JP2003020349A - Polyamide film and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide film which exhibits a low moisture-absorption elongation in a high-humidity atmosphere and is excellent in clarity; and a production method for the film. SOLUTION: A resin composition comprising 99.9-99.0 mass% polyamide resin and 0.1-1.0 mass% layered silicate homogeneously dispersed therein is melt-formed into an unstretched film, which is subjected to successive or simultaneous biaxial stretching; thus is prepared a polyamide film of which the moisture-absorption elongation in the transverse direction after the change of atmospheric humidity at 20 deg.C from 40%RH to 80%RH is 1.3% or lower and which has a haze of 5.0% or lower and a plane orientation coefficient of 0.05 or higher.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyamide film and a method for producing the same. In particular, the present invention relates to a polyamide film having a low hygroscopic elongation in a high humidity atmosphere, excellent transparency and mechanical strength, and a method for producing the same.

[0002]

2. Description of the Related Art Biaxially stretched polyamide films are excellent in impact resistance, abrasion resistance, pinhole resistance, etc., including mechanical properties, optical properties, thermal properties and gas barrier properties. Therefore, it is widely used as a film for packaging materials such as foods. The polyamide film is rarely used as a single film, and is usually used after being printed or laminated.

By the way, since the polyamide film has a high hygroscopic property due to the molecular structure of the polyamide resin, a dimensional change due to moisture absorption, so-called "hygroscopic elongation" is likely to occur, and in the processing of the film, especially in the lateral direction (TD direction). The hygroscopic elongation of is likely to occur. When such hygroscopic elongation occurs, many hygroscopic wrinkles are contained in the surface layer of the product and the surface layer becomes unusable.Therefore, it is necessary to lengthen the winding length, that is, to increase the so-called "entrance", which results in high cost. Becomes Further, when multi-step printing is performed on a product, if the dimensional change due to moisture absorption is large, there is a problem that a phenomenon called "print pitch shift" in which printed patterns are displaced is likely to occur.

Further, such a printing film is usually laminated for bag making and the like, but it is rarely done immediately after printing for convenience of work, and it is left for a while after printing. After that, a laminating process is generally performed. Therefore, excessive hygroscopic elongation occurs during leaving, and in the case of dry lamination,
When the adhesive is applied with a gravure roll or the like, a problem occurs such that a desired width cannot be applied.

As a method for controlling the moisture absorption elongation, for example,
Japanese Unexamined Patent Publication No. 8-197619 discloses that when an amorphous unstretched polyamide film is sequentially biaxially stretched, it is MD (longitudinal) stretched in two steps and then TD (transverse) stretched, and its temperature is controlled. Then, a method of reducing the drawing stress and reducing the pattern distortion due to moisture absorption has been proposed. However, this method has a problem that the relaxation rate becomes large during the heat treatment performed after the successive biaxial stretching, and finally the hygroscopic elongation also becomes large.

Further, in JP-A-4-173229, after unstretched polyamide film is TD stretched and MD stretched, TD relaxing and heat fixing, MD relaxing and heat fixing are performed, and subsequently heat fixing is performed under steam. That method has been proposed. However, this method has complicated steps,
There is a problem that a stable quality polyamide film cannot be obtained.

In order to solve such a problem, in Japanese Patent Laid-Open No. 2000-26627 or the like, a polyamide using as a main component an aromatic polyamide resin having a lower hygroscopicity than an aliphatic polyamide resin is used as a main component. Although a film has been proposed, the above-mentioned problem cannot be solved yet with a structure containing an aliphatic polyamide as a main component such as nylon 6, which is widely used as a biaxially stretched film at present. Further, the above-mentioned polyamide film is mainly composed of an aromatic polyamide resin having poor mechanical properties such as flex fatigue resistance, so that the performance is improved by blending a flex fatigue resistance improver. There is a problem that it is clearly inferior to a film containing an aliphatic polyamide as a main component such as nylon 6.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a polyamide film having a low hygroscopic elongation in a high humidity atmosphere, excellent transparency and mechanical strength, and a method for producing the same. It is a thing.

[0009]

The inventors of the present invention have achieved the present invention as a result of extensive studies to solve the above problems. That is, the present invention relates to polyamide resin 99.
Layer silicate 0.1 to 1.0% by mass in 9 to 99.0% by mass
Is a film composed of a resin composition in which are uniformly dispersed, at 20 ° C., 40% RH, and 20 ° C., 80% R
The moisture absorption elongation in the TD direction when the humidity is changed to an H atmosphere is 1.3% or less, the haze is 5.0% or less, and the plane orientation coefficient is 0.05 or more. The main point is a polyamide film.

As described above, by uniformly dispersing the layered silicate in the polyamide resin at a predetermined ratio to increase the plane orientation coefficient, the mechanical strength is excellent, and the change in the hygroscopic elongation in a high humidity atmosphere is suppressed. A polyamide film that is small and has excellent transparency can be obtained, and printability and laminating processability can be improved. Further, when the layered silicate is dispersed in the polyamide resin to increase the plane orientation coefficient, the haze tends to increase, but in the present invention, by adopting the following manufacturing method, the haze is suppressed and the transparency is excellent. A polyamide film can be obtained.

As a method of biaxially stretching a polyamide resin, there are a sequential biaxial stretching in which a longitudinal stretching treatment is performed and then a transverse stretching treatment, and a simultaneous biaxial stretching in which a longitudinal and transverse stretching treatment is simultaneously performed. Then, the manufacturing conditions are made different between the sequential biaxial stretching and the simultaneous biaxial stretching.

That is, in the case of successive biaxial stretching, a resin composition in which 0.1 to 1.0% by mass of layered silicate is uniformly dispersed in 99.9 to 99.0% by mass of polyamide resin is prepared by melting. After film formation and stretching of this unstretched film in the machine direction, the film temperature (T
i) in the range of Tg ≦ Ti ≦ Tcp, and the film temperature (Te) at the maximum stretching ratio point at which the transverse stretching ratio becomes maximum is T
A gist of the method for producing a polyamide film is that the film is stretched in the transverse direction in the range of m-70≤Te≤Tm, and the film is formed by the successive biaxial stretching. Here, Tg is the glass transition temperature of the polyamide resin,
Tcp is the crystallization peak temperature of the polyamide resin, and Tm is the melting point of the polyamide resin.

In the case of simultaneous biaxial stretching, a layered silicate of 0.1 is added to the polyamide resin of 99.9 to 99.0 mass%.
~ 1.0% by mass of the resin composition uniformly dispersed is melt-cast into a film, and the unstretched film has a film temperature (Ti) within a range of Tg ≤ Ti ≤ Tcp until the surface magnification reaches 4 times. The method for producing a polyamide film is characterized in that the film temperature (Te) at the maximum draw ratio point at which the areal magnification becomes maximum is Tm-70 ≤ Te ≤ Tm, and the film is simultaneously biaxially drawn to form a film. It is what Here, Tg is the glass transition temperature of the polyamide resin, Tcp is the crystallization peak temperature of the polyamide resin, and Tm is the melting point of the polyamide resin.

As described above, the polyamide resin composition containing the layered silicate in a specific ratio is sequentially or biaxially stretched under specific conditions to suppress the hygroscopic elongation in a high humidity atmosphere, A polyamide film having high mechanical strength and excellent transparency can be easily manufactured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polyamide film of the present invention is
It is necessary for the resin composition to have a layered silicate of 0.1 to 1.0% by mass uniformly dispersed in a polyamide resin of 99.9 to 99.0% by mass. When the blending ratio of the layered silicate is less than 0.1% by mass, the obtained film has a high hygroscopic elongation and poor dimensional stability. Further, when the mixing ratio of the layered silicate is more than 1.0% by mass, the haze of the film becomes high and the transparency becomes poor. In particular, when the surface orientation coefficient is increased to improve the strength performance of the film as in the present invention, this blending ratio is an important requirement.

A film made of this resin composition can be used at 20 ° C. and 80% R under 20 ° C. and 40% RH atmosphere.
It is necessary that the hygroscopic elongation in the TD direction is 1.3% or less when the humidity is changed to the H atmosphere. When the hygroscopic elongation in the TD direction when the humidity is changed exceeds 1.3% in this way, a print pitch shift occurs during printing of this film, resulting in poor printability. As a result, dimensional change easily occurs, and good lamination cannot be performed.

The polyamide film of the present invention must have a plane orientation coefficient of 0.05 or more. The plane orientation coefficient affects the mechanical strength of the film,
By setting the plane orientation coefficient to be 0.05 or more as in the present invention, the strength performance is equal to or more than that of a polyamide biaxially stretched film which has been conventionally marketed for packaging and the like, specifically, a stretched film having a thickness of 15 μm. In the case of, it is possible to give a puncture strength of 10 N or more. If the plane orientation coefficient is less than 0.05, the mechanical strength is inferior, and problems such as bag breakage are likely to occur when used for packaging applications, making it unsuitable for actual use. Therefore, the plane orientation coefficient is more preferably 0.055 or more. In order to make the plane orientation coefficient of 0.05 or more, as described later, when the unstretched film prepared by melting the above resin composition is stretched, the stretching ratio is 9 times in terms of the surface magnification. It is necessary to make it above. This is the same for both sequential biaxial stretching and simultaneous biaxial stretching.

Further, the polyamide film of the present invention must have a haze of 5.0% or less. When the haze exceeds 5.0%, the transparency of the film is deteriorated and the appearance of printing is deteriorated. Usually, since the film is required to have slipperiness, the haze of the film is generally in the range of 3 to 5% because fine particles such as silica are added. If these fine particles are not added, the haze can be made lower, but the slipperiness deteriorates, and processing such as printing and laminating becomes impossible. Further, as in the present invention, a layered silicate is added, and
The deterioration of transparency when the surface orientation coefficient is increased is due to non-uniform void formation, so unlike the deterioration of transparency due to the addition of a lubricant such as silica, a remarkable poor appearance (unevenness) may occur. Becomes Note that this is not the case when an inorganic substance such as a white pigment or another polymer is mixed to intentionally deteriorate the transparency of the film due to special decorative requirements.

As the polyamide resin constituting the polyamide film of the present invention, those containing an aliphatic polyamide as a main component can be preferably used. As the aliphatic polyamide, a lactam having three or more members, a polymerizable ω-amino acid,
Polyamide resin obtained by polycondensation of dibasic acid and diamine, specifically, ε-caprolactam, aminocaproic acid, enanthlactam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid,
Polymers such as α-pyrrolidone and α-piperidone, diamines such as hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, and dodecamethylenediamine, and dicarboxylic acids such as adipic acid, sebacic acid, dodecane dibasic acid, and glutaric acid. Examples thereof include polymers obtained by polycondensing a salt of with or copolymers thereof. Among them, nylon 4, nylon 6, nylon 7, nylon 8,
Nylon 11, Nylon 12, Nylon 66, Nylon 610, Nylon 611, Nylon 612, Nylon 6
/ 66, nylon 6/12 and the like can be preferably used, and in particular,
A polymer containing nylon 6 or nylon 66 as a main component can be more preferably used because of its excellent mechanical properties and thermal properties, and nylon 6 is most suitable. As long as the effects of the present invention are not significantly impaired, aromatic components such as metaxylylenediamine, terephthalic acid and isophthalic acid are copolymerized, and aromatic compounds such as nylon 6T, nylon 6 / 6T and nylon 6I / 6T are used. Polyamide may be added.

The relative viscosity of the polyamide resin is not particularly limited, but 98% by mass concentrated sulfuric acid is used as a solvent, and the temperature is 25
The relative viscosity measured under the conditions of 1 ° C. and a concentration of 1 g / dl is 1.
Those in the range of 5 to 5.0 are preferable. When the relative viscosity is less than 1.5, the mechanical performance of the film is lowered, and when the relative viscosity is more than 5.0, the film formability is lowered.

The layered silicate used in the present invention includes:
Examples include smectite clay minerals such as montmorillonite, beidellite, saponite, nontrolite, hectorite, and stevensite, vermiculite clay minerals, halloysite clay minerals, and the like. These layered silicates may be natural or synthetic, and examples of the synthetic ones include swelling fluoromica-based minerals. Above all, the layer thickness is 6
.About.12 .ANG., And the length of one side of the layer is preferably 0.001 to 10 .mu.m.

In order to obtain a resin composition in which the layered silicate is uniformly dispersed in the above polyamide resin, the layered silicate is contacted with a swelling agent, for example, 12-amidododecanoic acid, and the interlayer of the layered silicate is preliminarily prepared. Is spread so that the monomer can be easily taken in between the layers, and then it is mixed with the polyamide monomer and polymerized.

Further, the resin composition constituting the polyamide film of the present invention may be a lubricant, an antistatic agent, an antiblocking agent, a plasticizer, a colorant, a release agent, a pigment, etc., as long as the characteristics thereof are not significantly impaired. The above additives may be added, and these are added at the time of melt-kneading or polymerization of the resin composition.

The polyamide film configured as described above is manufactured by the following method. The polyamide film of the present invention is obtained, for example, by heating and melting a resin composition in which a layered silicate is uniformly dispersed in a polyamide resin in the above-mentioned mixing ratio with an extruder and extruding it into a film form from a T-die by an air knife casting method. It can be obtained by cooling and solidifying on a rotating cooling drum by a known casting method such as the electrostatic impression casting method to form an unstretched film, and subjecting this unstretched film to a stretching treatment. If the unstretched film is oriented, the stretchability may be deteriorated in a later step. Therefore, the unstretched film is preferably in a substantially amorphous and non-oriented state.

The stretching treatment includes sequential biaxial stretching in which stretching is carried out in the longitudinal direction and then in the transverse direction, and simultaneous biaxial stretching in which stretching is carried out simultaneously in the longitudinal and transverse directions. In the present invention, sequential biaxial stretching is carried out. The production conditions are different between the case of performing the simultaneous biaxial stretching and the case of performing the simultaneous biaxial stretching.
In order to obtain the above surface orientation coefficient, it is necessary to perform stretching treatment so that the surface magnification becomes 9 times or more.

Sequential biaxial stretching is performed as follows. First, the unstretched film is preheated for stretching the film, and is longitudinally stretched by using a roller type longitudinal stretching machine including heating roller groups having different peripheral speeds. The heating roller group of the longitudinal stretching machine is set so as to have a temperature not lower than the glass transition point of the unstretched film, and the longitudinal stretching ratio between the heating stretching roll and the cooling roll for cooling the film is 2.6. It is preferable to perform the longitudinal stretching treatment so that the stretching ratio is about 3.2 times.

Next, after preheating the film for stretching with a tenter type transverse stretching machine, the transverse stretching treatment is carried out. In the present invention, the film temperature Ti is Tg≤Tg until the transverse stretching ratio reaches 2. The range of Ti ≦ Tcp is set, and the transverse stretching ratio is 2
It is necessary to set the film temperature Te at the time when the stretching ratio exceeds the maximum to reach the maximum draw ratio in the range of Tm-70 ≦ Te <Tm. Here, Tg is the glass transition temperature of the polyamide resin,
Tcp is the crystallization peak temperature of the polyamide resin, and Tm is the melting point of the polyamide resin.

When the film temperature Ti until the transverse stretching ratio reaches 2 times is lower than the glass transition temperature Tg, the initial stretching stress (yield point stress) becomes high, and necks and voids are generated in the film to cause initial cutting. Occur. Even if the film can be stretched, if the film temperature becomes high after the transverse stretching ratio exceeds 2, the film will be whitened and the appearance will be poor. On the contrary, the film temperature Ti until the transverse stretching ratio reaches 2 times is the crystallization peak temperature Tcp of the polyamide resin.
If the value is higher than the above value, crystallization is promoted at the stage of elastic deformation of the film, which induces film whitening, resulting in poor appearance and frequent film breakage due to film whitening, resulting in a significant decrease in operability. To do. Film temperature Te when the transverse stretching ratio exceeds 2 times and reaches the maximum stretching ratio
However, when it is lower than Tm-70, film breakage and deterioration of operability occur, and when the film temperature Te is Tm or higher, the hygroscopic elongation becomes large, probably because the crystal structure that reduces the hygroscopic elongation is destroyed. If Te greatly exceeds Tm, the film itself melts and breaks. Further, when the stretching treatment at the film temperature Ti is completed before the transverse stretching ratio is less than 2 times and the stretching treatment is switched to the film temperature Te, elastic deformation preferentially proceeds, and the ratio of plastic deformation is still present. Is supplied to the subsequent stretching process at a high temperature in a small state, voids are generated in the film of the elastically deformed portion and whitening occurs. On the contrary, when the stretching treatment at the film temperature Ti is performed until the transverse stretching ratio exceeds 2 times, an effect of suppressing the hygroscopic elongation of the film and improving transparency is exhibited in the stretching treatment at the film temperature Te. Disappear. Therefore, when the stretching ratio exceeds 2 times, the film temperature Te is quickly changed to T
It is desirable to raise the range to m-70 ≦ Te <Tm.

As described above, until the transverse stretching ratio reaches 2, the film temperature Ti is controlled between the glass transition temperature of the polyamide resin and the crystallization peak temperature so that plastic deformation is preferentially promoted to cause elastic deformation. By reducing the ratio, it is possible to reduce the stretching stress and suppress the occurrence of voids in the elastically deformed portion after the transverse stretching ratio exceeds 2. Further, when the transverse stretching ratio exceeds 2 times and reaches the maximum stretching ratio, the film temperature can be made higher than the crystallization temperature to promote the crystallization of the film and reduce the hygroscopic elongation. The elastic deformation ratio can be lowered by increasing the plastic deformation ratio in the film. As a result, a film having low hygroscopic elongation and excellent transparency can be produced with high operability. Further, in the present invention, in addition to the above-mentioned constitution, since the layered silicate is uniformly dispersed in the resin composition forming the film, the crystallization of the polyamide resin is further promoted, and as a result, in a high humidity atmosphere. It is possible to reduce the hygroscopic elongation and improve the transparency.

On the other hand, the simultaneous biaxial stretching is carried out as follows. First, the unstretched film is preheated for stretching the film, and is stretched simultaneously in the longitudinal and lateral directions using a tenter type simultaneous biaxial stretching machine. In the present invention, the film temperature Ti is set in the range of Tg ≦ Ti ≦ Tcp until the surface magnification reaches 4 times,
Film temperature T at the maximum draw ratio point where the surface magnification becomes maximum
It is necessary to set e within the range of Tm−70 ≦ Te ≦ Tm.
Here, Tg is the glass transition temperature of the polyamide resin, Tc
p is the crystallization peak temperature of the polyamide resin, and Tm is the melting point of the polyamide resin.

Film temperature T until the areal magnification reaches 4 times
When i is lower than the glass transition temperature Tg, the initial stretching stress (yield point stress) becomes high, and a neck or a void is generated in the film to cause initial cutting. Further, even if the film can be stretched, if the film temperature rises after the areal magnification exceeds 4, the film will be whitened and the appearance will be poor. On the contrary, the film temperature Ti until the surface magnification reaches 4 times Ti
Is higher than the crystallization peak temperature Tcp of the polyamide resin, crystallization proceeds at the stage where the film is elastically deformed, which induces film whitening, which not only deteriorates the appearance but also causes film breakage due to film whitening. Frequently occurs and the operability is significantly reduced. If the film temperature Te is lower than Tm-70 when the surface magnification exceeds 4 times and becomes the maximum surface magnification, film breakage occurs and the operability is lowered, and the film temperature Te exceeds the melting point Tm of the polyamide resin. When,
Perhaps because the crystal structure that reduces the hygroscopic elongation is destroyed, the hygroscopic elongation increases, and when the film temperature Te greatly exceeds Tm, the film itself melts and breaks. Moreover, if the stretching treatment at the film temperature of Ti is completed before the surface magnification is less than 4 times and the stretching treatment at the film temperature is changed to Te, the elastic deformation is preferentially progressed and the ratio of the plastic deformation still remains. Is supplied to the subsequent stretching treatment at a high temperature in a small state, a void is generated in the film of the elastically deformed portion and whitening occurs. Further, when the stretching treatment with the film temperature Ti is performed until the surface magnification exceeds 4 times, the effect of suppressing the hygroscopic elongation of the film and improving the transparency is not exhibited in the stretching treatment with the film temperature Te. . Therefore, when the surface magnification exceeds 4 times, the film temperature Te is promptly changed to Tm-
It is desirable to raise the range to 70 ≦ Te ≦ Tm.

As described above, the simultaneous biaxial stretching treatment controls the film temperature Ti between the glass transition temperature Tg of the polyamide resin and the crystallization peak temperature Te until the surface magnification reaches 4 times, giving priority to plastic deformation. It is possible to reduce the stretching stress and suppress the generation of voids in the elastically deformed portion after the surface magnification exceeds 4 times by progressively advancing the elastic deformation to reduce the elastic deformation ratio. Further, when the areal ratio exceeds 4 times and reaches the maximum draw ratio, the film temperature can be set to be higher than the crystallization temperature to promote the crystallization of the film, and the hygroscopic elongation can be reduced. By performing stretching deformation, the plastic deformation rate in the film can be further increased and the elastic deformation rate can be lowered. As a result, a film having low hygroscopic elongation and excellent transparency can be produced with high operability. Further, in the present invention, in addition to the above configuration, since the layered silicate is dispersed in the resin composition forming the film, crystallization of the polyamide resin is further promoted, and as a result, hygroscopic elongation in a high humidity atmosphere Can be reduced and transparency can be improved.

As described above, the temperature control during the sequential biaxial stretching or the simultaneous biaxial stretching is performed by gradually increasing the air volume in one film stretching direction in the film advancing direction.
Further, the stretched portion may be divided into two or more zones for individual temperature control, or these may be applied in combination.

The film that has been sequentially biaxially stretched or simultaneously biaxially stretched as described above is
Heat set at a temperature of 50 to 220 ° C, and 0 to 1 if necessary.
The relaxation treatment in the longitudinal direction and / or the transverse direction is performed in the range of 0%, preferably 2 to 6%.

When the polyamide film of the present invention is used as a general packaging material excluding shrink film and the like, it is required to have thermal dimensional stability and wet heat dimensional stability. The following is preferably 3.
It is required to be 5% or less. The hot water shrinkage decreases as the temperature increases and the relaxation treatment increases. Therefore, it is necessary to appropriately finely adjust the temperature and the relaxation treatment so as to obtain a desired hot water shrinkage.

Subsequently, the stretched film was once released from the clip, and the unstretched residue at the end was trimmed.
It is wound up as a raw roll, separately slit into a desired width with a slitter, and wound up as a product.

The polyamide film of the present invention contains
In order to impart functionality, various functional coating liquids may be applied. The coating is usually applied to the film immediately before or after transverse stretching in the case of sequential biaxial stretching, or to the film immediately before or after stretching in the case of simultaneous biaxial stretching. The coating method is not particularly limited, and examples thereof include a gravure roll method, a reverse roll method, an air knife method, a reverse gravure method, a Meyer bar method, an inverse roll method, or various coating methods by a combination thereof or various spray methods. A method etc. can be adopted.

As described above, according to the present invention, by using a resin composition in which a layered silicate is uniformly dispersed in a polyamide resin at a specific ratio, a stretching treatment is performed under specific conditions.
A polyamide film having excellent mechanical strength and transparency and having a small moisture absorption change rate even in a high humidity atmosphere can be stably manufactured with high operability.

[0039]

EXAMPLES Next, the present invention will be described more specifically by way of examples. In addition, in the following Examples and Comparative Examples, the raw materials and the evaluation methods used for the evaluation are as follows. (1) Raw material a. Preparation of master chip 1 g of 12-amidododecanoic acid chloride aqueous solution with a concentration of 1 N per 100 g of montmorillonite having an average particle size of 1 μm
0 liter was mixed and stirred. Next, this was filtered, washed with water and dried to obtain a complex of montmorillonite and ammonium 12-aminododecanoate ion. In a closed reaction vessel equipped with a stirrer, 10 kg of ε-caprolactam and water 1
A predetermined amount of the complex was mixed so that the montmorillonite content in the resin composition was 4%, and the mixture was stirred at 80 ° C. until the reaction system became uniform. Next, set the reaction system to 2
The mixture was heated to 60 ° C. and stirred for about 1 hour while the pressure inside the reaction vessel was 1.5 MPa. Return the pressure to normal pressure and 260 ℃
The mixture was stirred for about 1 hour, and further stirred for about 1 hour while removing water in the reaction system under a nitrogen stream. When the polymerization was completed, the reaction product was dispensed into a water bath in a strand form, cooled, solidified, and cut to obtain pellets of a polyamide resin composition in which montmorillonite was uniformly dispersed. The pellets were treated in warm water at 95 ° C for about 6 hours to extract soluble components, and then dried under reduced pressure at 80 ° C. By the above method, a nylon 6 resin composition containing 4% of montmorillonite was obtained. The relative viscosity of the obtained resin composition was 2.7. b. Preparation of silica master chip 10 kg of ε-caprolactam, 1 kg of water, and 500 g of silica (manufactured by Fuji Silysia Chemical Ltd., trade name: Sylysia 310P) were placed in a closed reaction vessel equipped with a stirrer and kept at 100 ° C. The mixture was stirred at this temperature until the inside of the reaction system became uniform. Subsequently, the mixture was heated to 260 ° C. with stirring, the pressure was kept at 1.5 MPa for 1 hour, the pressure was released to normal pressure over 1 hour, and the polymerization was conducted for 1 hour. When the polymerization was completed, the reaction product was discharged in a strand form, cooled, solidified, and then cut to obtain a pellet made of a polyamide resin. The pellets are then placed at 95 ° C.
After the soluble component was extracted by treating the same in warm water for about 8 hours, it was dried under reduced pressure at a temperature of 80 ° C. The obtained polyamide resin had a relative viscosity of 2.7. (2) Evaluation method a. Relative viscosity of polyamide resin: 96 mass% Dry pellets of each resin were dissolved in concentrated sulfuric acid so that the concentration became 1 g / dl, and the temperature was measured at 25 ° C. b. Moisture absorption elongation (%) in TD direction: Stretched film 20
Humidity is maintained for 1 day in the atmosphere of 40 ° C and 40% RH, MD direction x T
A sample of D direction = 10 mm × 150 mm was prepared, and the length (A) of the initial sample in the TD direction was measured. 20 in succession
The humidity was changed in the atmosphere of 80 ° C. and 80% RH, the humidity was controlled for one day, and then the length (B) in the TD direction of the sample was measured. Using this measurement result, the hygroscopic elongation (C) in the TD direction was calculated by the following formula.

C (%) = {(B−A) / A} × 100 c. Hot water shrinkage (%): Stretched film at 20 ° C, 65%
The humidity was controlled for 1 day under the condition of RH, parallel lines with 100 mm intervals were marked with an oil-based ink, and this was slit into a width of 10 mm. Then, the dimension between the marks (dimension before treatment: P) was measured. Next, this sample was boiled in hot water at 100 ° C. for 5 minutes to remove the attached water, and then again subjected to 20 times.
After humidity conditioning for 1 day in an atmosphere of 65 ° C. and 65% RH, the dimension between marks (dimension after treatment: Q) was measured. The hot water shrinkage ratio (BS) was determined from the following formula using the measurement results.

BS (%) = {(P−Q) / P} × 100 d. Plane orientation coefficient: The refractive index in the main orientation direction (Nx) of the stretched film, its vertical direction (Ny), and the thickness direction (Nz),
It was measured using a digital refractometer RX-2000 manufactured by ATAGO Co., Ltd., and the surface orientation coefficient (X) was obtained from the following formula.

X = {(Nx + Ny) / 2} -Nz e. Puncture strength (N): The film is tensioned and fixed to a circular mold having an inner diameter of 100 mmφ, and a needle having a tip with a radius of curvature of 0.5 mm is vertically applied to the sample surface at a speed of 50 mm / min at the center of the sample. The strength at which the film was pierced and the film was broken was measured. f. Haze (%): measured using a haze meter manufactured by Tokyo Denshoku Co., Ltd. according to the method described in ASTM-D-1003. Example 1 As a main polyamide component, relative viscosity is 3.0, glass transition temperature Tg is 50 ° C., and crystallization peak temperature Tcp is 1.
Nylon 6 having a temperature of 20 ° C. and a melting point Tm of 225 ° C. was used. Then, each of the master chips prepared as described above was mixed such that 0.4% by mass of montmorillonite as a layered silicate and 0.2% by mass of silica as a lubricant were contained in this nylon 6, and the extrusion temperature was set to 260 to 270. The mixture was melt-kneaded at 0 ° C. and melt-extruded into a sheet form from a T die having a width of 630 mm. Then, by the air knife cast method, 20
The film was brought into close contact with a rotating drum at 0 ° C. and rapidly cooled to prepare a substantially amorphous and unoriented polyamide film.

Next, the unstretched film was sequentially biaxially stretched as follows. First, the unstretched film is introduced into a longitudinal stretching machine composed of a series of heating rollers having different peripheral speeds, and 5
The film was longitudinally stretched 2.8 times at a temperature of 5 ° C. to obtain a longitudinally stretched polyamide film.

Subsequently, this longitudinally stretched film was introduced into a tenter type horizontal stretching machine, gripped by clips, and preheated for stretching the film at 60 ° C. The film temperature Ti is 70 ° C. until the transverse stretching ratio reaches 2 times.
That is, higher than the glass transition temperature Tg of nylon 6 and the crystallization peak temperature Tcp of nylon 6
The temperature was adjusted so that the temperature was lower than that, and the stretching treatment was performed. When the transverse stretching ratio exceeded 2 times, the film temperature Ti was raised and the film was stretched until the stretching ratio reached 3.8 times, and the area ratio was set to 10.6. Then, the film temperature Te at this maximum draw ratio point is adjusted to be 180 ° C., that is, the temperature is higher than the melting point Tm-70 of nylon 6 and lower than the melting point Tm of nylon 6, and the successive stretching treatment is performed. went. After that, 160-220 ℃ in the same tenter
Constant width heat treatment and 4% relaxation heat treatment.

Both ends of the obtained biaxially stretched polyamide film were released from the clips, and the ears were trimmed and wound up to produce a film having a thickness of 15 μm. The obtained film (original) is 1000m with a slitter
It was slit into m width and wound up as a product.

From this film product, test pieces for measuring TD moisture absorption elongation (%), plane orientation coefficient, puncture strength (N), hot water shrinkage (%) and haze (%) were prepared. Table 1 shows the physical properties of the obtained test pieces.

[0047]

[Table 1] Example 2 The content of montmorillonite was set to 0.1% by mass. Then, a polyamide film was manufactured in the same manner as in Example 1 except for the above, and each test piece was manufactured.

Table 1 shows the physical properties of the obtained test pieces. Example 3 The content of montmorillonite was set to 1.0% by mass. Then, a polyamide film was manufactured in the same manner as in Example 1 except for the above, and each test piece was manufactured.

Table 1 shows the physical properties of the obtained test pieces. Example 4 The film temperature Te was set to 200 ° C. A polyamide film was produced in the same manner as in Example 1 except for the above, and each test piece was produced.

Table 1 shows the physical properties of the obtained test pieces. The polyamide films obtained in Examples 1 to 4 were obtained by melt-casting a resin composition in which a layered silicate was uniformly dispersed in a polyamide resin at a predetermined ratio, and successively biaxially produced under the conditions of the present invention. Since the film was stretched, a hygroscopic elongation in the TD direction was small even in a high humidity atmosphere, and a film excellent in printability and laminating processability was obtained. Further, a plane orientation coefficient of 0.05 or more was obtained, a puncture strength was as high as 10 N or more, and a film having a small hot water shrinkage rate was obtained. In addition, haze is 5
% Or less, and a film having excellent transparency was obtained. Such a polyamide film could be suitably used as a packaging material. Comparative Example 1 Montmorillonite was not added. Then, a polyamide film was produced in the same manner as in Example 1 except for the above, and each test piece was produced.

Table 1 shows the physical properties of the obtained test pieces. Comparative Example 2 The compounding ratio of montmorillonite was set to 0.05% by mass, which is less than the range of the present invention. And other than that, Example 1
A polyamide film was prepared in the same manner as in, and each test piece was prepared.

Table 1 shows the physical properties of the obtained test pieces. Comparative Example 3 The compounding ratio of montmorillonite was set to 2.0% by mass, which is higher than the range of the present invention. Then, a polyamide film was produced in the same manner as in Example 1 except for the above, and each test piece was produced.

Table 1 shows the physical properties of the obtained test pieces. Comparative Example 4 The film temperature Te was set to 90 ° C., which is lower than the range of the present invention. A polyamide film was produced in the same manner as in Example 1 except for the above, and each test piece was produced.

Table 1 shows the physical properties of the obtained test pieces. Comparative Example 5 The film temperature Ti was set to 140 ° C, which is higher than the range of the present invention. A polyamide film was produced in the same manner as in Example 1 except for the above, but film breakage occurred frequently and a test piece could not be produced. Comparative Example 6 The film temperature Te was set to 240 ° C., which is higher than the range of the present invention. A polyamide film was produced in the same manner as in Example 1 except for the above, and each test piece was produced.

Table 1 shows the physical properties of the obtained test pieces. Comparative Example 7 The stretching ratio was 2.4 times in the longitudinal direction and 3.2 times in the lateral direction, and the areal magnification was 7.68 times. A polyamide film was produced in the same manner as in Example 1 except for the above, and each test piece was produced.

Table 1 shows the physical properties of the obtained test pieces. In Comparative Examples 1 and 2, montmorillonite was not blended, or the blending ratio was too small, so that the hygroscopic elongation in the TD direction was large and the printability and the laminating processability were poor.

In Comparative Example 3, since the blending ratio of montmorillonite exceeded the range of the present invention, the hygroscopic elongation in the TD direction was small, but the haze was high, whitening occurred, the transparency was poor, and the appearance was poor. became.

In Comparative Example 4, since the film temperature Te was lower than the range of the present invention, voids were generated during stretching and haze was increased, resulting in poor appearance. In Comparative Example 5, since the film temperature Ti was set higher than the range of the present invention, crystallization preferentially proceeded in the initial stage of stretching, and the film was whitened and ruptured, so that the test film could not be prepared as described above. It was

In Comparative Example 6, the film temperature Te was set higher than the range of the present invention, so that the generated crystals were melted and the crystallinity was lowered, and as a result, only those having a large hygroscopic elongation were obtained.

Comparative Example 7 has a low draw ratio and an area ratio of 9
Since it was less than twice, the plane orientation coefficient of the film was low, the puncture strength was small, and the mechanical strength was poor. Example 5 Nylon 6 having a melting point of 225 ° C., a relative viscosity of 3.0, a glass transition temperature Tg of 50 ° C., a crystallization peak temperature Tcp of 120 ° C. and a melting point of 225 ° C. was used as a main polyamide component. Then, each of the master chips prepared as described above was mixed so that the nylon 6 contained 0.4% by mass of montmorillonite as a layered silicate and 0.15% by mass of silica as a lubricant, and the extrusion temperature was from 260 to 27.
The mixture was melt-kneaded at 0 ° C. and melt-extruded into a sheet form from a T die having a width of 630 mm. Then, by an air knife casting method, it was brought into close contact with a rotating drum at 20 ° C. and rapidly cooled to prepare a substantially amorphous and unoriented polyamide film.

Then, the unstretched film was subjected to the following simultaneous biaxial stretching. First, in order to match the unstretched film with the entrance width of the tenter simultaneous biaxial stretching machine described later, both ends are cut so that the width becomes 260 mm,
Guide it to a tenter type simultaneous biaxial stretching machine with the width between the tips of the inlet crib set to 210 mm, grip it with clips, and
Preheating for film stretching was performed at 0 ° C. The film temperature Ti of this film was set to 70 ° C. until the surface magnification reached 4 times, that is, higher than the glass transition temperature Tg of nylon 6 and lower than the crystallization peak temperature Tcp of nylon 6. The temperature was adjusted so that it was subjected to a stretching treatment. When the areal ratio exceeds 4 times, the film temperature Ti is increased so that the film temperature Te at the maximum draw ratio point at which the areal ratio becomes maximum is 180 ° C., that is, higher than the melting point Tm-70 of nylon 6, 6
The temperature was adjusted to be lower than the melting point Tm of, and stretched to 3.0 times in the longitudinal direction and 3.3 times in the transverse direction. Then, a constant width heat treatment at 160 to 215 ° C. and a relaxation heat treatment at 4% were performed in the same tenter.

The both ends of the obtained biaxially stretched polyamide film were released from the clips, and the ears were trimmed and wound up to prepare a film having a thickness of 15 μm. The obtained film (original) is 500 mm with a slitter.
It was slit into a width and rolled up as a product.

From this film product, test pieces for measuring TD moisture absorption elongation (%), plane orientation coefficient, puncture strength (N), hot water shrinkage (%) and haze (%) were prepared. Table 2 shows the physical properties of the obtained test pieces.

[0064]

[Table 2] Example 6 The content of montmorillonite was set to 0.1% by mass. Then, a polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

Table 2 shows the physical properties of the obtained test pieces. Example 7 The content of montmorillonite was set to 1.0% by mass. Then, a polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

The physical properties of the obtained test piece are shown in Table 2. Example 8 The film temperature Te was set to 200 ° C. A polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

Table 2 shows the physical properties of the obtained test pieces. The polyamide films obtained in Examples 5 to 8 were formed by melt-casting a resin composition in which a layered silicate was uniformly dispersed in a polyamide resin at a predetermined ratio, and simultaneously biaxially produced under the conditions of the present invention. Since the film was stretched, a hygroscopic elongation in the TD direction was small even in a high humidity atmosphere, and a film excellent in printability and laminating processability was obtained. Further, a plane orientation coefficient of 0.05 or more was obtained, a puncture strength was as high as 10 N or more, and a film having a small hot water shrinkage rate was obtained. In addition, haze is 5
% Or less, and a film having excellent transparency was obtained. Such a polyamide film could be suitably used as a packaging material. Comparative Example 8 Montmorillonite was not added. Then, a polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

The physical properties of the obtained test piece are shown in Table 2. Comparative Example 9 The compounding ratio of montmorillonite was set to 0.05% by mass, which is less than the range of the present invention. And other than that, Example 5
A polyamide film was prepared in the same manner as in, and each test piece was prepared.

The physical properties of the obtained test piece are shown in Table 2. Comparative Example 10 The compounding ratio of montmorillonite was set to 2.0% by mass, which is higher than the range of the present invention. Then, a polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

Table 2 shows the physical properties of the obtained test pieces. Comparative Example 11 The film temperature Te was set to 90 ° C., which is lower than the range of the present invention. A polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

Table 2 shows the physical properties of the obtained test pieces. Comparative Example 12 The film temperature Ti was set to 140 ° C, which is higher than the range of the present invention. A polyamide film was produced in the same manner as in Example 5 except for the above, but film breakage occurred frequently and a test piece could not be produced. Comparative Example 13 The film temperature Te was set to 230 ° C. higher than the range of the present invention. A polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

Table 2 shows the physical properties of the obtained test pieces. Comparative Example 14 Stretching ratio is 2.7 times in the longitudinal direction and 3.0 times in the lateral direction, and the areal ratio is 8.
It was set to 1 time. A polyamide film was produced in the same manner as in Example 5 except for the above, and each test piece was produced.

Table 2 shows the physical properties of the obtained test pieces. In Comparative Examples 8 and 9, since montmorillonite was not blended or the blending ratio was too small, the hygroscopic elongation in the TD direction was large and printability and laminating processability were poor.

In Comparative Example 10, since the blending ratio of montmorillonite exceeded the range of the present invention, the hygroscopic elongation in the TD direction was small, but the haze was high, whitening occurred, the transparency was poor, and the appearance was poor. became.

In Comparative Example 11, since the film temperature was set to Te lower than the range of the present invention, voids were generated during stretching and haze was increased, resulting in poor appearance. In Comparative Example 12, since the film temperature Ti was set higher than the range of the present invention, crystallization was preferentially promoted in the initial stage of stretching, and the film was whitened and ruptured, so that the test film could not be prepared as described above. It was

In Comparative Example 13, since the film temperature Te was set higher than the range of the present invention, melting of the produced crystals proceeded to lower the crystallinity, and as a result, only those having large hygroscopic elongation were obtained.

In Comparative Example 14, the stretching ratio was low and the surface magnification was less than 9 times, so that the surface orientation coefficient of the film was low, the puncture strength was small, and the mechanical strength was poor.

[0078]

According to the present invention, the polyamide resin 99.
Layer silicate 0.1 to 1.0% by mass in 9 to 99.0% by mass
Is a film composed of a resin composition in which are uniformly dispersed, at 20 ° C., 40% RH, and 20 ° C., 80% R
When the film has a hygroscopic elongation in the TD direction of 1.3% or less, a haze of 5.0% or less, and a plane orientation coefficient of 0.05 or more when the humidity is changed to an H atmosphere. In addition, even in a high-humidity atmosphere, a film having a small hygroscopic elongation and excellent printability and laminating processability can be obtained, and the application range of the successive biaxially stretched polyamide film which has been limited so far can be expanded. Therefore, such a polyamide film can be suitably used as a packaging material for foods, pharmaceuticals, miscellaneous goods, and the like.

Further, the polyamide film of the present invention has good operability and is stable by subjecting an unstretched film to sequential stretching or simultaneous biaxial stretching under a specific temperature condition using the resin composition having the above-mentioned mixing ratio. Can be manufactured.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 B29L 7:00 F term (reference) 4F071 AA35 AB26 AD05 AF10 AF14 AF30 AH04 BA01 BB06 BB07 BB08 BC01 4F210 AA29 AB16 AB27 AR06 QC06 QC07 QD16 QG01 QG18 4J002 CL001 CL011 CL031 CL051 CL062 DJ006 FA016

Claims (4)

[Claims] 1. A film comprising a resin composition in which 0.1-9% by mass of layered silicate is uniformly dispersed in 99.9-99.0% by mass of a polyamide resin, and the film is at 40 ° C. and 40 ° C.
The moisture absorption elongation in the TD direction is 1.3% or less, the haze is 5.0% or less, and the plane orientation coefficient is 0 when the humidity is changed from a% RH atmosphere to a temperature of 20 ° C. and a 80% RH atmosphere. A polyamide film having a thickness of 0.05 or more. 2. The polyamide film according to claim 1, wherein the polyamide resin contains an aliphatic polyamide as a main component. 3. A resin composition in which 0.1 to 1.0% by mass of layered silicate is uniformly dispersed in 99.9 to 99.0% by mass of polyamide resin is melt-cast and the unstretched film is longitudinally stretched. After stretching in the direction, the film temperature (Ti) is set in the range of Tg ≦ Ti ≦ Tcp until the transverse stretching ratio reaches 2 times, and the film temperature (Te) at the maximum stretching ratio point at which the transverse stretching ratio becomes maximum is A method for producing a polyamide film, which comprises laterally stretching in the range of Tm-70 ≦ Te ≦ Tm, and forming a film by this sequential biaxial stretching. Tg: glass transition temperature of polyamide resin Tcp: crystallization peak temperature of polyamide resin Tm: melting point of polyamide resin 4. A resin composition, in which 0.1 to 1.0% by mass of layered silicate is uniformly dispersed in 99.9 to 99.0% by mass of polyamide resin, is melt-cast and the unstretched film is Film temperature (Ti) Tg ≦
The film temperature (Te) at the maximum draw ratio point at which the areal ratio is maximized is Tm−70 ≦ Te ≦, where Ti ≦ Tcp.
A method for producing a polyamide film, comprising simultaneously biaxially stretching as a range of Tm to form a film. Tg: glass transition temperature of polyamide resin Tcp: crystallization peak temperature of polyamide resin Tm: melting point of polyamide resin