, wherein the to 44~52mN / m both surfaces the wetting tension of the polyamide film.