JPH0280226A - Manufacture of antistatic polyamide biaxially oriented film - Google Patents

Abstract

PURPOSE:To obtain antistatic effect sufficient for practical use with the small quantity of an antistatic agent by water absorbingly treating a non-oriented film manufactured by means of melt extruded polyamide resin including a water soluble antistatic agent in a manner that water absorption rate is in the given range before biaxial orientation of the film and heat treating after orientation. CONSTITUTION:As for suitable polyamide, poly-caprolactam (nylon 6) and polyhexamethylene adipamide (nylon 66) can be used. A water soluble antistatic agent is an antistatic agent of a surface active properties when dissolved in water, and as a suitable antistatic agent, alkyl sulfonic acid sodium salt, alkyl benzene sulfonic acid sodium salt or the like can be used. The adding quantity of the antistatic agent is 0.05wt.%-3wt.%, preferably 0.1wt.%-2wt.%. The water absorption treatment of manufactured non-oriented film should be carried out at 70 deg.C or lower. Water absorption rate is 1-8wt.%, preferably 3-6wt.%. Water absorption treated non-oriented film is biaxially oriented successively or simultaneously. The orientation temperature is almost similar to the orientation temperature of an ordinary polyamide film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a polyamide film. Specifically, the present invention relates to a method for producing a polyamide film with improved antistatic properties.

(Conventional technology) Mechanical properties of biaxially stretched polyamide films.

Not to mention optical properties, thermal properties, and barrier properties.

It is widely used mainly in the food packaging field due to its excellent abrasion resistance, impact resistance, and pinhole resistance.

However, since the polyamide resin itself has a high degree of electrical insulation, polyamide films are extremely easily charged, causing various problems due to the generation and accumulation of static electricity.

Conventionally, methods of adding antistatic agents to polyamide films have been studied in order to improve the above-mentioned drawbacks.

(Problem to be Solved by the Invention) However, in the method of simply adding an antistatic agent as described above, it is difficult to make the concentration of the antistatic agent present in the necessary amount on the film surface necessary for substantially preventing static electricity. However, a considerable amount must be present inside the film, which impairs the mechanical properties and transparency of the film and increases the cost, which is economically disadvantageous.

(Means for Solving the Problems) In order to improve these problems, the inventors of the present invention, as a result of intensive studies, subjected a polyamide sheet to which a water-soluble antistatic agent was added to water absorption treatment before stretching it.

When a stretched film was then produced by stretching and heat treatment, it was discovered that a practically sufficient antistatic effect could be obtained even with a small amount of antistatic agent, and the present invention was achieved based on this finding.

That is, the present invention provides a method for producing a polyamide biaxially stretched film in which an unstretched film obtained by melt-extruding a polyamide resin containing a water-soluble antistatic agent is then biaxially stretched, in which the unstretched film is adjusted to have a water absorption rate before stretching. 1~8w
This is a method for producing an antistatic polyamide biaxially stretched film, which is characterized in that it is subjected to a water absorption treatment so that the film becomes t%, and is then subjected to a heat treatment after stretching.

Next, the present invention will be explained in detail.

The polyamide according to the present invention is a linear polymer compound having an amide bond -CONH- in its molecule, such as polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacate, etc. Mido (nylon 610), polyaminoundecanoic acid (nylon 11), polylaurinraccum (nylon 12)
and copolymers thereof. One particularly suitable polyamide for the present invention is polycaprolactam (nylon 6) and polyhexamethylene adipamide (nylon 66).

Furthermore, the water-soluble antistatic agent of the present invention is an antistatic agent that exhibits surface activity when dissolved in water.

Sulfonic acid base, sulfate ester base as hydrophilic group.

Anionic antistatic agent having a phosphate ester base, a phosphonate base, a quaternary ammonium base as a hydrophilic group,
A cationic antistatic agent having a pyridinium base and a polyethylene polyamine group, and an aminoalcohol group and a glycerin group as hydrophilic groups.

Examples include nonionic antistatic agents having a sorbitol group, polyhydric alcohol group, or polyethylene glycol group, and amphoteric antistatic agents having an amino acid group, betaine group, sulfobetaine group, or aminosulfate group as a hydrophilic group.

Particularly suitable antistatic agents for the present invention include alkyl sulfonic acid sodium salts, alkylbenzene sulfonic acid sodium salts, polyoxyethylene alkyl ether phosphates, benzalkonium chloride, distearyl dimethyl ammonium chloride, polyethylene glycol, polyoxy Ethylene alkylphenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl ether.

Examples include polyoxyethylene alkyl phenyl ether polyglycerin fatty acid ester and cocoamidopropyl betaine.

The amount of the antistatic agent of the present invention added is 0.05wt% to 3
wt%, preferably 0.1 wt% to 2 wt%.

If the amount added is less than 0.05 wt%, a sufficient antistatic effect cannot be obtained even if produced by the method of the present invention, and if it is more than 3 wt%, the transparency and mechanical properties of the resulting film may be impaired. characteristics are impaired.

There are no particular limitations on the method of adding the antistatic agent to the polyamide resin, but methods include adding the antistatic agent during polymerization of the polyamide resin, blending and melt-mixing the polyamide resin and the antistatic agent, and adding the antistatic agent to the polyamide resin. There is a method of adding an antistatic agent immediately before resin film formation. The thus obtained polyamide resin containing an antistatic agent can be produced by a conventional polyamide film forming method 1, for example, the T-die method.

Films can be formed by the inflation method, etc.

In the present invention, the unstretched film thus obtained needs to be subjected to water absorption treatment before being subjected to stretching.

As a method for this, methods such as immersing the unstretched film in water or exposing it to a high temperature atmosphere can be used. The water temperature and treatment time in this treatment may be appropriately selected depending on the water absorption rate, but the water temperature
Must be below 0'C. If this temperature exceeds 70°C, crystallization of the unstretched film will proceed during the water absorption treatment, and breakage will likely occur in the stretching step after the treatment. In addition, the water absorption rate is 1 to 8 wt%, preferably 3 to 6 wt%.
It is wt%. If the water absorption rate is less than 1 wt%, a sufficient antistatic effect cannot be obtained, and if it exceeds 8 wt%, the stretchability after water absorption becomes poor.

The unstretched film treated with water absorption in this manner is sequentially or simultaneously biaxially stretched. The stretching temperature can be approximately the same as that for ordinary polyamide films, but may be changed as necessary.

In addition, the stretching ratio is 1.
It can be carried out in a range of 2 to 6 times. The thus stretched film must be heat treated.

In the present invention, the meaning of heat treating the film after stretching is 5.
In addition to imparting antistatic properties, which is the object of the present invention, it is also the purpose of imparting thermal dimensional stability through crystallization.

Therefore, the antistatic properties of the present invention cannot be achieved unless the film is heat-treated.

Regarding the conditions for the heat treatment of the present invention, first, regarding the temperature and time of the heat treatment, for the purpose of imparting antistatic properties, it is necessary to set the temperature and time of the heat treatment to approximately the same amount of water as that taken into the polyamide film during the water absorption treatment. Although there are no particular limitations as long as the temperature and time are such that it can remove the This can be sufficiently achieved under the usual conditions of heat treatment for 1 to 60 seconds at a temperature of 150° C. or higher and lower than the melting point of the polyamide.

Next, a method for measuring characteristic values in the present invention will be explained.

(1) Electrostatic voltage half-life J l5-L-1094 method A, 20°C140
It is expressed as the half-life value of the charging voltage at %RH. The applied voltage was 10 V to 10 V, and the test was performed from a distance of 15 mm above the sample.

(2) Frictional charging voltage JIS-L-1094 method B, 20°C540%
l? In H, measurements were made using cotton cloth as a Y-shape.

(3) Transparency (haze value) Measured by JIS-6714 method.

(Function) According to the present invention, an unstretched film made of a polyamide resin to which a water-soluble antistatic agent has been added is subjected to water absorption treatment to a specific amount before being biaxially stretched, and then stretched and heat treated after stretching. By adding a small amount of antistatic agent,
An antistatic effect can be imparted to the polyamide film.

I do not know the details of this principle, but the water-soluble antistatic agent dissolves in the water incorporated into the polyamide, and as the water migrates to the surface of the film by heat treatment, the antistatic agent also migrates to the surface. Therefore, compared to manufacturing by simply adding an antistatic agent, the amount of antistatic agent transferred to the surface is substantially larger, and as a result, excellent antistatic properties can be achieved even with a relatively small amount of antistatic agent added. It is thought that it will be possible to grant the following.

(Example) Comparative Example 1 Polycaprolactam with a relative viscosity of 3.0 measured at 25°C in 96% concentrated sulfuric acid was melt-extruded from a T-die at 270°C, cooled on a drum at 30″C, and extruded to 173 μm. An unstretched film was obtained.Subsequently, this film was stretched 3 times in the longitudinal direction.
．． Simultaneously biaxially stretched 3 times and 3.5 times in the transverse direction at 80°C, and then heat-treated at 200°C for 5 seconds to obtain a 15 μm film.
A biaxially stretched film was obtained.

Comparative Example 2 99-t% of polycaprolactam of Comparative Example 1 and 1 wt% of alkylbenzenesulfonic acid sodium salt of I of Table 1
were mixed and melt-kneaded using an extruder set at 250°C to form pellets.

Next, from this pellet, according to the method of Comparative Example 1, 15 μm
A biaxially stretched film was obtained.

Table 1 Antistatic Agent Comparative Example 3 99.8 wt% of polycaprolactam of Comparative Example 1 and 0.2 wt% of alkylbenzenesulfonic acid sodium salt of Table 1
%, a 15 μm biaxially stretched film was obtained according to the method of Comparative Example 2.

Example 1 99.8wt% of polycaprolactam of Comparative Example 1 and 0.2% of alkylbenzenesulfonic acid sodium salt of ■ in Table 1
wt% were mixed and melt-kneaded using an extruder set at 250°C to form pellets.

The pellets were then melt-extruded through a 270''C''7'T die and cooled on a drum at 30''C to a diameter of 173μm.
An unstretched film was obtained. Next, rotate this film at 35°
It was immersed in water of C for 4 minutes and treated to absorb water to a water absorption rate of 4 wt%. After that, it is 3.3 times vertically and 3.5 times horizontally.

Stretched at 80°C and further heat treated at 200°C for 5 seconds.

A biaxially stretched film of 15 μm was obtained.

Comparative Example 4 A 15 μm biaxially stretched film was obtained in the same manner as in Example 1 except that the water absorption rate in the water absorption treatment was 0.5 ivt%.

Comparative Example 5 A 15 μm biaxially stretched film was obtained in the same manner as in Example 1 except that no heat treatment was performed after stretching.

Example 2 Using 99.8 wt% of polycaprolactam of Comparative Example 1 and 0.2 wt% of sorbitan fatty acid ester of ■ in Table 1,
A 15 μm biaxially stretched film was obtained according to the method of Example 1.

Comparative Example 6 Polycaprolactam 99wt% of Comparative Example 1 and ■ in Table 1
A 15 μm biaxially stretched film was obtained according to the method of Comparative Example 2 using 1 wt % of sorbitan fatty acid ester.

Comparative Example 7 Using 99.8 wt% of polycaprolactam of Comparative Example 1 and 0.2 wt% of sorbitan fatty acid ester of ■ in Table 1,
A 15 μm biaxially stretched film was obtained according to the method of Comparative Example 2.

Example 3 Using 99.8 wt% of the polycaprolactam of Comparative Example 1 and 0.2 imt% of Chemistuft 3033 (manufactured by Sanyo Chemical Co., Ltd.) of ■ in Table 1, which is a commercially available water-soluble antistatic g+1, A 15 μm biaxially stretched film was obtained according to the method.

Comparative Example 8 99.8 wt% polycaprolactam of Comparative Example 1 and Chemstand 3 of ■ in Table 1, which is a commercially available water-soluble antistatic agent.
A 15 μm biaxially stretched film was obtained according to the method of Comparative Example 2 using 0.2 wt% of 033 (manufactured by Sanyo Kasei Co., Ltd.).

Example 4 Polycaprolactam 99 of Comparative Example 1. ! A 15 μm biaxially stretched film was prepared according to the method of Example 1 using 0.1 wt % of Plysurf A212 C (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) shown in ■ in Table 1, which is a commercially available water-soluble antistatic agent. I got it.

Comparative Example 9 99.9 wt% polycaprolactam of Comparative Example 1 and Plysurf A of ■ in Table 1, which is a commercially available water-soluble antistatic agent.
A 15 μm biaxially stretched film was obtained according to the method of Comparative Example 2 using 0.1 wt% of 212C (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

The above results are shown in Table 2.

Table 2 As is clear from this table, only the film prepared by the method of the present invention exhibits excellent antistatic properties even with a small amount of antistatic agent added, and also has excellent transparency.

(Effects of the Invention) According to the present invention, an unstretched film obtained by adding an antistatic agent to a polyamide resin and melt-extruding the film is subjected to water absorption treatment to a specific water absorption amount before biaxial stretching.

In addition, by simply heat-treating the stretched film under the heat treatment conditions used to obtain thermal dimensional stability during the production of ordinary polyamide films, a polyamide film with excellent antistatic properties can be produced with a small amount of antistatic agent added. It becomes possible to do so.

Moreover, since the film thus obtained contains less antistatic agent, it has excellent transparency, and an antistatic polyamide film can be produced economically.

It has great industrial value.

Patent applicant: Unitika Co., Ltd.

Claims (1)

[Claims] (1) In a method for producing a biaxially stretched polyamide film, in which an unstretched film obtained by melt-extruding a polyamide resin containing a water-soluble antistatic agent is then biaxially stretched, the unstretched film has a water absorption rate of 1 before stretching. A method for producing an antistatic polyamide biaxially stretched film, which comprises subjecting it to water absorption treatment to a concentration of ~8wt%, and heat treatment after stretching.