JPH0146303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a highly efficient method for producing a polyamide film with excellent thickness uniformity. <Purpose of the invention> Polyamide film has strong toughness,
It is widely used in the field of food packaging where it can take advantage of properties such as impact resistance, pinhole resistance, and oxygen barrier properties. In recent years, with the growth of retort food products, the demand for polyamide films has also increased, and there is a desire to supply high-quality and inexpensive films. <Relationship with Prior Art> Polyamide films are usually produced by melt extrusion using an inflation method or a T-die method. When obtaining a polyamide film by the T-die method, the molten film extruded from the die is cast onto a rotating cooling roll. At this time, in order to bring the film into close contact with the cooling rotating roll, there is a method of blowing air with an air knife (hereinafter referred to as the "air knife method"), a method of depositing a charge on the molten film from a high-voltage electrode and making it adhere electrostatically (hereinafter referred to as the "electrostatic" method). (referred to as the close contact method).
However, even in casting using the air knife method or electrostatic adhesion method, when the take-up speed increases, air is caught between the rotating cooling roll and the film due to the flow generated by the rotation, making it difficult to form a uniform film. You won't be able to get it. In order to efficiently produce a polyamide film with excellent thickness uniformity, the inventors of the present invention conducted extensive research and found that they copolymerized an aromatic residue with an aliphatic polyamide resin and added a metal compound to the aliphatic polyamide resin. The inventors have discovered that the electrostatic adhesion of the resin is improved by containing it, and have arrived at the present invention. <Structure of the invention> That is, the present invention provides aromatic aminocarboxylic acid residues,
2% to 20% by weight of aromatic dicarboxylic acid residues and/or aromatic diamine residues, and 80% by weight of aliphatic aminocarboxylic acid residues, aliphatic dicarboxylic acid residues, and/or aliphatic diamine residues % or more and 98% by weight or less, which also contains a metal compound and has a specific melt resistance of 1.5 x 10 ⁵ Ωcm or less at 260°C, is melt-extruded into a film, and the melt-extruded This method produces a polyamide film by electrostatically adhering the film to a rotating cooling roll and cooling and solidifying it. The present invention will be explained in more detail below. In the present invention, aromatic aminocarboxylic acid residues, aromatic dicarboxylic acid residues, and/or aromatic diamine residues include aminomethylbenzoic acid, terephthalic acid, isophthalic acid, 2,4-bis(carboxymethyl)
These are residues such as toluene, paraxylylene diamine, metaxylylene diamine, and 2,4-bis(aminomethyl)toluene. On the other hand, aliphatic aminocarboxylic acid residues, aliphatic dicarboxylic acid residues, and/or aliphatic diamine residues include epsilon caprolactam, omega laurolactam, aminocaproic acid, aminoundecanoic acid, aminododecanoic acid, adipic acid, and sebacic acid. , alpha omega dodecanoic acid, hexamethylene diamine, etc. The aromatic residue in the polymer is preferably 2% by weight or more and 20% by weight or less.
If it is less than 2% by weight, the effect of improving the electrostatic adhesion of the molten resin will be small, and if it is more than 20% by weight, the pellets will fuse and become difficult to handle, or conversely, the melting point of the resin will become high, making molding difficult. The polyamide resin containing these aromatic residues in the copolymer can also be used in combination with other polyamide resins. These resins may contain small amounts of other resins, lubricants, antioxidants, antistatic agents, colorants, and other organic or inorganic substances. The metal compounds in the present invention include alkali metals, alkaline earth metals, aluminum group elements,
There are transition metal halides, sulfur oxygen acid compounds, phosphorus oxygen acid compounds, hydroxides, organic carboxylates, organic sulfonates, etc. Specifically, sodium chloride, lithium chloride, potassium chloride, magnesium chloride. , calcium chloride, aluminum chloride, zinc chloride, copper chloride, cobalt chloride,
Sodium bromide, lithium bromide, magnesium bromide, potassium iodide, sodium iodide, sodium sulfate, magnesium sulfate, zinc sulfate, sodium phosphate, potassium phosphate, sodium phosphite,
Sodium hypophosphite, calcium hypophosphite,
Sodium hydroxide, lithium hydroxide, sodium stearate, potassium stearate, magnesium stearate, calcium stearate, aluminum stearate, zinc stearate, potassium oleate, sodium acetate, potassium acetate, sodium benzoate, sodium lauryl sulfonate, Examples include sodium benzenesulfonate. In addition, a metal base-containing compound capable of forming an amide bond, such as 5-sodium sulfoisophthalic acid, may be added to bond the metal base directly to the polyamide chain. The present invention is not limited to the above-mentioned metal compounds, as long as the polyamide contains a metal compound and has a specific melting resistance of 1.5×10 ⁵ Ωcm or less at 260° C. In addition, in the case of metals with small ionization potential such as alkali metals and alkaline earth metals,
It is also possible to use it alone. By containing these metal compounds in an amount of 0.0005% to 5% by weight based on the polyamide resin, it is possible to reduce the specific melting resistance at 260° C. to 1.5×10 ⁵ Ωcm or less. When the metal compound content is 0.0005% by weight or less, the effect of improving electrostatic adhesion is small. If the metal compound content is 5% by weight or more, the physical properties of the film will deteriorate, which is not preferable. However, the present invention is not limited to these metal compound content ranges. Methods for adding a metal compound include adding it to the raw material monomer before polymerization, adding it during the progress of polymerization, adding it during the extraction process, adding it when drying the pellets,
Either is fine. It is effective if the metal compound is finally contained in the melt-extruded polyamide resin, and the present invention is not limited to these methods of addition. In the present invention, as a method for electrostatically bringing the roller into close contact with the rotating cooling roll, a high voltage is applied to a wire electrode, a knife-shaped electrode, and/or a deep needle-shaped electrode as disclosed in, for example, Japanese Patent Publication No. 37-6142. A method of imparting charge to the film can be applied. However, the present invention is not limited only to this method, but can also be applied to an electrostatic adhesion device that uses an air knife in combination, and by coating a rotating cooling roll with a dielectric material and applying an electric charge of the opposite sign to that of a high-voltage charged electrode. It is also possible to apply it to a device that deposits on a rotating cooling roll. In the case of the method of the present invention, the electrostatic adhesion of the molten resin to the rotating cooling roll in these devices is improved compared to the case of using ordinary polyamide resin. <Effects of the Invention> The take-up speed of the unstretched film in the method of the present invention is not particularly limited. If the take-up speed is increased, air will be caught between the rotating cooling roll and the molten film, making it impossible to obtain a uniform unstretched film. When many conventional polyamide resins are transferred to a rotating cooling roll using the electrostatic adhesion method,
While the maximum take-up speed is normally 10 to 35 m/min, the present invention prevents air from being trapped between the rotating cooling roll and the molten film even at this take-up speed or higher, and produces a film with a uniform thickness. A stretched film is obtained. The unstretched polyamide as it is is suitable for packaging foods and the like. However, the unstretched polyamide film is further expanded by 1.1 times or more in at least one direction, preferably by 2.0 times or more in each of two orthogonal directions.
A biaxially stretched film stretched 5.0 times has further improved mechanical strength, transparency, and oxygen barrier properties, and is suitable for various packaging films. <Examples> The present invention will be explained in more detail below by showing examples. In addition, the melt specific resistance of the resin in the present invention is 260
A stainless steel electrode was inserted into the molten resin kept at ℃, and a DC voltage of 100V was applied, causing
From the current value after 5 seconds, specific resistance ρ = (S/L)
This is a value calculated from the formula ×(V/I). Here, ρ is specific resistance (Ωcm), S is electrode area (cm ² ), L is distance between electrodes (cm), V is voltage (V), and I is current (A). In the measurement in this example, S is 0.12cm ² and L is
It was 1.5cm. In addition, the relative viscosity of the resin in the Examples is a value measured by dissolving the resin in 96.3 concentrated sulfuric acid at a concentration of 1.0/100ml and using an Ostwald viscometer in a constant temperature bath at 20°C. Example 1 For 100 parts by weight of epsilon caprolactam,
A nylon salt aqueous solution prepared by dissolving 6.9 parts of meta-xylene diamine and 7.4 parts of adipic acid in 14.3 parts by weight of hot water was added, and after polycondensation under pressure at 180 to 240°C, further
Atmospheric polycondensation was carried out at 240 to 270°C to obtain copolyamide resin pellets with a relative viscosity of 2.6. After the pellets were subjected to a treatment to extract residual laxem with hot water, 0.05 parts by weight of trisodium phosphate dodecahydrate was added to 100 parts by weight of the pellets, dried in a rotary vacuum dryer, and the mixed pellets were used. The maximum take-up speed was determined to be 59 m/min, which was sufficient to prevent air from getting caught between the rotating cooling roll and the molten film. Example 2 For 100 parts by weight of epsilon caprolactam,
Meta-xylene diamine 13.8 parts by weight, adipic acid
An aqueous solution of nylon salt in which 14.8 parts by weight was dissolved in 28.6 parts by weight of hot water was added, followed by pressure polycondensation at 180 to 240°C, followed by normal pressure polycondensation at 240 to 270°C. Copolymerized polyamide resin pellets with a relative viscosity of 2.6 were obtained. After extracting the remaining lactam from the pellets with hot water, parts by weight of trisodium phosphate dodecahydrate were added to 100 parts by weight of the pellets, and the pellets were dried and mixed in a rotary vacuum dryer. When the maximum take-up speed was determined using this method, it was possible to prevent air from getting caught between the rotating cooling roll and the molten film up to 62 m/min. Example 3 100 parts by weight of epsilon caprolactam, metaxylylene diamine and nylon salt of isophthalic acid
11.5 parts by weight and 1.5 parts by weight of water were subjected to pressure polycondensation at 180 to 240°C, followed by normal pressure polycondensation at 240 to 270°C to obtain copolymerized polyamide resin pellets with a relative viscosity of 2.6. After extracting the residual lactam from the pellets with hot water, 0.05 parts by weight of trisodium phosphate dodecahydrate was added to 100 parts by weight of the pellets.
The maximum take-up speed was determined using pellets dried and mixed in a rotary vacuum dryer and was 60 m/min.
It was possible to prevent air from getting caught between the rotating cooling roll and the molten film for up to a minute. Comparative example 1 100 parts by weight of epsilon caprolactam and water
After polycondensing 1.5 parts by weight at 180 to 240℃ under pressure, further polycondensation at normal pressure at 240 to 270℃ resulted in a relative viscosity of 2.6.
Polycaprolactam resin pellets were obtained. After extracting the residual lactam using hot water, the pellets were dried in a rotary vacuum dryer, and the maximum take-up speed was determined using the pellets.
At m/min, air was caught between the rotating cooling roll and the molten film, causing uneven thickness and opaque areas in the film. Comparative Example 2 To 100 parts by weight of polycapramide resin pellets obtained in the same manner as in Comparative Example 1 after the residual lactam extraction treatment, 0.05 parts by weight of trisodium phosphate decahydrate was added, and the mixture was dried in a rotary vacuum dryer. When the maximum take-up speed was determined using the dried and mixed pellets, air was caught between the rotating cooling roll and the molten film at a speed of 56 m/min, resulting in uneven thickness and opaque areas in the film. 【table】

Claims (1)

[Claims] 1 Aromatic aminocarboxylic acid residues, aromatic dicarboxylic acid residues, and/or aromatic diamine residues of 2% to 20% by weight, and aliphatic aminocarboxylic acid residues, aliphatic dicarboxylic acid residues, and/or Aliphatic diamine residues are 80% by weight or more and 98% by weight
A polyamide resin consisting of the following, containing a metal compound, and having a specific melting resistance of 1.5× at 260℃
A method for producing a polyamide film, which comprises melt-extruding a polyamide resin having a resistance of 10 ⁵ Ωcm or less into a film, electrostatically adhering the melt-extruded film to a rotating cooling roll, and solidifying it by cooling.