HK1155189B - Biaxially stretched polyamide resin film, and process for production thereof - Google Patents

Description

Biaxially oriented polyamide resin film and method for producing same

Technical Field

The present invention relates to a biaxially oriented polyamide resin film and a method for producing the same, and particularly to a biaxially oriented polyamide resin film which can be used for a polyamide resin package or container and a method for producing the same.

Background

Biaxially oriented polyamide resin films using nylon 6, nylon 66, or the like are excellent in mechanical properties such as tensile strength, puncture strength, pin hole strength, impact strength, and the like, and are excellent in gas barrier properties and heat resistance. Therefore, it is applied to a wide range of uses.

When these biaxially stretched polyamide resin films are used as packaging materials, they are generally used as a surface base material of a laminate film, and in many cases, they do not come into direct contact with the contents to be packaged. Therefore, the behavior of the low molecular weight compound in the biaxially oriented polyamide resin film has not been so far described.

However, when the film is heated in a film production process, a processing process such as lamination or printing, a compound having a small molecular weight contained in the polyamide resin film may be precipitated on the film surface. With the recent advancement of packaging technology, it has become impossible to disregard such a phenomenon and the resulting problems.

In order to cope with this problem, a polyamide resin having a large molecular weight of a monomer unit constituting the polyamide resin, for example, nylon 11, nylon 12, or a copolyamide resin having these as a main component has been proposed (JP4-325159 a). Alternatively, a polyamide resin obtained by copolymerizing 1, 6-hexamethylenediamine with sebacic acid has been proposed (JP 2001-328681A). However, these polyamides are special polyamides, and are expensive and have low versatility. Therefore, there is a strong demand for a membrane using nylon 6 or nylon 66 having high versatility and low monomer content.

In the case of polyamide resins, even when unreacted low-molecular-weight compounds such as monomers and oligomers are removed in the stage of chips before film molding, the low-molecular-weight compounds are regenerated when the resin chips are remelted by a melt extruder or the like. As a result, low molecular weight compounds remain in the film, and the quality thereof is degraded. In particular, polyamides mainly comprising caproamides as repeating units are relatively likely to produce low molecular weight compounds such as monomers, and have a characteristic of containing a large amount of low molecular weight compounds, as compared with polyamides comprising dicarboxylic acids and diamines.

In general, if the end group concentration of the polyamide resin is high, the amount of low-molecular-weight compounds such as monomers to be regenerated during remelting tends to increase. In order to cope with this problem, a polyamide to which a compound reacting with the carboxyl terminal or the amino terminal of the polyamide is added has been developed. Specifically, a method of reacting an organic glycidyl ester with a carboxyl group or an amino group of polyamide is proposed (JP 10-219104A). However, in this method, when the organic glycidyl ester and the polyamide chips are dry-blended and then melt-kneaded in an extruder, the organic glycidyl ester reacts with the terminal groups of the polyamide. In this method, it is difficult to mix the film uniformly in the dry-blending step before film formation. As a result, the composition varies, and it is difficult to obtain a polyamide having a uniform terminal group concentration. Furthermore, the dry blending process itself is not suitable for films with large melt extrusion amounts. In this method, the content of the low-molecular weight compound after melt molding is still large, and the reduction amount is insufficient.

On the other hand, a method of blocking the amino terminal of a polyamide resin with a dicarboxylic anhydride has been proposed (JP2005-187665 a). However, since the amount of the monomer to be regenerated during melting is still large, ranging from 0.27 to 0.75 mass%, it is difficult to sufficiently reduce the low molecular weight compound contained in the polyamide resin film.

In addition, a nylon 6 resin in which a piperidone compound is present in a state of being chemically bonded in a polymer chain or at a terminal has been proposed (JP 2001-081189A). The resin suppresses the generation of caprolactam due to melting under reduced pressure. However, in the film-forming step generally carried out under normal pressure, the oligomer produced when the resin is melted is difficult to be discharged out of the system, and therefore the oligomer reducing effect is insufficient.

As described above, various proposals have been made on low molecular weight compounds of polyamide resins. However, no reference has been made to a low molecular weight compound in a nylon product containing a polyamide (nylon MXD) containing xylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms as components.

Under such circumstances, particularly, a film made of nylon 6 or a mixed resin of nylon 66 and nylon MXD, or a film made of a multilayer laminate of these resins can be provided with further functionality with a film made of nylon 6 or nylon 66 resin, and therefore, is widely used as a gas barrier film, a linear cutting film, an easy-tear film, a shrink film, and the like.

However, the film containing nylon MXD has a problem in the production process or the processing process because the content of the low molecular weight compound is large. For example, the low molecular weight compound in the film is precipitated more to the outside of the film than in the nylon 6 resin film, and therefore improvement thereof is strongly desired.

As a measure for dealing with the deposition of low molecular weight compounds, a method for efficiently removing low molecular weight compounds such as monomers using warm water has been proposed in WO2008/075461a1 filed by the present applicant with respect to nylon 6 resin. However, this method cannot effectively remove a low molecular weight compound from a nylon resin product containing nylon MXD.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a biaxially stretched polyamide resin film which is excellent in productivity and performance, can be used for a package or container made of a polyamide resin, and contains nylon MXD, because the content of a low molecular weight compound in the film is greatly reduced without impairing the originally excellent properties, and thus there is no fear of defects occurring in the production process, the processing process, and the like of the film, and a method for producing the same.

In order to achieve the above object, a biaxially oriented polyamide resin film of the present invention comprises nylon 6 as a component 1 and a polyamide containing xylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms as a component 2, wherein the content of a low molecular weight compound in the biaxially oriented polyamide resin film is 0 to 0.2% by mass.

A method for producing a biaxially stretched polyamide resin film, wherein a biaxially stretched film produced by using a polyamide resin comprising nylon 6 as the 1 st component and a polyamide containing xylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms as the 2 nd component is contacted with water at 40 ℃ or higher and less than 70 ℃ for 1 to 10 minutes and further contacted with water at 70 ℃ or higher for 1 to 10 minutes at any stage in the production process of the biaxially stretched film.

According to the present invention, by performing the low molecular weight compound removal step on the polyamide resin film containing nylon MXD, the content of the low molecular weight compound in the film can be greatly reduced without impairing the excellent properties inherent in the polyamide resin film. Therefore, a biaxially oriented polyamide resin film which is excellent in productivity and performance and which can be used for packaging and containers made of a polyamide resin can be obtained.

Detailed Description

The present invention is described in detail below.

The biaxially stretched polyamide resin film is a biaxially stretched film comprising nylon 6 as the 1 st component and a polyamide (nylon MXD) containing xylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms as the 2 nd component.

The composition ratio of the 1 st component to the 2 nd component in the film-forming resin is preferably 95/5 to 30/70 in terms of mass ratio of the 1 st component/the 2 nd component. When the proportion of the component 1 exceeds 95% by mass, various properties derived from the component 2, such as barrier properties and flexibility, are not exhibited, or even if they are expressed slightly, it is difficult to obtain the effect obtained by adding the component 2. On the other hand, if the proportion of the 1 st component is less than 30% by mass, the toughness, which is characteristic of the 1 st component nylon 6, tends to be significantly impaired.

The content of the low molecular weight compound in the biaxially oriented polyamide resin film of the present invention is required to be 0 to 0.2 mass%. The content of the low molecular weight compound is preferably 0 to 0.1% by mass, more preferably 0 to 0.05% by mass or less, and most preferably 0% by mass.

If the content of the low-molecular weight compound exceeds 0.2 mass%, an oligomer as a low-molecular weight compound is precipitated on the film surface when the polyamide resin film is heated. Therefore, various problems occur in the production, processing, and the like. For example, when a large amount of low-molecular-weight compounds are precipitated, it is necessary to remove the low-molecular-weight compounds adhering to the production machine or the processing machine in order to prevent the occurrence of such a problem. For this reason, production activities or processing activities need to be suspended, significantly affecting production efficiency.

The smaller the content of the low-molecular weight compound, the better, but to reduce the content of the low-molecular weight compound, it is necessary to perform a low-molecular weight compound removal step for a long time during film formation, and productivity is deteriorated. Therefore, the lower limit is practically about 0.001 mass%.

In the present invention, the content of the low molecular weight compound in the polyamide resin film can be calculated by the following measurement method. That is, about 0.5g (converted to polyamide resin) of a film cut in a 0.5cm square was precisely weighed, extracted with 10 ml of distilled water in a boiling water bath (100 ℃) for 2 hours, and the content of a low molecular weight compound in the film was determined by liquid chromatography (for example, Hewlett Packard, HP100 HPLCsystem). More specific methods for use thereof are described below.

In the above, although the low molecular weight compounds detected in the case of the nylon 6 resin film were mainly caprolactam monomer and dimer, it was confirmed that the low molecular weight compounds detected in the mixture or the laminated film of nylon 6 and nylon MXD were not only caprolactam monomer and dimer. The low molecular weight compound referred to in the present invention means a component contained in a peak having the same elution time as that of the caprolactam monomer when measuring low molecular weight compounds such as monomers and dimers in the nylon 6 resin by HPLC.

According to the experiment of the present inventors, a low molecular weight compound contained in a mixed film or a laminated film of nylon 6 and nylon MXD was extracted and concentrated, and analyzed by IR (infrared spectroscopy) and NMR (nuclear magnetic resonance), and as a result, a peak derived from m-xylylenediamine was detected in the extracted low molecular weight compound. Further, mass analysis confirmed that there were many substances in the range of about 50 to 300 molecular weight of the low molecular weight component. As described above, in the polyamide resin containing nylon 6 and nylon MXD, not only caprolactam monomer and dimer but also a component containing m-xylylenediamine is present as a low molecular weight component. In order to remove low molecular weight components other than caprolactam, it is considered necessary to perform a removal treatment at a high temperature for a long time.

The biaxially stretched polyamide resin film of the present invention can be formed into a laminate film. The details thereof are as follows.

For example, in the dry lamination method, a stretched film or a sealant made of another resin is attached to a biaxially stretched polyamide resin film with an adhesive to form a laminated film suitable for packaging materials. In the extrusion method, a resin in a molten state is extruded at one time or more times onto the surface of a biaxially oriented polyamide resin film and laminated, or the resin is used as a substitute for an adhesive in extruding the resin to bond the film, whereby a laminate film suitable for use as a packaging material can be obtained.

The biaxially oriented polyamide resin film of the present invention contains nylon 6 and nylon MXD as main components, but may contain nylon 66, nylon 46, nylon 69, nylon 610, nylon 612, nylon 11, nylon 12, poly (m-xylylene adipamide) (nylon MXD6) or the like in an appropriate amount in the form of a mixture, copolymer or composite.

In order to suppress the generation of low molecular weight compounds at the time of melting, the polyamide resin constituting the biaxially oriented film more preferably contains an organic glycidyl ester, dicarboxylic anhydride, monocarboxylic acid such as benzoic acid, diamine, or the like as an end-capping agent.

The relative viscosity of the polyamide resin constituting the biaxially oriented film is not particularly limited, but is preferably 1.5 to 5.0 as measured at a temperature of 25 ℃ and a concentration of 1g/dL using 96% sulfuric acid as a solvent. More preferably 2.5 to 4.5, and still more preferably 3.0 to 4.0. Polyamide resins having a relative viscosity of less than 1.5 tend to significantly reduce the mechanical properties of the film. Further, a polyamide resin having a relative viscosity of more than 5.0 tends to hinder film formability of the film.

In the polyamide resin constituting the biaxially stretched film, 1 or 2 or more kinds of various additives such as a pigment, an antioxidant, an ultraviolet absorber, a preservative, an antistatic agent, an antiblocking agent, inorganic fine particles and the like can be added as necessary within a range not to adversely affect the properties of the film.

For the purpose of improving the slipperiness of the film, 1 or 2 or more kinds of various inorganic lubricants or organic lubricants may be blended in the polyamide resin constituting the biaxially oriented film. Examples of the lubricant include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, magnesium aluminosilicate, glass hollow sphere, carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, layered silicate, and ethylene bis stearamide.

The method for producing the biaxially oriented polyamide resin film of the present invention is as follows.

Briefly, for example, the biaxially oriented polyamide resin film of the present invention is obtained by heating and melting a polyamide resin composition with an extruder, extruding the composition into a film form from a T die, cooling and solidifying the composition on a rotating cooling drum by a known casting method such as an air knife casting method or an electrostatic application casting method to form an unstretched film, and subjecting the unstretched film to a stretching treatment. In melt extrusion, if a plurality of resins are mixed, a resin mixed film is obtained, and if a plurality of resins are simultaneously extruded from different nozzles and laminated, a multilayer film having a plurality of resin layers is obtained. If the unstretched film is oriented, the stretchability may be lowered in the subsequent step, and therefore, it is preferable that the unstretched film be substantially amorphous and in an unoriented state.

The stretching method includes sequential biaxial stretching in which a transverse stretching treatment is performed after longitudinal stretching, and simultaneous biaxial stretching in which a longitudinal stretching treatment and a transverse stretching treatment are performed simultaneously. In any of the stretching methods, it is preferable to perform the stretching treatment so that the surface magnification becomes 9 times or more so as to obtain a surface orientation coefficient of 0.05 or more.

The stretching method is not particularly limited, but a tenter-type biaxial stretching method in which a melt film formation step, a warm water pretreatment step, a low molecular weight compound removal step, a stretching step, a heat setting step, and a cooling step, which will be described later, can be performed in one step is effective and preferable.

The heat-fixing step is described as a step of heat-fixing the successively biaxially stretched or simultaneously biaxially stretched film at a temperature of 150 to 220 ℃ in a tenter subjected to stretching treatment, and if necessary, subjecting the film to relaxation treatment in the longitudinal and/or transverse directions in a range of 0 to 10%, preferably 2 to 6%.

In the production of the biaxially oriented polyamide resin film of the present invention, it is necessary to provide a step of removing the low molecular weight compound at an arbitrary stage in the above-mentioned film-forming step. In any stage, since the content of the low-molecular-weight compound increases when the polyamide resin is melted, the low-molecular-weight compound removal step is preferably performed after the polyamide resin is melted and molded into a film shape. The step of removing the low molecular weight compound may be performed at any stage of the unstretched film, the stage after longitudinal stretching, and the stage after biaxial stretching. However, it is preferable to carry out the process at a stage of an unstretched film in which the film is not crystallized or oriented, because the removal efficiency of the low molecular weight compound is good and the low molecular weight compound is not discharged to the atmosphere in the stretching step.

As described above, WO2008/075461a1 by the present applicant proposes a method for efficiently removing low molecular weight compounds such as monomers using warm water, with respect to a nylon 6 resin. However, the nylon resin film containing nylon 6 and nylon MXD has a larger content of low molecular weight substances than the nylon 6 resin film, and the effect of reducing the low molecular weight compounds is small only by the treatment described in WO2008/075461a 1. In the case of a nylon resin film containing nylon 6 and nylon MXD, the extraction efficiency of low molecular weight substances is low at low temperature of warm water. As a countermeasure, when the temperature of the hot water is increased, the film is wrinkled or loosened, which hinders the production of the film.

Therefore, in the present invention, after the pretreatment in the first water tank, the second water tank having a higher temperature is used, whereby the low molecular weight compounds in the film can be reduced without causing any trouble in the production process. Specifically, the removal step of the low molecular weight compound according to the present invention is a step of bringing a polyamide resin film into contact with water having a temperature of 40 ℃ or higher and less than 70 ℃ for 1 to 10 minutes under tension as a pretreatment, and then bringing the polyamide resin film into contact with hot water having a temperature of 70 ℃ or higher for 1 to 10 minutes.

In the step of removing the low molecular weight compounds, the water temperature in the first water tank as the hot water pretreatment tank needs to be 40 ℃ or higher and less than 70 ℃, preferably 50 ℃ or higher and less than 70 ℃, and more preferably 60 ℃ or higher and less than 70 ℃. The water temperature in the second water tank needs to be above 70 ℃. When the water temperature in the second water tank is less than 70 ℃, it is difficult to remove the low molecular weight compounds in a short time. Further, if the treatment is performed in the first water tank with hot water of 70 ℃ or higher, wrinkles are likely to be introduced into the film in the case of the treatment in the stage of the unstretched film, the stretching becomes nonuniform, the quality of the stretched film is reduced, and problems such as film breakage or film end portion pulling-up occur during the stretching, and the workability is deteriorated.

The pH of the water in the first and second water tanks is preferably 6.5 to 9.0. More preferably 7.0 to 8.5, and particularly preferably 7.5 to 8.0. When the pH is less than 6.5, oxidative deterioration of the polyamide resin film progresses. When the pH exceeds 9.0, alkaline water adheres to the membrane, and therefore the water is easily touched by an operator, and is not preferable in terms of safety.

Generally, in order to remove low molecular weight compounds, it is effective that the water temperature is high, but if the water temperature is raised, wrinkles are easily introduced in the unstretched film. If the temperature is set to a low water temperature, it takes time to remove the low molecular weight compound, and productivity is deteriorated. In contrast, by performing pretreatment in the first water tank as described in the present invention, it is possible to remove problematic low-molecular-weight compounds without causing wrinkles or sagging in the high-temperature second water tank and thereby reducing productivity.

In order to avoid problems during stretching when stretching is performed after the step of removing the low molecular weight compound, it is preferable that the unstretched polyamide resin film is stretched after the step of removing the low molecular weight compound and after the water content is adjusted to 1 to 10 mass%, preferably 4 to 8 mass%, by the water content adjusting step. When the water content is less than 1% by mass, the tensile stress increases, and the film is likely to be broken. Conversely, if the water content is more than 10 mass%, the thickness unevenness of the unstretched film increases, and the thickness unevenness of the obtained stretched film tends to increase.

After the treatment in the second water tank at a high temperature, the water content of the film is generally increased. Therefore, it is preferable to reduce the water content by bringing the film into contact with a roll having a water-absorbing layer, blowing dry air to the film, or the like. Conversely, when the water content is low, the water content can be adjusted using the water content adjusting tank. Pure water is generally used in the water adjustment tank. However, the treatment liquid may contain a dye, a surfactant, a plasticizer, and the like as needed. Further, the water content of the film may be adjusted by spraying steam to the film.

Various functions can be imparted to the biaxially stretched polyamide resin film of the present invention. The film may be subjected to an easy adhesion treatment for improving adhesion to other films, adhesives, inks, or the like, or may be subjected to an antistatic treatment for suppressing generation of static electricity, or may be coated with various functional coating liquids such as a barrier coating liquid for improving barrier properties. The coating method used for this is not particularly limited, and for example, a gravure roll method, a reverse roll method, an air knife method, a reverse gravure printing method, a Mayer Bar (Mayer Bar) method, a reverse roll method (invert roll) and the like can be used. Various coating methods and various spraying methods that are a combination of these methods can be used.

The thickness of the biaxially oriented polyamide resin film of the present invention is not particularly limited, but is preferably in the range of 10 to 30 μm when used for packaging.

The obtained biaxially stretched film may be subjected to a physical and chemical treatment such as corona discharge treatment, plating treatment, cleaning treatment, dyeing treatment, metal vapor deposition treatment, and various coating treatments as needed.

The biaxially stretched polyamide resin film of the present invention can be used as a heat-sealable packaging material by laminating it with a sealant layer such as polyolefin by, for example, dry lamination or extrusion to form a laminate film.

Examples

Next, the present invention will be described in detail by examples. The evaluation methods of various physical properties in the following examples and comparative examples are as follows.

(1) Content of low molecular weight compound in film

Adjustment of measurement sample

About 0.5g of a film cut into a 0.5cm square was precisely weighed, and the film was placed in a 10-ml headspace bottle, 10 ml of distilled water was added, the bottle was sealed with a butyl rubber stopper and an aluminum cap, and then extracted in a boiling water bath (100 ℃ C.) for 2 hours. Then, the sample was cooled and filtered through a 0.45 μm disk filter to prepare a sample for measurement.

Correction Curve

Caprolactam is used as a reference substance for the quantification of low molecular weight compounds. 0.1g of caprolactam was dissolved in 100 ml of distilled water and further diluted to prepare a standard solution of 100 ppm. Then, 1-10 microliters of each solution was injected to obtain a calibration curve.

Conditions for HPLC

The device comprises the following steps: HP1100HPLC system manufactured by Hewlett Packard Co., Ltd

Column: waters Pureseil 5. mu.C 1820 nm (200. ANG.) 4.6mm X250 mm (40 ℃ C.)

A detector: UV210nm

The elution was carried out for 12 minutes with 35/75 v/v as the eluent, followed by 3 minutes for 100/0 v/v and 20 minutes for 35/75 v/v as the eluent.

Flow rate: 0.7 ml/min.

Sample introduction amount: 10 microliter (50 microliter sample with low concentration)

Detection limit: 3ppm of

Method of calculation

The mass of the low-molecular weight compound in the sample was calculated by obtaining the concentration of the low-molecular weight compound in the sample under the above-mentioned conditions, and the mass was divided by the mass of the film to obtain a value of the content (mass%) of the low-molecular weight compound.

(2) Uneven thickness

The thickness was measured at intervals of 10cm across the entire width of a stretched film having a width of 300cm using a β -ray transmission type thickness gauge (manufactured by Fuji electric Co., Ltd., model TG-220), and the value given by the following equation was taken as the thickness unevenness. The thickness unevenness was evaluated on the following 3 scales of "∘", ". DELTA" and ". times", and the thickness unevenness was not more than 15%, i.e. "· and". DELTA "were acceptable.

Thickness unevenness (maximum thickness in width direction-minimum thickness in width direction) ÷ average thickness × 100

O: the thickness is not all below 10%

And (delta): the thickness of the film is not more than 10% but less than 15%

X: the thickness unevenness is more than 15 percent

(3) Operability of

The state of the unstretched film passing through the warm water tank was visually observed to determine the occurrence of wrinkles, snaking, and the like. When no wrinkles, meandering or the like occurred, the workability was good, and the evaluation was "o". When wrinkles, meandering and the like occurred, the workability was poor, and the evaluation was "x".

The raw materials used in the following examples and comparative examples are as follows.

Nylon 6

100 parts by mass of epsilon-caprolactam, 0.12 part by mass (10 mmol/kg per epsilon-caprolactam) of benzoic acid and 3 parts by mass of water were put into a closed reaction vessel equipped with a stirrer, and the temperature was raised. Then, polycondensation reaction was carried out at a pressure of 0.5MPa and a temperature of 260 ℃. Next, the reaction product was taken out from the vessel, and then cut into a chip shape, which was refined and dried to obtain nylon 6 resin chips. The cut piece had a terminal carboxyl group of 46mmol/kg, a terminal amino group of 36mmol/kg and a relative viscosity of 3.03.

Main slice (master chip)

A master chip was prepared by melt-mixing 6 parts by mass of silica (サイロイド SY-150: manufactured by Shuizui chemical Co., Ltd.) per 100 parts by mass of nylon 6 resin.

Nylon MXD

Commercially available "MX nylon 6007 (manufactured by mitsubishi gas chemical corporation, which contains xylylenediamine and adipic acid as an aliphatic dicarboxylic acid having 6 carbon atoms)" was used as a resin pellet.

Example 1

Nylon 6 resin and the above-described main chip were mixed so that the mixing ratio of silica was 0.05 mass%, to obtain nylon 6 resin chips. The nylon 6 resin chips/nylon MXD resin chips were mixed at a mass ratio of 80/20, and charged into an extruder having a coat hanger type T die and a diameter of 65 mm. Then, the film was melted in a cylinder heated to a temperature of 270 ℃ and then extruded, and the film was closely adhered to a rotary drum cooled to 20 ℃ and rapidly cooled, thereby obtaining an unstretched film having a thickness of 160 μm.

Next, the unstretched film was introduced into a hot water pretreatment tank as a first hot water tank in which the water temperature was set to 60 ℃, and immersed in water for 1 minute as a hot water pretreatment step. Thereafter, the mixture was introduced into a hot water treatment tank having a water temperature of 90 ℃ as a second warm water tank, and immersed in water for 1 minute as a step of removing low molecular weight compounds. Then, the unstretched film having absorbed water was guided to a simultaneous biaxial stretching machine, and simultaneous biaxial stretching was performed at a magnification of 3.3 times the length and 3.3 times the width. Subsequently, the stretched film was subjected to a heat treatment at a temperature of 210 ℃ to thereby perform a relaxation treatment of 5% in the transverse direction, thereby obtaining a biaxially stretched polyamide resin film having a thickness of 15 μm. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

TABLE 1

As shown in table 1, the biaxially stretched polyamide resin film of example 1 had a small content of a low molecular weight compound.

Further, the infrared spectroscopic analysis method (Perkin Elmer System 2000KBr method) and the nuclear magnetic resonance analysis method (JEOL, Lambada300WB NMR,¹H) When the low-molecular-weight compound extracted from the film was analyzed, a peak of m-xylylenediamine derived from nylon MXD as a constituent molecule was observed. In mass analysis (GC-MS, UA5-30M-0.25F, helium 1.0ml/min., split ratio 30: 1, 70 → 320 ℃, mass range 5-500), a plurality of molecular weights of 50-300 were observed. From the above, it is considered that the components of the low molecular weight compound are various low molecular weight compounds containing not only caprolactam and cyclic dimer derived from nylon 6 but also m-xylylenediamine derived from nylon MXD.

Example 2

The hot water treatment time was set to 5 minutes. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 3

The hot water treatment time was set to 10 minutes. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 4

The hot water treatment temperature was set to 70 ℃. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 5

The warm water pretreatment time was set to 5 minutes. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 6

The warm water pretreatment time was set to 10 minutes. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 7

The warm water pretreatment temperature was set to 40 ℃. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 8

The warm water pretreatment was set to 69 ℃ for 3 minutes, and the hot water treatment was set to 80 ℃ for 1 minute. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 9

The nylon 6 resin chip/nylon MXD resin chip was set to a mass ratio of 90/10. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 10

Nylon 6 resin chips/nylon MXD resin chips were mixed in a mass ratio of 60/40. The warm water pretreatment was set to 50 ℃ for 3 minutes, and the hot water treatment was set to 70 ℃ for 5 minutes. Except for this, a biaxially oriented polyamide resin film was obtained in the same manner as in example 1. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Example 11

Nylon 6, nylon MXD, and equal amounts of nylon 6 and nylon MXD were melt extruded separately from the extruder using a five-layer co-extrusion T die, overlapping in the order nylon 6/equal amount mixture/nylon MXD/equal amount mixture/nylon 6. The laminate was rapidly cooled while being closely adhered to a cooling drum whose surface temperature was adjusted to 20 ℃ to obtain an unstretched multilayer sheet having a thickness of 150 μm.

Then, a biaxially oriented polyamide resin film having a five-layer structure and a thickness of 15 μm was obtained in the same manner as in example 2. The thickness of the five-layer film was 4.5/0.5/5.0/0.5/4.5[ mu ] m. The content ratio of nylon 6 to nylon MXD in the five-layer film was 95/55 in terms of mass ratio. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented polyamide resin film are shown in table 1.

Comparative example 1

The hot water treatment time was set to 0.5 minutes as compared with example 1. Otherwise, the same procedure as in example 1 was carried out. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Since the time of the step of removing the low molecular weight compound is too short, the content of the low molecular weight compound in the obtained stretched film is large.

Comparative example 2

The hot water treatment time was set to 15 minutes, which is longer than that in example 3. Otherwise, the same procedure as in example 3 was carried out. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Although the hot water treatment time is prolonged, the content of the low molecular weight compound is not improved significantly, and the hot water treatment time is prolonged, so that the production efficiency is lowered.

Comparative example 3

The hot water treatment temperature was reduced to 60 ℃ compared to example 2. Otherwise, the same procedure as in example 2 was carried out. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Since the water temperature in the hot water treatment step is too low, the content of low molecular weight compounds is large.

Comparative example 4

The time for the warm water pretreatment was set to 20 minutes as compared with example 1. Otherwise, the same procedure as in example 1 was carried out. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Although the time for the pretreatment of the warm water is lengthened, the content of low molecular weight compounds is only slightly reduced. However, since the warm water pretreatment time is long, the operability is deteriorated and the production efficiency is remarkably lowered.

Comparative example 5

The temperature of the warm water pretreatment was set to 30 ℃ as compared with example 5. Otherwise, the same procedure as in example 5 was repeated. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Since the temperature of the hot water pretreatment is too low, wrinkles are often generated in the obtained stretched film to cause thickness unevenness, and the workability is remarkably lowered. The low molecular weight compounds cannot be sufficiently removed.

Comparative example 6

The temperature of the warm water pretreatment was set to 80 ℃ as compared with example 1. Otherwise, the same procedure as in example 1 was carried out. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Since the temperature of water in the warm water pretreatment is too high, the resulting stretched film often wrinkles, and the film cannot be stably produced.

Comparative example 7

Compared with example 1, the warm water pretreatment process was omitted. Otherwise, the same procedure as in example 1 was carried out. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Since the warm water pretreatment process is omitted, wrinkles are generated on the film, stretching becomes uneven, and the film cannot be stably produced.

Comparative example 8

The step of removing the low molecular weight compound in the second warm water tank was omitted as compared with example 11. The water temperature in the hot water pretreatment step in the first hot water tank was set to 70 ℃. Otherwise, the same operation as in example 11 was performed. The results of evaluation of the low molecular weight compound content, thickness unevenness, and handling properties of the obtained biaxially oriented film are shown in table 1.

Since the hot water treatment step as the low molecular weight compound removal step is not performed, the content of the low molecular weight compound in the stretched film becomes a high value.

Claims (9)

1. A biaxially stretched polyamide resin film, wherein,

the biaxially oriented polyamide resin film comprises a nylon 6 as a component 1 and a polyamide containing xylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms as a component 2,

the composition ratio of the 1 st component to the 2 nd component is 95/5-30/70 in terms of mass ratio,

the biaxially oriented polyamide resin film contains a low-molecular-weight compound in an amount of 0 to 0.2 mass%.

2. The biaxially stretched polyamide resin film according to claim 1, wherein the content of the low molecular weight compound is 0 to 0.1% by mass.

3. The biaxially stretched polyamide resin film according to claim 1, wherein the relative viscosity of the polyamide resin measured at a temperature of 25 ℃ and a concentration of 1g/dL using 96% sulfuric acid as a solvent is 1.5 to 5.0.

4. The biaxially oriented polyamide resin film according to claim 1, which contains a terminal-blocking agent.

5. The biaxially stretched polyamide resin film according to claim 1, which contains a lubricant.

6. A method for producing a biaxially stretched polyamide resin film, wherein, at any stage in the production process of a biaxially stretched film using a polyamide resin comprising nylon 6 as the 1 st component, a polyamide containing xylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms as the 2 nd component, the film is contacted with water having a temperature of 40 ℃ or higher and less than 70 ℃ for 1 to 10 minutes, and further contacted with water having a temperature of 70 ℃ or higher for 1 to 10 minutes,

the composition ratio of the 1 st component and the 2 nd component is 95/5-30/70 in terms of mass ratio of the 1 st component/the 2 nd component.

7. A laminate film comprising the biaxially stretched polyamide resin film according to claim 1.

8. A packaging material comprising the biaxially stretched polyamide resin film according to claim 1.

9. The packaging material according to claim 8, wherein the biaxially oriented polyamide resin film has a thickness in the range of 10 μm to 30 μm.