JPS6227130A - Manufacture of polyamide film - Google Patents

Abstract

PURPOSE:To manufacture a polyamide film at high speed and efficiently without deteriorating uniformity in thickness and transparency, by a method wherein a metallic compound is contained in polcoupleamide resin whose methanol extractable content is less than 1.5wt%, and a specific quantity of polyamide resin whose fusion specific resistance is less than a specific level is compounded to the same. CONSTITUTION:A composite obtained by containing a metallic compound to 100wt part polycoupleamide series resin whose methanol extractable content is less than 1.5wt% and by compounding 0.01-30wt part polyamide resin whose fusion specific resistance is less than 1.0X10<5>cm at 260 deg.C to the same is melted and extruded into a filmlike state to adhere to a rotary cooling roll electrostatically, and a film is obtained by taking off the same while being quenched and cured. When said unoriented polyamide film is oriented at least more than 1.1 times unidirectionally further, mechanical strength, transparency and oxygen barrier properties are improved further. As for the polyamide resin, nylon 6 or nylon 66 can be mentioned and when the metallic compound is added, the fusion specific resistance can be lowered. As for the metallic compound, an alkaline metal or alkaline earth metal can be mentioned.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a highly efficient method for producing a polyamide film with excellent thickness uniformity.

(Prior art) Polyamide films, especially polycapramide films obtained by ring-opening polymerization of ε~caprolactam, are widely used in the field of food packaging due to their toughness, impact resistance, pinhole resistance, and high oxygen barrier properties. has been done. In recent years, the demand for polyamide films has been increasing as retort foods have become more popular, and there is a desire to supply high quality and inexpensive films.

Conventionally, polyamide films have been produced by a melt extrusion method using an injection method or a T-die method.

When obtaining a polyamide film by the T-die method, a molten film extruded from a gouer is cast onto a rotating cooling roll. At this time, in order to densely pack the film onto the cooling roll, there is a method of blowing air with an air knife (hereinafter referred to as the air knife method), a method in which charges are deposited on the molten film from a high-voltage electrode and the film is packed electrostatically (hereinafter referred to as the air knife method). static fI
(referred to as the t￥M-gyo method), etc. However, even in casting using the air knife method or the static mma method, when the take-up speed increases, air is caught between the rotating cooling roll and the film due to the accompanying air flow generated by the rotation, making it difficult to obtain a uniform film. It disappears.

The electrostatic ejaculation method involves inserting, for example, a wire-like electrode between a goo and a cooling roll to impart an electrostatic charge to a film-like object.
This method is disclosed in Japanese Patent Publication No. 37-6142, for example, for improving the uniformity and transparency of a formed film by electrostatically bringing the film material into close contact with a cooling roll. According to this method, the melt-extruded film material is strongly attracted to the cooling roll due to static electricity and is rapidly cooled, so that a thermoplastic resin film can be efficiently produced. Furthermore, in the case of polyamide resin, there is a method for cooling a polyamide thermoplastic polymer film, which is characterized by performing corona discharge in a streamer corona discharge state to precipitate charges on the molten film, and then electrostatically bringing the film close to a rotating cooling roll. has been disclosed (Japanese Unexamined Patent Publication No. 55-1
Publication No. 7559).

However, when manufacturing a polycapramide film, even if the electrostatic compaction method is used, the metal compound increases the production efficiency, and if the rotation speed of the cooling roll is increased, the compaction force becomes insufficient.1. Air is partially trapped between the film and the rotating cooling roll. In such areas, heat transfer between the cooling roll and the film deteriorates, resulting in uneven cooling between the fully adhered areas and the incompletely adhered areas, which significantly affects the uniformity and transparency of the product sheet. As a result, the value of the product is lost. Moreover, if the film is subsequently stretched in the 1- or 2-fold direction, there is a possibility that the film will break during the stretching process, making it impossible to form the film itself.

(Problems to be Solved by the Invention) The present invention provides a technique that overcomes the drawbacks of the prior art and can efficiently produce polyamide films at high speed without impairing the uniformity and transparency. is intended to provide i.

(Means for solving the problem) That is, the present invention has a methanol extractable substance content of 1.5% in total.
Contains a metal compound and has a specific melting resistance of 1.0% at 260°C, based on 100 parts by weight of the following polycapramide resin. Oxio' Qrs or less polyamide resin 0.01~30T! A polyamide film characterized in that a composition containing f parts is melt-extruded into a film, the melt-extruded film is electrostatically brought into close contact with a rotating cooling roll, and then taken off while being rapidly cooled and solidified to obtain a film. The present invention relates to a manufacturing method and a method of AHing a stretched polycapramide film by further stretching the film by a factor of 1.1 times or more in at least one direction. According to the present invention, a polyamide film with excellent uniformity and transparency can be efficiently produced.

Immediately after polymerization, polycapramide-based polymers contain large amounts of oligomers and caprolactam, and a method has been disclosed in which the impurities are removed by water extraction or the like, followed by drying and feeding into an extruder. (For example, U.S. Pat.
45964) However, the impurities remain in the polycapramide-based m-merite that has just been subjected to the normal water extraction process, and when further methanol extraction is performed, 1.5 fflff
More than i% of methanol extractables are obtained.

The present inventors have discovered that by using a polycapramide-based polymer whose methanol-extractable substance content has been reduced to 1.5fffffi% or less through special treatment as a raw material resin, the material is melt-extruded using a T-die and wound onto a cooling roll using an electrostatic adhesion method. The voltage that can be applied to the electrode can be increased when
It has been found that unstretched and stretched polyamide films with excellent uniformity and transparency can be obtained even when wound around a cooling roll at a higher speed, and the present invention was previously proposed.

According to the present invention, the methanol extractable content is 1.5 fr.
tm% or less of polycapramide resin, which contains a metal compound and has a melting specific resistance at 280'C of 1.
By blending a specific amount of polyamide resin of 0xlO'Qc* or less, it is possible to lower the melting resistivity of the entire composition and to suppress the methanol extractable content to a small amount, significantly improving electrostatic adhesion and achieving higher speeds. Even if the film is wound up on a cooling roll, unstretched and stretched polyamide films with excellent uniformity and transparency can be obtained.

The polycapramide resin used in the present invention is 70% by weight.
Examples include homopolymers, copolymers, and/or mixtures of polycapramide, each of which is composed of capramide units.

Examples of copolymers include hexamethylene diamine, metaxylylene diamine, amine dodecanoic acid, aminoundecanoic acid, adipic acid, sebacyl/Wt, in7-thalic acid, terephthalic acid, laurolactam, etc. with ε-caprolactam and/or amine-7 Examples include copolymers with cabroic acid.

Examples of mixtures include mixtures with other polyamide resins, such as polyhexamethylene adipamide, polymethaxylylene adipamide, etc., and mixtures with other polyolefin-based or polyester-based resins. Further, inorganic particles such as titanium oxide, silicon oxide, magnesium silicate, etc. may be included. In addition, it may contain an antistatic agent, a stabilizer, an antigelation agent, a slip agent, a light stabilizer, a coloring agent, and the like.

The methanol extractable content of these polyamide resins must be 1.5% by weight or less. More preferably, it is 0.9ff1% or less.

These polycapramide resins with a low content of methanol extractable substances can be obtained by washing polymer chips or pellets obtained by the usual continuous or /ichim method with a solvent that has a strong affinity for oligomers such as alcohol, and then washing the chips with hot water. The amount can be obtained by extracting the amount in two or more stages. Additionally, during polymerization or before chipping, the oligomer and caprolactam are removed from the system by passing the molten polymer under reduced pressure or an inert gas atmosphere, and the resulting polymer is further extracted with hot water or/and It is obtained by extraction with a solvent such as alcohol that has a strong affinity with oligomers. However, the present invention is not limited to these methods.

On the other hand, it contains the metal compound according to the present invention, and
Examples of the polyamide resin constituting the polyamide resin having a melting specific resistance at °C of i, oxtoゝΩ (minimum) or less include Relaylon 6, nylon 66, polyhexamethylene terephthalamide, polymethaxylylene/adipamide, and the like. When the polyamide resin does not contain a metal compound, the melting specific resistance at 260°C is usually L-0XIO1l.
The value may be greater than Qcs, but is not limited to this. When a metal compound is added to the polyamide resin, the specific melt resistance can be lowered. Examples of metal compounds to be blended into the polyamide resin in the present invention include alkali metals, alkaline earth metals, aluminum group elements, transition metal oxides, sulfur oxygen acid compounds, phosphorous oxygen acid compounds, and hydroxides. , organic carboxylates, organic sulfonates, and the like. Specifically, sodium chloride, lithium chloride, potassium chloride, magnesium chloride, calcium chloride,
aluminum chloride, zinc chloride, copper chloride, cobalt chloride,
Sodium bromide, potassium bromide, magnesium bromide, sodium iodide, potassium iodide, sodium sulfate, magnesium sulfate, zinc sulfate, rI & copper sulfate, sodium phosphate, potassium phosphate, sodium phosphite, calcium hypophosphite, Sodium hydroxide, lithium hydroxide, sodium stearate, magnesium stearate, aluminum stearate, zinc stearate, potassium oleate, sodium acetate, potassium acetate, sodium benzoate, sodium lauryl sulfonate, sodium benzene sulfonate, etc. It will be done. In addition, a metal base-containing compound capable of forming a polyamide, such as 5-sodium sulfoisophthalic acid, may be added to bond the metal base directly to the polyamide chain. The present invention contains a metal compound and has a specific melting resistance of 1-o at 260°C.
xto'Qcs or less (but not limited to the above metal compounds.Also, in the case of metals with low ionization potential such as alkali metals and alkaline earth metals, the length of the single substance should be 11. is also possible.

These metal compounds are added in an amount of 0.0005 to 3% by weight, preferably o, ooi, based on the polyamide resin.
It is desirable to contain it in an amount of up to 1% by weight.

If it is less than 0,0005% by weight, the amount of polyamide resin containing the metal compound must be increased in order to obtain sufficient electrostatic adhesion, and from the viewpoint of film performance and economical efficiency, Disadvantageous: Metal compound content is 3% by weight
In the above case, the physical properties of the film deteriorate, which is not preferable. However, the present invention is not limited to these metal compound content ranges.

The metal compound may be added to the raw material monomer before polymerization, during the progress of polymerization, during the extraction process, or when the pellets are dried. do not have. 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 film close to the rotating cooling roll, a method in which a corona discharge in a streamer corona state is applied to impart an electric charge (Japanese Patent Application Laid-open No. 55
-17559) is effective. However, the present invention is not limited to this method only (applying it to a device that applies a charge by bringing a normal high-voltage charging electrode close to a molten film, or applying it to an electrostatic adhesion device that uses an air knife in combination) ,
It is also possible to apply the present invention to a device in which a rotating cooling roll is covered with a power discharging body, and a charge having a sign opposite to that of a high-voltage charging electrode is deposited on the rotating cooling roll.

The take-up speed of the unstretched film in the present invention is not particularly limited. When the take-up speed is increased, air is caught between the rotating cooling roll and the molten film,
A uniform unstretched film cannot be obtained. For example, the specific melting resistance at 260°C without containing ordinary metal compounds is 1.
When polycapramide resin larger than 5 x 105 Ωl and with a metal/el extractable content of more than 1.5% by weight is drawn onto a rotary cooling roll by the electrostatic ejaculation method, the maximum drawing speed is usually 10 to 35 m/min. In contrast, in the present invention, air is prevented from being drawn in between the rotating cooling roll and the molten film even at this take-up speed or higher, and an unstretched film with a uniform thickness can be obtained. The unstretched polyamide as it is is suitable for packaging foods and the like. However, the unstretched polyamide film is further stretched 1.1 times or more in at least one direction, preferably 2 times or more in each of two orthogonal directions.
．． 0-5. Off! A biaxially stretched film obtained by stretching this film further improves mechanical strength, transparency, and oxygen barrier properties, and is suitable as a packaging film for each pole.

(Function) The function of the present invention will be explained below. Normally, static electricity V!
By applying a high voltage to the high-voltage charged electrode when winding the film onto a rotating cooling roll using the bone method, more charges can be applied to the molten film, resulting in greater electrostatic adhesion. However, if the applied high voltage is increased, dielectric breakdown occurs, so no higher voltage can be applied. Although the detailed fa structure is not clear, if a polycapramide resin with a methanol extractable content of 1.5 Wfi% or less is used in the present invention, the voltage applied to the high-voltage charged electrode can be higher than usual, and the take-up speed can be faster. However, air entrainment can be prevented and a uniform unstretched film can be obtained.Furthermore, by containing a metal compound and lowering the specific melting resistance of the resin, even at the same voltage, a higher charge can be produced in the melted film. It is believed that more electrostatic adhesion force can be obtained, and a higher take-up speed can be obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

The measurement methods used in the Examples and Comparative Examples are shown below.

(1) Melting specific resistance of raw material polycapramide resin 260
A stainless steel electrode was inserted into the molten resin kept at 1°C.
ov DC voltage is applied, and from the current value after 1 second to 5 seconds, specific resistance ρ = (S/L)X (V/I
) is the value calculated from the formula. Here, ρ is the specific resistance (Qc
s), S is the ffl pole area (cJ), and L is the interelectrode distance fi (
am), ■ represents voltage (V), and ■ represents current (A). S in the measurement in this example is 0.12cJ, L is 1.5c
It was m.

■ Methanol extraction of raw material polycapramide resin chips Grind raw material polycapramide resin chips,
．． Precisely weigh 5g of powder with a particle size of 0■■φ into the glass filter of a Nxley extractor and make 150ml! methanol was placed in a flask and soaked in a hot water bath at 95°C, and extracted for 24 hours. Filter FA'W! The I powder was dried under reduced pressure in a desiccator for 2 hours, then dried under reduced pressure at 105° C. for 15 hours, allowed to cool in the desiccator, accurately weighed, and calculated from ff1ffi before and after extraction using the following formula.

(Methanol extraction 10,000 anastomosis m> (3) Relative viscosity raw material polycapramide chips are added to 96.3% concentrated sulfuric acid for 1.
This value was measured using an Ostwald viscometer after dissolving at a concentration of 0 g/100 mff1 in a constant temperature bath at 20°C.

(4) Maximum take-up speed Using an extruder with a screw with a diameter of 90 cotton φ, T
The resin is extruded into a film from a die at 260-280°C, cast onto a rotating cooling roll at 10-20°C, a charge is applied to the molten film from a high-voltage charging electrode, and the film is tightly packed onto the rotating cooling roll, followed by rotating cooling. The take-up speed of the roll was gradually increased until the maximum take-up speed at which air could be prevented from being caught between the rotating cooling roll and the molten film was reached. Due to equipment limitations, measurements can be made up to 65 m/min, and if air entrainment can be prevented even then, 65 m/min.
It was more than a minute.

Example 1゜(Synthesis of polyamide resin containing metal compound) Nylon salt 80 obtained from Ajibi/@ and hexamethylene diamine
Polycondensation was carried out by adding 400 parts by weight and 3 parts by weight of sodium stearate to 0ff[ffi parts to obtain nylon 66 having a melt specific resistance of 0.14×10' Ocs and a relative viscosity of 2.6.

(Production of polyamide film) Next, silicon dioxide with a methanol extractable content of 0.8% by weight, a relative viscosity of 2.6, and an average particle size of 3 μm was used as a lubricant.
．． 100ff of polycapramide chips containing 4% by weight [
Six parts by weight of the above-mentioned nylon 66 chips containing calcium stearate were added to the storage section, and the chips were dried and mixed in a rotary vacuum chamber to determine the maximum take-up speed. Even at the maximum speed of 65 m/min, it was possible to prevent air from being entrained between the rotating cooling roll and the molten film. The melt specific resistance of this resin is 5
．． It was 5×10′Ω1.

Example 2 (Synthesis of polyamide resin containing metal compound) 5 parts by weight of trisodium phosphate dodecahydrate and 450 parts by weight of water were added to 440 mff of meta-xylene diamine and 470 parts by weight of adipic acid. Perform condensation to obtain 26
Polymethaxylylene adipamide having a melting specific resistance of 0.23×10'Ω at 0° C. and a relative viscosity of 2.1 was obtained.

(Formation of polyamide film) Next, a chip 10 of polycapramide having a methanol extractable content of 0.8% by weight, a relative viscosity of 2.6, and containing 0.4 weight ff 1% of silicon dioxide with an average particle size of 3 μm as a lubricant was prepared.
For each part of 0ff[ffi, add 1 chip of polymethaxylylene adipamide containing the above trisodium phosphate.
When the maximum take-up speed was determined using chips that had been dried and mixed in a rotary vacuum dryer, it was found that even at 65 m/min, which is the maximum usable speed of the device, there was no flow between the rotary cooling roll and the molten film. Air entrainment could be prevented. The melt specific resistance of this resin is 5.5X10'Ω1
Met.

Example & The same operation as Example 2 was performed except that 5 weight of calcium stearate was added instead of trisodium phosphate dodecahydrate in Example 2 to determine the maximum take-up speed, and it was found that it rotated up to 61 m/min. It was possible to prevent air from getting caught between the cooling roll and the molten film.

Comparative Example 1〜 Polycapramide chips containing 0.4ffIfi1% of silicon dioxide with a methanol extract having a substance content of 1.7% by weight, a relative viscosity of 2.6, and an average particle size of 3 μm were subjected to a normal hot water extraction process. When a casting test was conducted in the same manner as in Example 1, air was caught between the rotating cooling roll and the molten film at a speed of 35 m/min, and a uniform unstretched film could not be obtained at higher speeds. I couldn't.

Comparative Example 2 Polycapramide chips having a methanol extractable content of 0.8fffffi%, a relative viscosity of 2.6, and containing 0.4ffffft% of silicon dioxide with an average particle size of 3 μm as a lubricant were dried in a rotary vacuum dryer. After drying, the maximum take-up speed was determined using the chips as a raw material, and it was possible to prevent air from being drawn in between the rotating cooling roll and the molten film up to a speed of 47 m/min.

Comparative Example Except that in place of the polycapramide resin with a methanol extractable content of 0.8% by weight in Example 2, a polycapramide resin with a methanol extractable content of 1.7% by weight obtained by ordinary hot water extraction was used. When image formation was performed in the same manner as in Example 2, air was caught between the rotating cooling roll and the molten film at a speed of 49 m/min, and a uniform unstretched film could not be obtained at higher speeds.

The results of Examples 1 to 3 and Comparative Examples 1 to 2 are summarized in Table 1.

(Effects of the Invention) As is clear from the Examples, according to the present invention, a polycapramide film with excellent uniformity and transparency can be efficiently produced at high speed.

Patent Applicant Toyobo Co., Ltd. Procedure Amendment (Method) % Formula %! , Indication of the case Japanese Patent Application No. Sho 6O-16E3217 λ Title of the invention Method for producing polyamide film & Person making the amendment Relationship to the case Patent applicant No. 2-2-8 Dojimahama, Kita-ku, Osaka City Details of the invention in the specification Explanation Column 5, Contents of Amendment (1) Page 20 of the specification, "Table 1...Inscription for the entire table" is corrected as shown in the attached sheet.

that's all Manual continuation supplementary book January 13, 1985 1. Display of incident Patent application No. E30-168217 2 Name of the invention Manufacturing method of polyamide film 3. Person making the amendment Relationship to the case Patent applicant 2-2-8 Dojimahama, Kita-ku, Osaka (31fi) Toyobo Co., Ltd. Detailed description of the invention in the specification 5. Contents of amendment (1) The following parts of the description shall be corrected.

that's all

Claims (1)

[Scope of Claims] 1. Contains a metal compound and has a specific melting resistance of 1.0×1 at 260°C based on 100 parts by weight of a polycapramide resin with a methanol extractable content of 1.5% by weight or less
0^5Ωcm or less polyamide resin from 0.01 to 30
A method for producing a polyamide film, which comprises melt-extruding a composition blended in parts by weight into a film, electrostatically adhering the melt-extruded film to a rotating cooling roll, and taking it off while rapidly cooling and solidifying it to obtain a film. . 2. The obtained film is further processed in at least one direction by 1.1
A method for producing a polyamide film that is stretched more than twice as long.