JP2008045015A - Biaxially oriented nylon film, laminated packaging material and method for producing biaxially oriented nylon film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented nylon film which is excellent in formability, strength and pin hole resistance as a main substrate for cold forming packaging materials and the like, to provide a laminated packaging material containing the same, and to provide a method for producing the biaxially oriented nylon film. <P>SOLUTION: This biaxially oriented nylon film comprises a virgin raw material comprising Ny6 and MXD6 and a heat history product produced by melt-kneading Ny6 with MXD6 and having a MXD6 melting point of 233 to 238°C as raw materials and is characterized in that the hot water shrinkage rate of the film is 3 to 20%; the breaking elongations of the film in four directions (MD direction, TD direction, 45°direction, 135°) in a tensile test is ≥70%; and a stress ratio A (σ<SB>1</SB>/σ<SB>2</SB>) of a tensile stressσ<SB>1</SB>at an elongation of 50% to a tensile stressσ<SB>2</SB>at yield point in a stress-strain curve in the tensile test of the film is ≥2 in each of the above-mentioned four directions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a biaxially stretched nylon film, a laminate packaging material, and a method for producing a biaxially stretched nylon film.

  Biaxially stretched nylon films (hereinafter also referred to as ONy films) are excellent in strength, impact resistance, pinhole resistance, etc., and are therefore often used in applications where heavy strength loads such as heavy weight packaging and water packaging are applied. .

Here, conventionally, a technique of using nylon as a packaging material for molding such as deep drawing molding or stretch molding is known (see, for example, Patent Documents 1 and 2).
Specifically, Patent Document 1 discloses a material for cold forming having a base material layer containing a polystyrene-based resin and one or more functional layers laminated on one or both surfaces of the base material layer. A resin sheet is shown. And the structure which provides the abrasion-resistant layer containing a nylon resin in the surface layer of the resin sheet for cold forming as the said functional layer is shown.
According to such a cold-molding resin sheet, it is possible to obtain a cold-molded product having excellent impact resistance and shape retention. And by providing a wear-resistant layer containing a nylon resin on the surface layer, it is possible to prevent the surface layer of the sheet from being damaged during cold forming.
In addition, as described in Patent Document 1, cold forming is superior to hot forming in that a heating device is not required, the size of the device can be reduced, and high-speed continuous forming is possible. ing.

On the other hand, in Patent Document 2, a seal layer is a polypropylene resin layer, an intermediate layer is an oxygen barrier resin layer, a nylon resin layer, and a polyethylene resin layer, and the outermost layer is formed by laminating a sheet made of a hygroscopic material. A drawing sheet composite sheet is shown.
According to such a deep drawing composite sheet, a mechanical strength can be imparted to the composite sheet by providing the intermediate layer with a nylon resin layer. This makes it possible to prevent the occurrence of pinholes during deep drawing at about 150 ° C.

JP 2004-74795 A JP 2004-98600 A

  However, in Patent Document 1, since there is no specific description about the nylon resin layer provided on the surface layer of the cold-molding resin sheet, depending on the nylon resin layer used, good moldability and strength in cold molding, It may not show pinhole resistance. In this case, a molded product having a sharp shape cannot be obtained, and pinholes may occur in the sheet during cold forming.

  Further, in Patent Document 2, although there is a specific description of the raw material used for the nylon resin layer, there is no specific description of mechanical properties such as elongation of the nylon resin layer. Furthermore, although deep drawing at about 150 ° C. is mentioned, it is not mentioned about cold forming. For this reason, like the above-mentioned patent document 1, there is a possibility that a good molded product cannot be obtained by cold forming.

  Accordingly, an object of the present invention is to provide a biaxially stretched nylon film excellent in formability, strength and pinhole resistance, a laminate packaging material including the biaxially stretched nylon film as a main base material such as a cold molding packaging material, and the biaxial It is providing the manufacturing method of a stretched nylon film.

The gist of the present invention is as follows.
(1) A virgin raw material composed of nylon 6 (hereinafter also referred to as Ny6) and metaxylylene adipamide (hereinafter also referred to as MXD6), Ny6 and MXD6 were melt-kneaded to set the melting point of MXD6 to 233 to 238 ° C. A biaxially stretched nylon film containing a heat history product as a raw material, and when the film is held in hot water at 95 ° C. for 30 minutes, the hot water shrinkage in the MD and TD directions of the film is 3 to 3 20%, elongation to break in 4 directions (MD direction, TD direction, 45 ° direction, 135 ° direction) in the tensile test of the film (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) rate is 70% or more, and stress in the tensile test of the film - in strain curve, the tensile stress when the elongation became 50% sigma When biaxially oriented nylon film, which is a ratio of the tensile stress sigma ₂ at the yield point stress ratio A (σ _{1 /} σ ₂₎ is at both 2 above for the four directions.
(2) In the biaxially stretched nylon film described in the above (1), among the stress ratios A in the four directions, the ratio of the maximum stress ratio _Amax and the minimum stress ratio _Amin (A _max / _Amin ) is 2 or less, The biaxially-stretched nylon film characterized by the above-mentioned.
(3) The biaxially stretched nylon film according to (1) or (2) above, wherein the tensile rupture strength in the four directions in the tensile test of the film is 180 MPa or more. Stretched nylon film.
(4) In the biaxially stretched nylon film according to any one of (1) to (3), the virgin raw material is composed of 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6, and the heat A biaxially stretched nylon film characterized in that the content of a history product is 5 to 40% by mass based on the total amount of the raw materials.
(5) In the biaxially stretched nylon film described in (1) to (4) above, the blending ratio of Ny6 and MXD6 in the heat history product is Ny6: MXD6 = 60 to 85 parts by mass: 15 to 40 parts by mass. A biaxially stretched nylon film characterized by being.
(6) A laminate packaging material comprising the biaxially stretched nylon film according to any one of (1) to (5).
(7) A method for producing a biaxially stretched nylon film comprising, as raw materials, a virgin raw material composed of Ny6 and MXD6 and a heat history product in which Ny6 and MXD6 are melt-kneaded to have a melting point of MXD6 of 233 to 238 ° C. Biaxially stretched under the condition that the stretching ratio in the MD direction (film movement direction) and TD direction (film width direction) is 2.8 times or more with respect to the unstretched raw film composed of the raw materials. Then, heat treatment is performed at 160 to 200 ° C., and when the film is held in hot water at 95 ° C. for 30 minutes, the hot water shrinkage in the MD direction and TD direction of the film is 3 to 20%, Four directions (MD direction, TD direction, 45 ° direction, 135 °) in the tensile test of the film (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) Elongation to failure of direction) is 70% or more, and stress in the tensile test of the film - in strain curve, the tensile stress sigma ₁ when the elongation rate was 50%, a tensile at yield point stress sigma ₂ ratio a is stress ratio a (σ _{1 /} σ ₂₎ with the production of biaxially oriented nylon film and forming a biaxially oriented nylon film is either 2 or more for the four directions Method.

  According to the ONy film of the present invention, the elongation ratio until breaking in four directions in the tensile test of the ONy film is 70% or more, and the stress ratio A in the stress-strain curve of the ONy film is in each direction. Since it is 2 or more, it has excellent moldability, strength and pinhole resistance, and can exhibit these characteristics particularly during cold forming. Moreover, since the hot water shrinkage rate of the ONy film when held in hot water at 95 ° C. for 30 minutes is 3 to 20%, it exhibits good elongation characteristics during molding. And, according to the laminate wrapping material configured to include such an ONy film, a sharp shaped molded product can be obtained without generating a pinhole in the ONy film during cold drawing or the like. Can be manufactured. Moreover, since MXD6 is contained in the ONy film, the packaging material exhibits excellent heat resistance. For this reason, when the packaging material is formed by laminating an ONy film layer and a sealant layer, and the packaging material is heated and sealed with a seal bar, the packaging material does not adhere to the seal bar, and a good seal is obtained. Processing can be realized. Furthermore, according to the packaging material, since the heat history product is contained in the ONy film, it is possible to prevent delamination within the ONy film and obtain a molded product having excellent impact resistance.

  In the present invention, cold forming refers to forming performed in a temperature atmosphere less than the glass transition point (Tg) of the resin. Such cold forming is preferably performed by using a cold forming machine used for forming aluminum foil or the like and pressing the sheet material with a male die against a female die and pressing at a high speed. Plastic deformation such as molding, bending, shearing and drawing can be generated without heating.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
[Configuration of biaxially stretched nylon film]
The biaxially stretched nylon film (ONy film) according to the present embodiment is a biaxial unstretched raw film containing a virgin raw material composed of Ny6 and MXD6 and a heat history product formed by melting and kneading Ny6 and MXD6 as raw materials. It is formed by stretching and heat treatment at a predetermined temperature. Thus, an ONy film excellent in impact resistance can be obtained by biaxially stretching an unstretched raw film.
Here, the chemical formula of Ny6 is shown in the following chemical formula 1, and the chemical formula of MXD6 is shown in the chemical formula 2 below.

The above-mentioned virgin raw material usually means a raw material that is not a mixed raw material having a history in which Ny6 and MXD6 are mixed and melt-kneaded. For example, even if Ny6 and MXD6 have a history of being melt-kneaded independently (for example, recycled products), they are virgin raw materials when they are not mixed and melt-kneaded.
The blending ratio of Ny6 and MXD6 in the virgin raw material is preferably 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6 from the viewpoint of impact strength and heat resistance of the ONy film. In addition, when MXD6 in the virgin raw material is less than 15 parts by mass, the heat-resistant effect is reduced, and the ONy film is laminated with an appropriate sealant film to form a laminate packaging material. May adhere to the seal bar. Moreover, when there is more MXD6 than 40 mass parts, impact strength will fall significantly and it will become scarce practicality.

The above-mentioned heat history product is a blended product of Ny6 and MXD6, which has passed through the extruder once. For the present invention, the melting point of MXD6 is 233 to 238 ° C., preferably with a scanning scanning calorimeter (DSC). Use what was hold | maintained in the range of 235-237 degreeC. The heat history product may be a recycled ONy film obtained according to the present embodiment. Since such a heat history product functions as a compatibilizing agent having affinity for both Ny6 and MXD6, the occurrence of in-layer peeling can be prevented by adding such a heat history product to the ONy film.
Here, delamination refers to a phenomenon that causes delamination within the ONy film when it is used under severe conditions such as cold forming after laminating the ONy film with an appropriate sealant film. The mechanism of this delamination is not necessarily clear, but it is considered that Ny6 and MXD6 are oriented in layers in the ONy film, and delamination occurs at the interface.
Moreover, the melting point of MXD6 in the heat history product refers to a melting point measured in a state before being melt kneaded with the virgin raw material. When the melting point of MXD6 in the heat history product is less than 233 ° C., the impact strength of the ONy film is lowered. In addition, when the melting point of MXD6 in the heat history product is 238 ° C. or higher, the effect of preventing in-layer peeling is reduced.

The content of the heat history product is preferably 5 to 40% by mass based on the total amount of raw materials. When the heat history product is less than 5% by mass, the use of an ONy film as a laminate film under severe conditions such as cold forming tends to cause delamination within the layer. Moreover, when a heat history product exceeds 40 mass%, the impact strength of an ONy film will fall.
The blending ratio of Ny6 and MXD6 in the heat history product is preferably Ny6: MXD6 = 60 to 85 parts by mass: 15 to 40 parts by mass from the viewpoint of impact strength and the effect of preventing in-layer peeling. In addition, when the blending ratio of MXD6 in the heat history product is less than 15 parts by mass (the blending ratio of Ny6 is more than 85 parts by mass), the effect of preventing the on-layer peeling of the ONy film is lowered. When the mixing ratio of MXD6 in the heat history product exceeds 40 parts by mass (the mixing ratio of Ny6 is less than 60 parts by mass), the impact strength of the ONy film decreases.

  The ONy film according to the present embodiment has a hot water shrinkage of 3 to 20%, preferably 6 in the MD direction and the TD direction when the film is held in hot water at 95 ° C. for 30 minutes. Must be ~ 20%. By doing in this way, the ONy film excellent in the elongation characteristic at the time of shaping | molding compared with a normal ONy film can be obtained, for example, the fracture | rupture of an ONy film at the time of cold forming and generation | occurrence | production of a pinhole can be prevented. When the hot water shrinkage rate of the film is less than 3%, there is no great difference in elongation characteristics at the time of molding as compared with a normal ONy film. On the other hand, when the hot water shrinkage rate of the film exceeds 20%, a laminate phenomenon is formed between the ONy film and another film layer when the ONy film and another film layer are laminated to form a laminate packaging material. (Delami) may occur.

In this embodiment, the elongation rate until the tensile rupture in four directions (MD direction, TD direction, 45 ° direction, 135 ° direction), the stress ratio A, and the tensile rupture stress of the ONy film are the tensile test ( The sample width is 15 mm, the distance between the gauge points is 50 mm, and the tensile speed is 100 mm / min), and is obtained based on the stress-strain curve obtained thereby.
Here, examples of the stress-strain curve obtained by the tensile test include those shown in FIG.
In FIG. 1, the vertical axis represents the tensile stress σ (MPa) of the ONy film, and the horizontal axis represents the strain ε (ε = Δl / l, l: initial length of the film, Δl: increased length of the film) of the ONy film. Show. When the tensile test of the ONy film is performed, the tensile stress σ increases in a substantially linear function as the strain ε increases, and the increasing tendency of the tensile stress σ greatly changes at a predetermined strain ε ₁ . In the present invention, this point (ε ₁ , σ ₂ ) is defined as the yield point. When the strain ε further increases, the tensile stress σ also increases with this, and when the strain ε ₂ is reached, the film breaks. Such stress-strain curves are acquired in four directions (MD direction, TD direction, 45 ° direction, and 135 ° direction) for each ONy film.

In the ONy film according to the present embodiment, the elongation rate until breakage in four directions (MD direction, TD direction, 45 ° direction, 135 ° direction) in the tensile test needs to be 70% or more. That is, as in the stress-strain curve of FIG. 1, the strain ε ₂ at the time of film breakage needs to be 0.7 or more. As a result, the ONy film can be stretched in a well-balanced manner, and the drawability when the laminate material is obtained is improved. In addition, when the elongation percentage of any one of the four directions is less than 70%, the film is likely to be broken at the time of cold deep drawing or the like, and good moldability cannot be obtained.
At this time, it is more preferable that the value obtained by dividing the maximum elongation by the minimum elongation among the elongations in these four directions is 2.0 or less. As a result, the ONy film is stretched with a better balance.
Further, if the elongation rate in the four directions of the ONy film is 75% or more and the value obtained by dividing the maximum elongation rate by the minimum elongation rate among the elongation rates in these four directions is 2.0 or less, it is even better. It is desirable because moldability is obtained.

In the ONy film according to this embodiment, for example, in the stress-strain curve shown in FIG. 1, the tensile stress σ ₁ when the elongation is 50% (strain ε = 0.5) and the tensile stress σ at the yield point. _The stress ratio A (σ ₁ / σ ₂ ), which is a ratio to 2, needs to be 2 or more, more preferably 2.2 or more in any of the four directions. As a result, pinholes can be reliably prevented from occurring during cold deep drawing or the like, and a sharp shaped molded product can be manufactured. In addition, if the stress ratio A in any one direction is less than 2, uneven thickness is poor and locally thins, and the film may break.
At this time, the ratio (A _max / A _min ) between the maximum stress ratio A _max and the minimum stress ratio A _min among the respective stress ratios A in these four directions is preferably 2.0 or less, more preferably 1 .8 or less is desirable. Thereby, a film is extended with sufficient balance at the time of cold forming, and a molded product having a uniform thickness can be manufactured. In addition, when _Amax / _Amin exceeds 2.0, uneven thickness will be bad and it will become thin locally and a film may fracture | rupture.

Furthermore, the ONy film according to the present embodiment preferably has a tensile breaking strength (σ ₃ ) in four directions of 180 MPa or more, for example, in the stress-strain curve shown in FIG. Thereby, sufficient processing strength can be obtained, and the ONy film is more difficult to break during cold drawing or the like. At this time, if the value obtained by dividing the maximum strength by the minimum strength among the tensile rupture strengths in the four directions is 2.0 or less, it is preferable because a processing strength excellent in balance can be obtained.
Further, if the tensile breaking strength in four directions of the ONy film is 200 MPa or more and the value obtained by dividing the maximum strength by the minimum strength among the tensile breaking strengths in the four directions is 1.8 or less, the balance is more excellent. It is preferable because a high processing strength can be obtained.

[ONy film manufacturing method]
The ONy film as described above is in the MD direction and the TD direction with respect to the unstretched raw film made of the raw material containing the virgin raw material made of Ny6 and MXD6 and the heat history product at a predetermined mixing ratio. It can be obtained by biaxial stretching under conditions where the stretching ratio is 2.8 times or more and then heat-treating at 160 to 200 ° C.
As the biaxial stretching method, for example, simultaneous biaxial stretching by the tubular method or tenter method or sequential biaxial stretching can be adopted, but it is preferable to carry out by simultaneous biaxial stretching by the tubular method from the viewpoint of the longitudinal and lateral strength balance. .
Ny6 and MXD6 constituting the virgin raw material are preferably used by dry blending pellets. Moreover, it is preferable to use a pellet in the heat history product. For example, the biaxially stretched nylon film obtained by this embodiment may be finely cut and compressed into pellets. Thus, the heat history product can be suitably dry blended with the Ny6 pellets and the MXD6 pellets.

Specifically, the ONy film of this embodiment can be manufactured as follows.
First, after Ny6 pellets, MXD6 pellets and pellet-like heat history products are melt-kneaded at 270 ° C. in an extruder, the melt is extruded from a die as a cylindrical film, and then rapidly cooled with water to produce a raw film. .
Next, for example, as shown in FIG. 2, the raw film 11 is inserted between a pair of nip rolls 12 and then heated by a heater 13 while a gas is being pressed into the film 11. 15 was blown to expand into bubbles 16 and taken up by a pair of downstream nip rolls 17 to perform simultaneous biaxial stretching in the MD direction and the TD direction by the tubular method. At this time, the respective draw ratios in the MD direction and the TD direction need to be 2.8 times or more. When the draw ratio is less than 2.8 times, the impact strength is lowered, causing a problem in practicality.
Thereafter, this stretched film is put in a tenter type heat treatment furnace (not shown) and heat-set at 160 to 200 ° C., whereby the ONy film 18 of the present embodiment can be obtained.

[Composition of laminate packaging material]
The laminate packaging material of the present embodiment is configured by laminating one or two or more other laminate base materials on at least one surface of the above-described ONy film. Specifically, examples of other laminate base materials include an aluminum layer, a film including an aluminum layer, and a sealant layer.
In general, a laminate packaging material including an aluminum layer is not suitable for cold forming because the aluminum layer easily breaks due to necking during cold forming. In this regard, according to the laminate packaging material of the present embodiment, the above-described ONy film has excellent moldability, impact resistance, and pinhole resistance. Moreover, the breakage of the aluminum layer can be suppressed, and the occurrence of pinholes in the packaging material can be suppressed. Therefore, even when the total packaging material thickness is thin, a molded product having a sharp shape and high strength can be obtained.
Moreover, since MXD6 is contained in the ONy film layer, the packaging material exhibits excellent heat resistance. For this reason, when the said packaging material is provided with the sealant layer, when the said packaging material is heated and sealed with a seal bar, the said packaging material does not adhere to a seal bar, but a favorable sealing process is realizable.
Furthermore, according to the packaging material, since the heat history product is included in the ONy film layer, molding with excellent impact resistance without causing a peeling phenomenon in the ONy film layer during cold molding or the like. Goods can be obtained.

  The laminate packaging material of this embodiment preferably has an overall thickness of the ONy film and other laminate base material of 200 μm or less. When the total thickness exceeds 200 μm, it becomes difficult to form the corner portion by cold forming, and there is a possibility that a molded product having a sharp shape cannot be obtained.

  The thickness of the ONy film in the laminate packaging material of this embodiment is desirably 5 to 50 μm, more preferably 10 μm to 30 μm. Here, when the thickness of the ONy film is smaller than 5 μm, the impact resistance of the laminate packaging material becomes low, and the cold formability becomes insufficient. On the other hand, when the thickness of the ONy film exceeds 50 μm, the effect of further improving the impact resistance of the laminate packaging material cannot be obtained, and the total thickness of the packaging material only increases, which is not preferable.

As an aluminum layer used for the laminate packaging material of this embodiment, an aluminum foil made of a soft material of pure aluminum or an aluminum-iron alloy can be used. In this case, from the viewpoint of improving the laminating performance, the aluminum foil is subjected to a pretreatment such as an undercoat treatment or a corona discharge treatment with a silane coupling agent or a titanium coupling agent, and then laminated on the ONy film. Is preferred.
The thickness of such an aluminum layer is preferably 20 to 100 μm. Thereby, it becomes possible to hold | maintain the shape of a molded article favorably, and it can prevent that oxygen, a water | moisture content, etc. permeate | transmit the inside of a packaging material.
When the thickness of the aluminum layer is less than 20 μm, the aluminum layer is likely to break during cold forming of the laminate packaging material, and pinholes and the like are likely to occur even if the aluminum layer is not broken. For this reason, there exists a possibility that oxygen, a water | moisture content, etc. may permeate | transmit the inside of a packaging material. On the other hand, when the thickness of the aluminum layer exceeds 100 μm, neither the improvement effect of breaking during cold forming nor the effect of preventing pinhole generation is particularly improved, and it is preferable because the total thickness of the packaging material is merely increased. Absent.

Although the best configuration for carrying out the present invention has been disclosed in the above description, the present invention is not limited to this. That is, the present invention has been described primarily with reference to specific embodiments, but with respect to the above-described embodiments without departing from the scope of the technical idea and object of the present invention, the material, quantity, and other details. In this configuration, those skilled in the art can make various modifications.
Accordingly, the description of the materials, layer structures, and the like disclosed above is exemplary for easy understanding of the present invention, and does not limit the present invention. Descriptions with names excluding some or all of the limitations are included in the present invention.

For example, in this embodiment, the tubular method is adopted as the biaxial stretching method, but a tenter method may be used. Furthermore, the stretching method may be simultaneous biaxial stretching or sequential biaxial stretching.
In addition, necessary additives can be appropriately added to the ONy film. Examples of such additives include anti-blocking agents (such as inorganic fillers), water repellents (such as ethylene bis stearates), and lubricants (such as calcium stearate).
Furthermore, in the said embodiment, although the laminate packaging material which laminated | stacked the aluminum layer, the sealant layer, etc. on the ONy film was illustrated, it is not limited to this, As a laminate packaging material of this invention, an antistatic layer, a printing layer, There may be mentioned a laminate in which various functional layers such as a barrier layer and a strength reinforcing layer are laminated.

Next, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples.
[Examples 1 and 2]
(Manufacture of stretched film)
Ny6 pellets and MXD6 pellets are mixed at a ratio of 70 parts by weight and 30 parts by weight, respectively, and heat history products that have already been melt-mixed and pelletized at this blending ratio (with a melting point of MXD6 of 236 ° C) ) Was blended in an amount of 10% by mass based on the total amount of raw materials. After this dry blend product was melt-kneaded at 270 ° C. in an extruder, the melt was extruded as a cylindrical film from a die and then rapidly cooled with water to produce a raw film.
The melting point of MXD6 was measured by increasing the temperature from 50 ° C. to 280 ° C. at a temperature increase rate of 10 ° C./min using a differential scanning calorimeter (DSC) manufactured by PerkinElmer. In all cases, the value in the first run was taken as the melting point.
What was used as Ny6 is nylon 6 [UBE nylon 1023FD (trade name), relative viscosity ηr = 3.6] manufactured by Ube Industries, Ltd., and what was used as MXD6 is a product manufactured by Mitsubishi Gas Chemical Co., Ltd. Xylylene adipamide [MX nylon 6007 (trade name), relative viscosity ηr = 2.7].
Moreover, the mixture ratio of Ny6 and MXD6 was 70 parts by mass and 30 parts by mass, respectively, and 40φEX, a single screw (manufactured by Yamaguchi Seisakusho Co., Ltd.) was used and extruded at 270 ° C. to obtain a heat history product.
Next, as shown in FIG. 2, the raw film 11 is inserted between a pair of nip rolls 12 and then heated with a heater 13 while a gas is being pressed into the film 11. Was blown into the bubble 16 and taken up by a pair of downstream nip rolls 17 to perform simultaneous biaxial stretching in the MD direction and the TD direction by the tubular method. The magnification during this stretching was 3.0 times in the MD direction and 3.2 times in the TD direction.
Next, this stretched film was put into a tenter type heat treatment furnace (not shown), and heat-set at 200 ° C., and had a hot water shrinkage ratio of 15 μm, 3.4% according to Example 1. The obtained ONy film 18 was obtained.
In the ONy film 18 according to Example 2, the blending ratio of the heat history product is 20% by mass with respect to the total amount of raw materials in the manufacturing operation of Example 1 described above, and the stretched film is heated at 160 ° C. in a tenter type heat treatment furnace. Manufactured under the same conditions except for the fixed points. In Example 2, the hot water shrinkage percentage was 19%, and the film thickness was 15 μm.

[Evaluation methods]
(Tensile test)
The tensile test of the ONy film 18 was carried out using an Instron type 5564 type, with a sample width of 15 mm, a chuck interval of 50 mm, and a tensile speed of 100 mm / min. Measurement was performed for each of the MD direction / TD direction / 45 ° direction / 135 ° direction of the ONy film 18. Based on the stress-strain curve obtained in each direction, the elongation at break (%) in each direction, the ratio between the maximum value and the minimum value of these elongation at break, and the stress ratio A in each direction (A = σ ₁ / σ ₂ , σ ₁ : tensile stress at an elongation of 50%, σ ₂ : tensile stress at the yield point), and the maximum value A _max and the minimum value A _{min of} these stress ratios A The ratio was calculated.

(Drawing formability)
The drawability of the laminate packaging material including the ONy film 18 was evaluated.
Specifically, first, the ONy film 18 according to Examples 1 and 2 was used as a front substrate film, and an L-LDPE film [Unilux LS-711C (trade name), manufactured by Idemitsu Unitech Co., Ltd., thickness 120 μm] Was used as a sealant film to dry laminate them to obtain a laminate packaging material. In addition, as an adhesive for dry lamination, a blended product of Takelac A-615 / Takenate A-65 (mixing ratio 16/1) manufactured by Mitsui Takeda Chemical was used. The laminated packaging material after dry lamination was aged at 40 ° C. for 3 days.
Each laminate packaging material thus produced was deep-drawn with cold (normal temperature) using a rectangular (5 mm × 10 mm) mold in plan view. This deep drawing was performed 10 times for each laminate packaging material, and the number of defects such as pinholes and cracks was examined. When the number of occurrences of defects was 0 out of 10 times, the evaluation was evaluated as 、, when it was 1 to 2 times, ◯, when it was 3 to 5 times, and when it was 6 times or more, ×.

(In-layer peelability)
A laminate packaging material was prepared in the same manner as in the drawability evaluation described above, a strip-shaped test piece having a width of 15 mm was cut out from the laminate packaging material, and the end portion of the laminate was peeled off by several centimeters by hand, and the front substrate film Separated into (ONy film 18) and sealant film. Thereafter, each film piece was set in a tensile tester (Instron universal tester 1123 type), and a peel test of the laminate portion was performed at a speed of 300 mm / min (90 ° peel).
In the middle of the peel test, if peeling inside the surface substrate film occurs, the peel strength sharply decreases. Therefore, it can be determined whether or not such peeling has occurred, depending on whether or not such behavior has occurred. For example, at the start of the peel test, if the peel strength is about 7 N / m, but is suddenly reduced to about 1 to 2 N / m during the peel test, it can be determined that in-layer peel has occurred.
And the thing which did not show the behavior of peeling in a layer inside a surface base film was evaluated as ◯, and the thing which showed the behavior of peeling in a layer was evaluated as x.

(Seal resistance)
A laminate packaging material was produced in the same manner as the above-described drawability evaluation, and a sealing treatment was performed on the laminate packaging material. In the sealing process, the temperature of the seal bar was set to 200 ° C., the seal width was 5 mm (no Teflon (registered trademark) tape was applied), the seal time was 10 seconds, and the pressure of the seal bar was 2 kg / cm ² . . The seal resistance of the laminate packaging material is: ○ when the packaging material does not adhere to the seal bar when the sealing treatment is applied under the above conditions, Δ when the packaging material adheres to the seal bar, and the packaging material is sealed. Those that had a white appearance on the bar were evaluated as x.

[Comparative Example 1]
In the production operation of Example 1 above, the mixing ratio of the heat history product is 15% by mass with respect to the total amount of the raw material, and the comparison is performed in the same manner except that the stretched film is heat-set at 210 ° C. with a tenter type heat treatment furnace. An ONy film 18 according to Example 1 was produced. The hot water shrinkage of Comparative Example 1 was 2.8%, and the film thickness was 15 μm.

[Comparative Example 2]
The ONy film 18 according to Comparative Example 2 was manufactured in the same manner except that only Ny6 was used as a raw material and the stretched film was heat-set at 195 ° C. in a tenter-type heat treatment furnace among the manufacturing operations of Example 1 above. . In Comparative Example 2, the hot water shrinkage was 5%, and the film thickness was 15 μm.

These Comparative Examples 1 and 2 were also evaluated in the same manner as in Examples 1 and 2.
Table 1 shows constituent raw materials, heat history product content, heat treatment temperature, hot water shrinkage, and film thickness for Examples 1 and 2 and Comparative Examples 1 and 2, respectively. Table 2 shows the tensile test results for Examples 1 and 2 and Comparative Examples 1 and 2. Table 3 shows the evaluation results of drawability, in-layer peeling, and seal resistance for each of Examples 1 and 2 and Comparative Examples 1 and 2.

[Evaluation results]
As shown in Table 1, the ONy film 18 according to Examples 1 and 2 is excellent in all of drawability, delamination in layers and seal resistance as compared with Comparative Examples 1 and 2.
On the other hand, since the comparative examples do not satisfy the above-described conditions, there are problems in the physical properties of the ONy film 18. Specifically, Comparative Example 1 is inferior in drawability because the stress ratio A in the TD direction and 45 ° direction is less than 2. Moreover, since the comparative example 2 does not contain MXD6 in a raw material, it is inferior to seal resistance.

  The present invention can be used for cold forming packaging materials and the like.

An example of the stress-strain curve obtained when a tensile test is performed with respect to the ONy film which concerns on embodiment of this invention. Schematic of the biaxial stretching apparatus which manufactures the ONy film which concerns on the said embodiment.

Explanation of symbols

11 Raw film 16 Bubble 18 Stretched film

Claims (7)

Virgin raw material consisting of nylon 6 (hereinafter also referred to as Ny6) and metaxylylene adipamide (hereinafter also referred to as MXD6), Ny6 and MXD6 were melt-kneaded to obtain a heat history product having a melting point of MXD6 of 233-238 ° C. A biaxially stretched nylon film containing
When the film is held in hot water at 95 ° C. for 30 minutes, the hot water shrinkage in the MD direction and TD direction of the film is 3 to 20%,
Elongation rate to break in 4 directions (MD direction, TD direction, 45 ° direction, 135 ° direction) in the tensile test (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) of the film is 70% or more. And
Stress in the tensile test of the film - strain in the curve, the tensile stress sigma ₁ when the elongation rate was 50%, the ratio of the tensile stress sigma ₂ at the yield point stress ratio A (σ _{1 /} σ ₂ Is a biaxially stretched nylon film, wherein all of the four directions are 2 or more. In the biaxially stretched nylon film according to claim 1,
Of the respective stress ratios A in the four directions, the ratio (A _max / A _min ) between the maximum stress ratio A _max and the minimum stress ratio A _min is 2 or less. Axially stretched nylon film. In the biaxially stretched nylon film according to claim 1 or 2,
The biaxially stretched nylon film, wherein the tensile breaking strength in the four directions in the tensile test of the film is 180 MPa or more. In the biaxially stretched nylon film according to any one of claims 1 to 3,
The virgin raw material is composed of 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6.
Content of the said heat history goods is 5-40 mass% on the said raw material whole quantity basis. The biaxially-stretched nylon film characterized by the above-mentioned. In the biaxially stretched nylon film according to any one of claims 1 to 4,
The blend ratio of Ny6 and MXD6 in the heat history product is Ny6: MXD6 = 60 to 85 parts by mass: 15 to 40 parts by mass.   A laminate packaging material comprising the biaxially stretched nylon film according to any one of claims 1 to 5. A method for producing a biaxially stretched nylon film comprising, as raw materials, a virgin raw material comprising Ny6 and MXD6, and a heat history product in which the melting point of MXD6 is 233 to 238 ° C. by melting and kneading Ny6 and MXD6,
Biaxially stretched under the condition that the stretching ratio in the MD direction (film movement direction) and TD direction (film width direction) is 2.8 times or more with respect to the unstretched raw film composed of the raw materials. After that, heat treatment is performed at 160 to 200 ° C.
When the film is held in hot water at 95 ° C. for 30 minutes, the hot water shrinkage in the MD direction and TD direction of the film is 3 to 20%,
Elongation rate to break in 4 directions (MD direction, TD direction, 45 ° direction, 135 ° direction) in the tensile test (sample width 15 mm, distance between gauge points 50 mm, tensile speed 100 mm / min) of the film is 70% or more. And
Stress in the tensile test of the film - strain in the curve, the tensile stress sigma ₁ when the elongation rate was 50%, the ratio of the tensile stress sigma ₂ at the yield point stress ratio A (σ _{1 /} σ ₂ ) Form a biaxially stretched nylon film that is 2 or more in each of the four directions. A method for producing a biaxially stretched nylon film, wherein:

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